Spring Boot Reference Guide
2.0.0.BUILD-SNAPSHOT
Copyright © 2012-2017
Table of Contents
- I. Spring Boot Documentation
- II. Getting Started
- III. Using Spring Boot
-
- 13. Build Systems
- 14. Structuring Your Code
- 15. Configuration Classes
- 16. Auto-configuration
- 17. Spring Beans and Dependency Injection
- 18. Using the @SpringBootApplication Annotation
- 19. Running Your Application
- 20. Developer Tools
- 21. Packaging Your Application for Production
- 22. What to Read Next
- IV. Spring Boot features
-
- 23. SpringApplication
- 24. Externalized Configuration
- 25. Profiles
- 26. Logging
- 27. Developing Web Applications
-
- 27.1. The ‘Spring Web MVC Framework’
-
- 27.1.1. Spring MVC Auto-configuration
- 27.1.2. HttpMessageConverters
- 27.1.3. Custom JSON Serializers and Deserializers
- 27.1.4. MessageCodesResolver
- 27.1.5. Static Content
- 27.1.6. Custom Favicon
- 27.1.7. ConfigurableWebBindingInitializer
- 27.1.8. Template Engines
- 27.1.9. Error Handling
- 27.1.10. Spring HATEOAS
- 27.1.11. CORS Support
- 27.2. The ‘Spring WebFlux Framework’
- 27.3. JAX-RS and Jersey
- 27.4. Embedded Servlet Container Support
- 28. Security
- 29. Working with SQL Databases
- 30. Working with NoSQL Technologies
- 31. Caching
- 32. Messaging
- 33. Calling REST Services with ‘RestTemplate’
- 34. Calling REST Services with ‘WebClient’
- 35. Validation
- 36. Sending Email
- 37. Distributed Transactions with JTA
- 38. Hazelcast
- 39. Quartz Scheduler
- 40. Spring Integration
- 41. Spring Session
- 42. Monitoring and Management over JMX
- 43. Testing
-
- 43.1. Test Scope Dependencies
- 43.2. Testing Spring Applications
- 43.3. Testing Spring Boot Applications
-
- 43.3.1. Detecting Test Configuration
- 43.3.2. Excluding Test Configuration
- 43.3.3. Working with Random Ports
- 43.3.4. Mocking and Spying Beans
- 43.3.5. Auto-configured Tests
- 43.3.6. Auto-configured JSON Tests
- 43.3.7. Auto-configured Spring MVC Tests
- 43.3.8. Auto-configured Spring WebFlux Tests
- 43.3.9. Auto-configured Data JPA Tests
- 43.3.10. Auto-configured JDBC Tests
- 43.3.11. Auto-configured jOOQ Tests
- 43.3.12. Auto-configured Data MongoDB Tests
- 43.3.13. Auto-configured Data Neo4j Tests
- 43.3.14. Auto-configured Data Redis Tests
- 43.3.15. Auto-configured Data LDAP Tests
- 43.3.16. Auto-configured REST Clients
- 43.3.17. Auto-configured Spring REST Docs Tests
- 43.3.18. User Configuration and Slicing
- 43.3.19. Using Spock to Test Spring Boot Applications
- 43.4. Test Utilities
- 44. WebSockets
- 45. Web Services
- 46. Creating Your Own Auto-configuration
- 47. What to Read Next
- V. Spring Boot Actuator: Production-ready features
-
- 48. Enabling Production-ready Features
- 49. Endpoints
- 50. Monitoring and Management over HTTP
- 51. Monitoring and Management over JMX
- 52. Loggers
- 53. Metrics
- 54. Auditing
- 55. Tracing
- 56. Process Monitoring
- 57. Cloud Foundry Support
- 58. What to Read Next
- VI. Deploying Spring Boot Applications
- VII. Spring Boot CLI
-
- 62. Installing the CLI
- 63. Using the CLI
- 64. Developing Applications with the Groovy Beans DSL
-
65. Configuring the CLI with
settings.xml - 66. What to Read Next
- VIII. Build tool plugins
- IX. ‘How-to’ guides
-
- 72. Spring Boot Application
- 73. Properties and Configuration
-
- 73.1. Automatically Expand Properties at Build Time
- 73.2. Externalize the Configuration of SpringApplication
- 73.3. Change the Location of External Properties of an Application
- 73.4. Use ‘Short’ Command Line Arguments
- 73.5. Use YAML for External Properties
- 73.6. Set the Active Spring Profiles
- 73.7. Change Configuration Depending on the Environment
- 73.8. Discover Built-in Options for External Properties
- 74. Embedded Web Servers
-
- 74.1. Use Another Web Server
- 74.2. Configure Jetty
- 74.3. Add a Servlet, Filter, or Listener to an Application
- 74.4. Change the HTTP Port
- 74.5. Use a Random Unassigned HTTP Port
- 74.6. Discover the HTTP Port at Runtime
- 74.7. Configure SSL
- 74.8. Configure HTTP/2
- 74.9. Configure Access Logging
- 74.10. Running Behind a Front-end Proxy Server
- 74.11. Configure Tomcat
- 74.12. Enable Multiple Connectors with Tomcat
- 74.13. Use Tomcat’s LegacyCookieProcessor
- 74.14. Configure Undertow
- 74.15. Enable Multiple Listeners with Undertow
- 74.16. Create WebSocket Endpoints Using @ServerEndpoint
- 74.17. Enable HTTP Response Compression
- 75. Spring MVC
-
- 75.1. Write a JSON REST Service
- 75.2. Write an XML REST Service
- 75.3. Customize the Jackson ObjectMapper
- 75.4. Customize the @ResponseBody Rendering
- 75.5. Handling Multipart File Uploads
- 75.6. Switch Off the Spring MVC DispatcherServlet
- 75.7. Switch off the Default MVC Configuration
- 75.8. Customize ViewResolvers
- 76. HTTP Clients
- 77. Logging
- 78. Data Access
-
- 78.1. Configure a Custom DataSource
- 78.2. Configure Two DataSources
- 78.3. Use Spring Data Repositories
- 78.4. Separate @Entity Definitions from Spring Configuration
- 78.5. Configure JPA Properties
- 78.6. Configure Hibernate Naming Strategy
- 78.7. Use a Custom EntityManagerFactory
- 78.8. Use Two EntityManagers
-
78.9. Use a Traditional
persistence.xmlFile - 78.10. Use Spring Data JPA and Mongo Repositories
- 78.11. Expose Spring Data Repositories as REST Endpoint
- 78.12. Configure a Component that is Used by JPA
- 79. Database Initialization
- 80. Messaging
- 81. Batch Applications
- 82. Actuator
- 83. Security
- 84. Hot Swapping
- 85. Build
-
- 85.1. Generate Build Information
- 85.2. Generate Git Information
- 85.3. Customize Dependency Versions
- 85.4. Create an Executable JAR with Maven
- 85.5. Use a Spring Boot Application as a Dependency
- 85.6. Extract Specific Libraries When an Executable Jar Runs
- 85.7. Create a Non-executable JAR with Exclusions
- 85.8. Remote Debug a Spring Boot Application Started with Maven
-
85.9. Build an Executable Archive from Ant without Using
spring-boot-antlib
- 86. Traditional Deployment
- X. Appendices
-
- A. Common application properties
- B. Configuration Metadata
- C. Auto-configuration classes
- D. Test auto-configuration annotations
- E. The Executable Jar Format
- F. Dependency versions
This section provides a brief overview of Spring Boot reference documentation. It serves as a map for the rest of the document.
The Spring Boot reference guide is available as
The latest copy is available at docs.spring.io/spring-boot/docs/current/reference.
Copies of this document may be made for your own use and for distribution to others, provided that you do not charge any fee for such copies and further provided that each copy contains this Copyright Notice, whether distributed in print or electronically.
If you have trouble with Spring Boot, we would like to help.
- Try the How-to documents. They provide solutions to the most common questions.
- Learn the Spring basics. Spring Boot builds on many other Spring projects. Check the spring.io web-site for a wealth of reference documentation. If you are starting out with Spring, try one of the guides.
- Ask a question. We monitor stackoverflow.com for questions tagged with
spring-boot. - Report bugs with Spring Boot at github.com/spring-projects/spring-boot/issues.
![[Note]](/image/aHR0cHM6Ly9kb2NzLnNwcmluZy5pby9zcHJpbmctYm9vdC9kb2NzL2N1cnJlbnQtU05BUFNIT1QvcmVmZXJlbmNlL2h0bWxzaW5nbGUvaW1hZ2VzL25vdGUucG5n.png) |
| All of Spring Boot is open source, including the documentation. If you find problems with the docs or if you want to improve them, please get involved. |
If you are getting started with Spring Boot or 'Spring' in general, start with the following topics:
- From scratch: Overview | Requirements | Installation
- Tutorial: Part 1 | Part 2
- Running your example: Part 1 | Part 2
Ready to actually start using Spring Boot? We have you covered:
- Build systems: Maven | Gradle | Ant | Starters
- Best practices: Code Structure | @Configuration | @EnableAutoConfiguration | Beans and Dependency Injection
- Running your code IDE | Packaged | Maven | Gradle
- Packaging your app: Production jars
- Spring Boot CLI: Using the CLI
Need more details about Spring Boot’s core features? The following content is for you:
- Core Features: SpringApplication | External Configuration | Profiles | Logging
- Web Applications: MVC | Embedded Containers
- Working with data: SQL | NO-SQL
- Messaging: Overview | JMS
- Testing: Overview | Boot Applications | Utils
- Extending: Auto-configuration | @Conditions
When you are ready to push your Spring Boot application to production, we have some tricks that you might like:
Finally, we have a few topics for more advanced users:
- Spring Boot Applications Deployment: Cloud Deployment | OS Service
- Build tool plugins: Maven | Gradle
- Appendix: Application Properties | Auto-configuration classes | Executable Jars
If you are getting started with Spring Boot, or "Spring" in general, start by reading this section. It answers the basic “what?”, “how?” and “why?” questions. It includes an introduction to Spring Boot, along with installation instructions. We then walk you through building your first Spring Boot application, discussing some core principles as we go.
Spring Boot makes it easy to create stand-alone, production-grade Spring based Applications that you can run. We take an opinionated view of the Spring platform and third-party libraries, so that you can get started with minimum fuss. Most Spring Boot applications need very little Spring configuration.
You can use Spring Boot to create Java applications that can be started by using java -jar or more traditional war deployments. We also provide a command line tool that runs “spring scripts”.
Our primary goals are:
- Provide a radically faster and widely accessible getting started experience for all Spring development.
- Be opinionated out of the box but get out of the way quickly as requirements start to diverge from the defaults.
- Provide a range of non-functional features that are common to large classes of projects (such as embedded servers, security, metrics, health checks, and externalized configuration).
- Absolutely no code generation and no requirement for XML configuration.
Spring Boot 2.0.0.BUILD-SNAPSHOT requires Java 8 and Spring Framework 5.0.2.BUILD-SNAPSHOT or above. Explicit build support is provided for Maven 3.2+ and Gradle 4.
Spring Boot can be used with “classic” Java development tools or installed as a command line tool. Either way, you need Java SDK v1.8 or higher. Before you begin, you should check your current Java installation by using the following command:
$ java -version
If you are new to Java development or if you want to experiment with Spring Boot, you might want to try the Spring Boot CLI (Command Line Interface) first, otherwise, read on for “classic” installation instructions.
You can use Spring Boot in the same way as any standard Java library. To do so, include the appropriate spring-boot-*.jar files on your classpath. Spring Boot does not require any special tools integration, so you can use any IDE or text editor. Also, there is nothing special about a Spring Boot application, so you can run and debug a Spring Boot application as you would any other Java program.
Although you could copy Spring Boot jars, we generally recommend that you use a build tool that supports dependency management (such as Maven or Gradle).
Spring Boot is compatible with Apache Maven 3.2 or above. If you do not already have Maven installed, you can follow the instructions at maven.apache.org.
![[Tip]](/image/aHR0cHM6Ly9kb2NzLnNwcmluZy5pby9zcHJpbmctYm9vdC9kb2NzL2N1cnJlbnQtU05BUFNIT1QvcmVmZXJlbmNlL2h0bWxzaW5nbGUvaW1hZ2VzL3RpcC5wbmc=.png) |
| On many operating systems, Maven can be installed with a package manager. If you use OSX Homebrew, try |
Spring Boot dependencies use the org.springframework.boot groupId. Typically, your Maven POM file inherits from the spring-boot-starter-parent project and declares dependencies to one or more “Starters”. Spring Boot also provides an optional Maven plugin to create executable jars.
The following listing shows a typical pom.xml file:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.example</groupId> <artifactId>myproject</artifactId> <version>0.0.1-SNAPSHOT</version> <!-- Inherit defaults from Spring Boot --> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.0.0.BUILD-SNAPSHOT</version> </parent> <!-- Add typical dependencies for a web application --> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> </dependencies> <!-- Package as an executable jar --> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build> <!-- Add Spring repositories --> <!-- (you don't need this if you are using a .RELEASE version) --> <repositories> <repository> <id>spring-snapshots</id> <url>http://repo.spring.io/snapshot</url> <snapshots><enabled>true</enabled></snapshots> </repository> <repository> <id>spring-milestones</id> <url>http://repo.spring.io/milestone</url> </repository> </repositories> <pluginRepositories> <pluginRepository> <id>spring-snapshots</id> <url>http://repo.spring.io/snapshot</url> </pluginRepository> <pluginRepository> <id>spring-milestones</id> <url>http://repo.spring.io/milestone</url> </pluginRepository> </pluginRepositories> </project>
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Spring Boot is compatible with Gradle 4. If you do not already have Gradle installed, you can follow the instructions at www.gradle.org/.
Spring Boot dependencies can be declared by using the org.springframework.boot group. Typically, your project declares dependencies to one or more “Starters”. Spring Boot provides a useful Gradle plugin that can be used to simplify dependency declarations and to create executable jars.
The following example shows a typical build.gradle file:
buildscript {
repositories {
jcenter()
maven { url 'http://repo.spring.io/snapshot' }
maven { url 'http://repo.spring.io/milestone' } } dependencies { classpath 'org.springframework.boot:spring-boot-gradle-plugin:2.0.0.BUILD-SNAPSHOT' } } apply plugin: 'java' apply plugin: 'org.springframework.boot' apply plugin: 'io.spring.dependency-management' jar { baseName = 'myproject' version = '0.0.1-SNAPSHOT' } repositories { jcenter() maven { url "http://repo.spring.io/snapshot" } maven { url "http://repo.spring.io/milestone" } } dependencies { compile("org.springframework.boot:spring-boot-starter-web") testCompile("org.springframework.boot:spring-boot-starter-test") }
The Spring Boot CLI (Command Line Interface) is a command line tool that you can use to quickly prototype with Spring. It lets you run Groovy scripts, which means that you have a familiar Java-like syntax without so much boilerplate code.
You do not need to use the CLI to work with Spring Boot, but it is definitely the quickest way to get a Spring application off the ground.
You can download the Spring CLI distribution from the Spring software repository:
Cutting edge snapshot distributions are also available.
Once downloaded, follow the INSTALL.txt instructions from the unpacked archive. In summary, there is a spring script (spring.bat for Windows) in a bin/ directory in the .zip file. Alternatively, you can use java -jar with the .jar file (the script helps you to be sure that the classpath is set correctly).
SDKMAN! (The Software Development Kit Manager) can be used for managing multiple versions of various binary SDKs, including Groovy and the Spring Boot CLI. Get SDKMAN! from sdkman.io and install Spring Boot by using the following commands:
$ sdk install springboot $ spring --version Spring Boot v2.0.0.BUILD-SNAPSHOT
If you are developing features for the CLI and want easy access to the version you built, use the following commands:
$ sdk install springboot dev /path/to/spring-boot/spring-boot-cli/target/spring-boot-cli-2.0.0.BUILD-SNAPSHOT-bin/spring-2.0.0.BUILD-SNAPSHOT/ $ sdk default springboot dev $ spring --version Spring CLI v2.0.0.BUILD-SNAPSHOT
The preceding instructions install a local instance of spring called the dev instance. It points at your target build location, so every time you rebuild Spring Boot,spring is up-to-date.
You can see it by running the following command:
$ sdk ls springboot ================================================================================ Available Springboot Versions ================================================================================ > + dev * 2.0.0.BUILD-SNAPSHOT ================================================================================ + - local version * - installed > - currently in use ================================================================================
If you are on a Mac and use Homebrew, you can install the Spring Boot CLI by using the following commands:
$ brew tap pivotal/tap $ brew install springboot
Homebrew installs spring to /usr/local/bin.
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| If you do not see the formula, your installation of brew might be out-of-date. In that case, run |
If you are on a Mac and use MacPorts, you can install the Spring Boot CLI by using the following command:
$ sudo port install spring-boot-cli
The Spring Boot CLI includes scripts that provide command completion for the BASH and zsh shells. You can source the script (also named spring) in any shell or put it in your personal or system-wide bash completion initialization. On a Debian system, the system-wide scripts are in /shell-completion/bash and all scripts in that directory are executed when a new shell starts. For example, to run the script manually if you have installed using SDKMAN!, use the following commands:
$ . ~/.sdkman/candidates/springboot/current/shell-completion/bash/spring $ spring <HIT TAB HERE> grab help jar run test version
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| If you install the Spring Boot CLI by using Homebrew or MacPorts, the command-line completion scripts are automatically registered with your shell. |
You can use the following web application to test your installation. To start, create a file called app.groovy, as follows:
@RestController class ThisWillActuallyRun { @RequestMapping("/") String home() { "Hello World!" } }
Then run it from a shell, as follows:
$ spring run app.groovy
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| The first run of your application is slow, as dependencies are downloaded. Subsequent runs are much quicker. |
Open localhost:8080 in your favorite web browser. You should see the following output:
Hello World!
If you are upgrading from an earlier release of Spring Boot check the “release notes” hosted on the project wiki. You’ll find upgrade instructions along with a list of “new and noteworthy” features for each release.
To upgrade an existing CLI installation use the appropriate package manager command (for example, brew upgrade) or, if you manually installed the CLI, follow thestandard instructions remembering to update your PATH environment variable to remove any older references.
This section describes how to develop a simple “Hello World!” web application that highlights some of Spring Boot’s key features. We use Maven to build this project, since most IDEs support it.
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| The spring.io web site contains many “Getting Started” guides that use Spring Boot. If you need to solve a specific problem, check there first. You can shortcut the steps below by going to start.spring.io and choosing the "Web" starter from the dependencies searcher. Doing so generates a new project structure so that you can start coding right away. Check the Spring Initializr documentation for more details. |
Before we begin, open a terminal and run the following commands to ensure that you have valid versions of Java and Maven installed:
$ java -version java version "1.8.0_102" Java(TM) SE Runtime Environment (build 1.8.0_102-b14) Java HotSpot(TM) 64-Bit Server VM (build 25.102-b14, mixed mode)
$ mvn -v Apache Maven 3.3.9 (bb52d8502b132ec0a5a3f4c09453c07478323dc5; 2015-11-10T16:41:47+00:00) Maven home: /usr/local/Cellar/maven/3.3.9/libexec Java version: 1.8.0_102, vendor: Oracle Corporation
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| This sample needs to be created in its own folder. Subsequent instructions assume that you have created a suitable folder and that it is your “current directory”. |
We need to start by creating a Maven pom.xml file. The pom.xml is the recipe that is used to build your project. Open your favorite text editor and add the following:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.example</groupId> <artifactId>myproject</artifactId> <version>0.0.1-SNAPSHOT</version> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.0.0.BUILD-SNAPSHOT</version> </parent> <!-- Additional lines to be added here... --> <!-- (you don't need this if you are using a .RELEASE version) --> <repositories> <repository> <id>spring-snapshots</id> <url>http://repo.spring.io/snapshot</url> <snapshots><enabled>true</enabled></snapshots> </repository> <repository> <id>spring-milestones</id> <url>http://repo.spring.io/milestone</url> </repository> </repositories> <pluginRepositories> <pluginRepository> <id>spring-snapshots</id> <url>http://repo.spring.io/snapshot</url> </pluginRepository> <pluginRepository> <id>spring-milestones</id> <url>http://repo.spring.io/milestone</url> </pluginRepository> </pluginRepositories> </project>
The preceding listing should give you a working build. You can test it by running mvn package (for now, you can ignore the “jar will be empty - no content was marked for inclusion!” warning).
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| At this point, you could import the project into an IDE (most modern Java IDEs include built-in support for Maven). For simplicity, we continue to use a plain text editor for this example. |
Spring Boot provides a number of “Starters” that let you add jars to your classpath. Our sample application has already used spring-boot-starter-parent in the parent section of the POM. The spring-boot-starter-parent is a special starter that provides useful Maven defaults. It also provides a dependency-managementsection so that you can omit version tags for “blessed” dependencies.
Other “Starters” provide dependencies that you are likely to need when developing a specific type of application. Since we are developing a web application, we add aspring-boot-starter-web dependency. Before that, we can look at what we currently have by running the following command:
$ mvn dependency:tree [INFO] com.example:myproject:jar:0.0.1-SNAPSHOT
The mvn dependency:tree command prints a tree representation of your project dependencies. You can see that spring-boot-starter-parent provides no dependencies by itself. To add the necessary dependencies, edit your pom.xml and add the spring-boot-starter-web dependency immediately below the parentsection:
<dependencies>
<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> </dependencies>
If you run mvn dependency:tree again, you see that there are now a number of additional dependencies, including the Tomcat web server and Spring Boot itself.
To finish our application, we need to create a single Java file. By default, Maven compiles sources from src/main/java, so you need to create that folder structure and then add a file named src/main/java/Example.java to contain the following code:
import org.springframework.boot.*;
import org.springframework.boot.autoconfigure.*; import org.springframework.web.bind.annotation.*; @RestController @EnableAutoConfiguration public class Example { @RequestMapping("/") String home() { return "Hello World!"; } public static void main(String[] args) throws Exception { SpringApplication.run(Example.class, args); } }
Although there is not much code here, quite a lot is going on. We step through the important parts in the next few sections.
The first annotation on our Example class is @RestController. This is known as a stereotype annotation. It provides hints for people reading the code and for Spring that the class plays a specific role. In this case, our class is a web @Controller, so Spring considers it when handling incoming web requests.
The @RequestMapping annotation provides “routing” information. It tells Spring that any HTTP request with the / path should be mapped to the home method. The@RestController annotation tells Spring to render the resulting string directly back to the caller.
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The second class-level annotation is @EnableAutoConfiguration. This annotation tells Spring Boot to “guess” how you want to configure Spring, based on the jar dependencies that you have added. Since spring-boot-starter-web added Tomcat and Spring MVC, the auto-configuration assumes that you are developing a web application and sets up Spring accordingly.
The final part of our application is the main method. This is just a standard method that follows the Java convention for an application entry point. Our main method delegates to Spring Boot’s SpringApplication class by calling run. SpringApplication bootstraps our application, starting Spring, which, in turn, starts the auto-configured Tomcat web server. We need to pass Example.class as an argument to the run method to tell SpringApplication which is the primary Spring component. The args array is also passed through to expose any command-line arguments.
At this point, your application should work. Since you used the spring-boot-starter-parent POM, you have a useful run goal that you can use to start the application. Type mvn spring-boot:run from the root project directory to start the application. You should see output similar to the following:
$ mvn spring-boot:run . ____ _ __ _ _ /\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \ ( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \ \\/ ___)| |_)| | | | | || (_| | ) ) ) ) ' |____| .__|_| |_|_| |_\__, | / / / / =========|_|==============|___/=/_/_/_/ :: Spring Boot :: (v2.0.0.BUILD-SNAPSHOT) ....... . . . ....... . . . (log output here) ....... . . . ........ Started Example in 2.222 seconds (JVM running for 6.514)
If you open a web browser to localhost:8080, you should see the following output:
Hello World!
To gracefully exit the application, press ctrl-c.
We finish our example by creating a completely self-contained executable jar file that we could run in production. Executable jars (sometimes called “fat jars”) are archives containing your compiled classes along with all of the jar dependencies that your code needs to run.
To create an executable jar, we need to add the spring-boot-maven-plugin to our pom.xml. To do so, insert the following lines just below the dependenciessection:
<build>
<plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build>
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Save your pom.xml and run mvn package from the command line, as follows:
$ mvn package [INFO] Scanning for projects... [INFO] [INFO] ------------------------------------------------------------------------ [INFO] Building myproject 0.0.1-SNAPSHOT [INFO] ------------------------------------------------------------------------ [INFO] .... .. [INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ myproject --- [INFO] Building jar: /Users/developer/example/spring-boot-example/target/myproject-0.0.1-SNAPSHOT.jar [INFO] [INFO] --- spring-boot-maven-plugin:2.0.0.BUILD-SNAPSHOT:repackage (default) @ myproject --- [INFO] ------------------------------------------------------------------------ [INFO] BUILD SUCCESS [INFO] ------------------------------------------------------------------------
If you look in the target directory, you should see myproject-0.0.1-SNAPSHOT.jar. The file should be around 10 MB in size. If you want to peek inside, you can use jar tvf, as follows:
$ jar tvf target/myproject-0.0.1-SNAPSHOT.jar
You should also see a much smaller file named myproject-0.0.1-SNAPSHOT.jar.original in the target directory. This is the original jar file that Maven created before it was repackaged by Spring Boot.
To run that application, use the java -jar command, as follows:
$ java -jar target/myproject-0.0.1-SNAPSHOT.jar . ____ _ __ _ _ /\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \ ( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \ \\/ ___)| |_)| | | | | || (_| | ) ) ) ) ' |____| .__|_| |_|_| |_\__, | / / / / =========|_|==============|___/=/_/_/_/ :: Spring Boot :: (v2.0.0.BUILD-SNAPSHOT) ....... . . . ....... . . . (log output here) ....... . . . ........ Started Example in 2.536 seconds (JVM running for 2.864)
As before, to exit the application, press ctrl-c.
Hopefully, this section provided some of the Spring Boot basics and got you on your way to writing your own applications. If you are a task-oriented type of developer, you might want to jump over to spring.io and check out some of the getting started guides that solve specific “How do I do that with Spring?” problems. We also have Spring Boot-specific “How-to” reference documentation.
The Spring Boot repository also has a bunch of samples you can run. The samples are independent of the rest of the code (that is, you do not need to build the rest to run or use the samples).
Otherwise, the next logical step is to read Part III, “Using Spring Boot”. If you are really impatient, you could also jump ahead and read about Spring Boot features.
This section goes into more detail about how you should use Spring Boot. It covers topics such as build systems, auto-configuration, and how to run your applications. We also cover some Spring Boot best practices. Although there is nothing particularly special about Spring Boot (it is just another library that you can consume), there are a few recommendations that, when followed, make your development process a little easier.
If you are starting out with Spring Boot, you should probably read the Getting Started guide before diving into this section.
It is strongly recommended that you choose a build system that supports dependency management and that can consume artifacts published to the “Maven Central” repository. We would recommend that you choose Maven or Gradle. It is possible to get Spring Boot to work with other build systems (Ant, for example), but they are not particularly well supported.
Each release of Spring Boot provides a curated list of dependencies that it supports. In practice, you do not need to provide a version for any of these dependencies in your build configuration, as Spring Boot is managing that for you. When you upgrade Spring Boot itself, these dependencies are upgraded as well in a consistent way.
|
| You can still specify a version and override Spring Boot’s recommendations if you need to do so. |
The curated list contains all the spring modules that you can use with Spring Boot as well as a refined list of third party libraries. The list is available as a standard Bills of Materials (spring-boot-dependencies) that can be used with both Maven and Gradle.
![[Warning]](/image/aHR0cHM6Ly9kb2NzLnNwcmluZy5pby9zcHJpbmctYm9vdC9kb2NzL2N1cnJlbnQtU05BUFNIT1QvcmVmZXJlbmNlL2h0bWxzaW5nbGUvaW1hZ2VzL3dhcm5pbmcucG5n.png) |
| Each release of Spring Boot is associated with a base version of the Spring Framework. We highly recommend that you not specify its version. |
Maven users can inherit from the spring-boot-starter-parent project to obtain sensible defaults. The parent project provides the following features:
- Java 1.8 as the default compiler level.
- UTF-8 source encoding.
- A Dependency Management section, inherited from the spring-boot-dependencies pom, that manages the versions of common dependencies. This dependency management lets you omit <version> tags for those dependencies when used in your own pom.
- Sensible resource filtering.
- Sensible plugin configuration (exec plugin, Git commit ID, and shade).
- Sensible resource filtering for
application.propertiesandapplication.ymlincluding profile-specific files (for example,application-foo.propertiesandapplication-foo.yml)
Note that, since the application.properties and application.yml files accept Spring style placeholders (${…}), the Maven filtering is changed to use @..@placeholders. (You can override that by setting a Maven property called resource.delimiter.)
To configure your project to inherit from the spring-boot-starter-parent set the parent, as follows:
<!-- Inherit defaults from Spring Boot -->
<parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.0.0.BUILD-SNAPSHOT</version> </parent>
|
| You should need to specify only the Spring Boot version number on this dependency. If you import additional starters, you can safely omit the version number. |
With that setup, you can also override individual dependencies by overriding a property in your own project. For instance, to upgrade to another Spring Data release train, you would add the following to your pom.xml:
<properties>
<spring-data-releasetrain.version>Fowler-SR2</spring-data-releasetrain.version> </properties>
|
| Check the |
Not everyone likes inheriting from the spring-boot-starter-parent POM. You may have your own corporate standard parent that you need to use or you may prefer to explicitly declare all your Maven configuration.
If you do not want to use the spring-boot-starter-parent, you can still keep the benefit of the dependency management (but not the plugin management) by using ascope=import dependency, as follows:
<dependencyManagement>
<dependencies> <dependency> <!-- Import dependency management from Spring Boot --> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-dependencies</artifactId> <version>2.0.0.BUILD-SNAPSHOT</version> <type>pom</type> <scope>import</scope> </dependency> </dependencies> </dependencyManagement>
The preceding sample setup does not let you override individual dependencies by using a property, as explained above. To achieve the same result, you need to add an entry in the dependencyManagement of your project before the spring-boot-dependencies entry. For instance, to upgrade to another Spring Data release train, you could add the following element to your pom.xml:
<dependencyManagement>
<dependencies> <!-- Override Spring Data release train provided by Spring Boot --> <dependency> <groupId>org.springframework.data</groupId> <artifactId>spring-data-releasetrain</artifactId> <version>Fowler-SR2</version> <scope>import</scope> <type>pom</type> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-dependencies</artifactId> <version>2.0.0.BUILD-SNAPSHOT</version> <type>pom</type> <scope>import</scope> </dependency> </dependencies> </dependencyManagement>
|
| In the preceding example, we specify a BOM, but any dependency type can be overridden in the same way. |
Spring Boot includes a Maven plugin that can package the project as an executable jar. Add the plugin to your <plugins> section if you want to use it, as shown in the following example:
<build>
<plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build>
|
| If you use the Spring Boot starter parent pom, you need to add only the plugin. There is no need to configure it unless you want to change the settings defined in the parent. |
To learn about using Spring Boot with Gradle, please refer to the documentation for Spring Boot’s Gradle plugin:
It is possible to build a Spring Boot project using Apache Ant+Ivy. The spring-boot-antlib “AntLib” module is also available to help Ant create executable jars.
To declare dependencies, a typical ivy.xml file looks something like the following example:
<ivy-module version="2.0"> <info organisation="org.springframework.boot" module="spring-boot-sample-ant" /> <configurations> <conf name="compile" description="everything needed to compile this module" /> <conf name="runtime" extends="compile" description="everything needed to run this module" /> </configurations> <dependencies> <dependency org="org.springframework.boot" name="spring-boot-starter" rev="${spring-boot.version}" conf="compile" /> </dependencies> </ivy-module>
A typical build.xml looks like the following example:
<project
xmlns:ivy="antlib:org.apache.ivy.ant" xmlns:spring-boot="antlib:org.springframework.boot.ant" name="myapp" default="build"> <property name="spring-boot.version" value="2.0.0.BUILD-SNAPSHOT" /> <target name="resolve" description="--> retrieve dependencies with ivy"> <ivy:retrieve pattern="lib/[conf]/[artifact]-[type]-[revision].[ext]" /> </target> <target name="classpaths" depends="resolve"> <path id="compile.classpath"> <fileset dir="lib/compile" includes="*.jar" /> </path> </target> <target name="init" depends="classpaths"> <mkdir dir="build/classes" /> </target> <target name="compile" depends="init" description="compile"> <javac srcdir="src/main/java" destdir="build/classes" classpathref="compile.classpath" /> </target> <target name="build" depends="compile"> <spring-boot:exejar destfile="build/myapp.jar" classes="build/classes"> <spring-boot:lib> <fileset dir="lib/runtime" /> </spring-boot:lib> </spring-boot:exejar> </target> </project>
|
| If you do not want to use the |
Starters are a set of convenient dependency descriptors that you can include in your application. You get a one-stop shop for all the Spring and related technology that you need without having to hunt through sample code and copy-paste loads of dependency descriptors. For example, if you want to get started using Spring and JPA for database access, include the spring-boot-starter-data-jpa dependency in your project.
The starters contain a lot of the dependencies that you need to get a project up and running quickly and with a consistent, supported set of managed transitive dependencies.
The following application starters are provided by Spring Boot under the org.springframework.boot group:
Table 13.1. Spring Boot application starters
| Name | Description | Pom |
|---|---|---|
| Core starter, including auto-configuration support, logging and YAML |
||
| Starter for JMS messaging using Apache ActiveMQ |
||
| Starter for using Spring AMQP and Rabbit MQ |
||
| Starter for aspect-oriented programming with Spring AOP and AspectJ |
||
| Starter for JMS messaging using Apache Artemis |
||
| Starter for using Spring Batch |
||
| Starter for using Spring Framework’s caching support |
||
| Starter for using Spring Cloud Connectors which simplifies connecting to services in cloud platforms like Cloud Foundry and Heroku |
||
| Starter for using Cassandra distributed database and Spring Data Cassandra |
||
| Starter for using Cassandra distributed database and Spring Data Cassandra Reactive |
||
| Starter for using Couchbase document-oriented database and Spring Data Couchbase |
||
| Starter for using Couchbase document-oriented database and Spring Data Couchbase Reactive |
||
| Starter for using Elasticsearch search and analytics engine and Spring Data Elasticsearch |
||
| Starter for using Spring Data JPA with Hibernate |
||
| Starter for using Spring Data LDAP |
||
| Starter for using MongoDB document-oriented database and Spring Data MongoDB |
||
| Starter for using MongoDB document-oriented database and Spring Data MongoDB Reactive |
||
| Starter for using Neo4j graph database and Spring Data Neo4j |
||
| Starter for using Redis key-value data store with Spring Data Redis and the Lettuce client |
||
| Starter for using Redis key-value data store with Spring Data Redis reactive and the Lettuce client |
||
| Starter for exposing Spring Data repositories over REST using Spring Data REST |
||
| Starter for using the Apache Solr search platform with Spring Data Solr |
||
| Starter for building MVC web applications using FreeMarker views |
||
| Starter for building MVC web applications using Groovy Templates views |
||
| Starter for building hypermedia-based RESTful web application with Spring MVC and Spring HATEOAS |
||
| Starter for using Spring Integration |
||
| Starter for using JDBC with the Tomcat JDBC connection pool |
||
| Starter for building RESTful web applications using JAX-RS and Jersey. An alternative to |
||
| Starter for using jOOQ to access SQL databases. An alternative to |
||
| Starter for reading and writing json |
||
| Starter for JTA transactions using Atomikos |
||
| Starter for JTA transactions using Bitronix |
||
| Spring Boot Narayana JTA Starter |
||
| Starter for using Java Mail and Spring Framework’s email sending support |
||
| Starter for building web applications using Mustache views |
||
| Spring Boot Quartz Starter |
||
| Starter for using Spring Security |
||
| Starter for using Spring Social Facebook |
||
| Stater for using Spring Social LinkedIn |
||
| Starter for using Spring Social Twitter |
||
| Starter for testing Spring Boot applications with libraries including JUnit, Hamcrest and Mockito |
||
| Starter for building MVC web applications using Thymeleaf views |
||
| Starter for using Java Bean Validation with Hibernate Validator |
||
| Starter for building web, including RESTful, applications using Spring MVC. Uses Tomcat as the default embedded container |
||
| Starter for using Spring Web Services |
||
| Starter for building WebFlux applications using Spring Framework’s Reactive Web support |
||
| Starter for building WebSocket applications using Spring Framework’s WebSocket support |
In addition to the application starters, the following starters can be used to add production ready features:
Table 13.2. Spring Boot production starters
| Name | Description | Pom |
|---|---|---|
| Starter for using Spring Boot’s Actuator which provides production ready features to help you monitor and manage your application |
Finally, Spring Boot also includes the following starters that can be used if you want to exclude or swap specific technical facets:
Table 13.3. Spring Boot technical starters
| Name | Description | Pom |
|---|---|---|
| Starter for using Jetty as the embedded servlet container. An alternative to |
||
| Starter for using Log4j2 for logging. An alternative to |
||
| Starter for logging using Logback. Default logging starter |
||
| Starter for using Reactor Netty as the embedded reactive HTTP server. |
||
| Starter for using Tomcat as the embedded servlet container. Default servlet container starter used by |
||
| Starter for using Undertow as the embedded servlet container. An alternative to |
|
| For a list of additional community contributed starters, see the README file in the |
Spring Boot does not require any specific code layout to work. However, there are some best practices that help.
When a class does not include a package declaration, it is considered to be in the “default package”. The use of the “default package” is generally discouraged and should be avoided. It can cause particular problems for Spring Boot applications that use the @ComponentScan, @EntityScan, or @SpringBootApplicationannotations, since every class from every jar is read.
|
| We recommend that you follow Java’s recommended package naming conventions and use a reversed domain name (for example, |
We generally recommend that you locate your main application class in a root package above other classes. The @EnableAutoConfiguration annotation is often placed on your main class, and it implicitly defines a base “search package” for certain items. For example, if you are writing a JPA application, the package of the@EnableAutoConfiguration annotated class is used to search for @Entity items.
Using a root package also lets the @ComponentScan annotation be used without needing to specify a basePackage attribute. You can also use the @SpringBootApplication annotation if your main class is in the root package.
The following listing shows a typical layout:
com
+- example
+- myapplication
+- Application.java
|
+- customer
| +- Customer.java
| +- CustomerController.java
| +- CustomerService.java
| +- CustomerRepository.java
|
+- order
+- Order.java
+- OrderController.java
+- OrderService.java
+- OrderRepository.java
The Application.java file would declare the main method, along with the basic @Configuration, as follows:
package com.example.myapplication;
import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.EnableAutoConfiguration; import org.springframework.context.annotation.ComponentScan; import org.springframework.context.annotation.Configuration; @Configuration @EnableAutoConfiguration @ComponentScan public class Application { public static void main(String[] args) { SpringApplication.run(Application.class, args); } }
Spring Boot favors Java-based configuration. Although it is possible to use SpringApplication with XML sources, we generally recommend that your primary source be a single @Configuration class. Usually the class that defines the main method is a good candidate as the primary @Configuration.
|
| Many Spring configuration examples have been published on the Internet that use XML configuration. If possible, always try to use the equivalent Java-based configuration. Searching for |
You need not put all your @Configuration into a single class. The @Import annotation can be used to import additional configuration classes. Alternatively, you can use @ComponentScan to automatically pick up all Spring components, including @Configuration classes.
Spring Boot auto-configuration attempts to automatically configure your Spring application based on the jar dependencies that you have added. For example, if HSQLDBis on your classpath, and you have not manually configured any database connection beans, then Spring Boot auto-configures an in-memory database.
You need to opt-in to auto-configuration by adding the @EnableAutoConfiguration or @SpringBootApplication annotations to one of your @Configurationclasses.
|
| You should only ever add one |
Auto-configuration is non-invasive. At any point, you can start to define your own configuration to replace specific parts of the auto-configuration. For example, if you add your own DataSource bean, the default embedded database support backs away.
If you need to find out what auto-configuration is currently being applied, and why, start your application with the --debug switch. Doing so enables debug logs for a selection of core loggers and logs a conditions report to the console.
If you find that specific auto-configuration classes that you do not want are being applied, you can use the exclude attribute of @EnableAutoConfiguration to disable them, as shown in the following example:
import org.springframework.boot.autoconfigure.*;
import org.springframework.boot.autoconfigure.jdbc.*; import org.springframework.context.annotation.*; @Configuration @EnableAutoConfiguration(exclude={DataSourceAutoConfiguration.class}) public class MyConfiguration { }
If the class is not on the classpath, you can use the excludeName attribute of the annotation and specify the fully qualified name instead. Finally, you can also control the list of auto-configuration classes to exclude by using the spring.autoconfigure.exclude property.
|
| You can define exclusions both at the annotation level and by using the property. |
You are free to use any of the standard Spring Framework techniques to define your beans and their injected dependencies. For simplicity, we often find that using@ComponentScan (to find your beans) and using @Autowired (to do constructor injection) works well.
If you structure your code as suggested above (locating your application class in a root package), you can add @ComponentScan without any arguments. All of your application components (@Component, @Service, @Repository, @Controller etc.) are automatically registered as Spring Beans.
The following example shows a @Service Bean that uses constructor injection to obtain a required RiskAssessor bean:
package com.example.service;
import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Service; @Service public class DatabaseAccountService implements AccountService { private final RiskAssessor riskAssessor; @Autowired public DatabaseAccountService(RiskAssessor riskAssessor) { this.riskAssessor = riskAssessor; } // ... }
If a bean has one constructor, you can omit the @Autowired, as shown in the following example:
@Service public class DatabaseAccountService implements AccountService { private final RiskAssessor riskAssessor; public DatabaseAccountService(RiskAssessor riskAssessor) { this.riskAssessor = riskAssessor; } // ... }
|
| Notice how using constructor injection lets the |
Many Spring Boot developers always have their main class annotated with @Configuration, @EnableAutoConfiguration, and @ComponentScan. Since these annotations are so frequently used together (especially if you follow the best practices above), Spring Boot provides a convenient @SpringBootApplicationalternative.
The @SpringBootApplication annotation is equivalent to using @Configuration, @EnableAutoConfiguration, and @ComponentScan with their default attributes, as shown in the following example:
package com.example.myapplication;
import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; @SpringBootApplication // same as @Configuration @EnableAutoConfiguration @ComponentScan public class Application { public static void main(String[] args) { SpringApplication.run(Application.class, args); } }
|
|
|
One of the biggest advantages of packaging your application as a jar and using an embedded HTTP server is that you can run your application as you would any other. Debugging Spring Boot applications is also easy. You do not need any special IDE plugins or extensions.
|
| This section only covers jar based packaging. If you choose to package your application as a war file, you should refer to your server and IDE documentation. |
You can run a Spring Boot application from your IDE as a simple Java application. However, you first need to import your project. Import steps vary depending on your IDE and build system. Most IDEs can import Maven projects directly. For example, Eclipse users can select Import… → Existing Maven Projects from the Filemenu.
If you cannot directly import your project into your IDE, you may be able to generate IDE metadata by using a build plugin. Maven includes plugins for Eclipse and IDEA. Gradle offers plugins for various IDEs.
|
| If you accidentally run a web application twice, you see a “Port already in use” error. STS users can use the |
If you use the Spring Boot Maven or Gradle plugins to create an executable jar, you can run your application using java -jar, as shown in the following example:
$ java -jar target/myapplication-0.0.1-SNAPSHOT.jar
It is also possible to run a packaged application with remote debugging support enabled. Doing so lets you attach a debugger to your packaged application, as shown in the following example:
$ java -Xdebug -Xrunjdwp:server=y,transport=dt_socket,address=8000,suspend=n \
-jar target/myapplication-0.0.1-SNAPSHOT.jar
The Spring Boot Maven plugin includes a run goal that can be used to quickly compile and run your application. Applications run in an exploded form, as they do in your IDE.
$ mvn spring-boot:run
You might also want to use the MAVEN_OPTS operating system environment variable, as shown in the following example:
$ export MAVEN_OPTS=-Xmx1024m
The Spring Boot Gradle plugin also includes a bootRun task that can be used to run your application in an exploded form. The bootRun task is added whenever you apply the org.springframework.boot and java plugins and is shown in the following example:
$ gradle bootRun
You might also want to use the JAVA_OPTS operating system environment variable, as shown in the following example:
$ export JAVA_OPTS=-Xmx1024m
Since Spring Boot applications are just plain Java applications, JVM hot-swapping should work out of the box. JVM hot swapping is somewhat limited with the bytecode that it can replace. For a more complete solution, JRebel can be used.
The spring-boot-devtools module also includes support for quick application restarts. See the Chapter 20, Developer Tools section below and the Hot swapping “How-to” for details.
Spring Boot includes an additional set of tools that can make the application development experience a little more pleasant. The spring-boot-devtools module can be included in any project to provide additional development-time features. To include devtools support, add the module dependency to your build, as shown in the following listings for Maven and Gradle:
Maven.
<dependencies>
<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-devtools</artifactId> <optional>true</optional> </dependency> </dependencies>
Gradle.
dependencies {
compile("org.springframework.boot:spring-boot-devtools")
}
|
| Developer tools are automatically disabled when running a fully packaged application. If your application is launched using |
|
| Repackaged archives do not contain devtools by default. If you want to use a certain remote devtools feature, you need to disable the |
Several of the libraries supported by Spring Boot use caches to improve performance. For example, template engines cache compiled templates to avoid repeatedly parsing template files. Also, Spring MVC can add HTTP caching headers to responses when serving static resources.
While caching is very beneficial in production, it can be counter-productive during development, preventing you from seeing the changes you just made in your application. For this reason, spring-boot-devtools disables the caching options by default.
Cache options are usually configured by settings in your application.properties file. For example, Thymeleaf offers the spring.thymeleaf.cache property. Rather than needing to set these properties manually, the spring-boot-devtools module automatically applies sensible development-time configuration.
|
| For a complete list of the properties that are applied by the devtools, see DevToolsPropertyDefaultsPostProcessor. |
Applications that use spring-boot-devtools automatically restart whenever files on the classpath change. This can be a useful feature when working in an IDE, as it gives a very fast feedback loop for code changes. By default, any entry on the classpath that points to a folder is monitored for changes. Note that certain resources, such as static assets and view templates, do not need to restart the application.
|
| As long as forking is enabled, you can also start your application by using the supported build plugins (Maven and Gradle), since DevTools needs an isolated application classloader to operate properly. By default, Gradle and Maven do that when they detect DevTools on the classpath. |
|
| Automatic restart works very well when used with LiveReload. See the LiveReload section for details. If you use JRebel, automatic restarts are disabled in favor of dynamic class reloading. Other devtools features (such as LiveReload and property overrides) can still be used. |
|
| DevTools relies on the application context’s shutdown hook to close it during a restart. It does not work correctly if you have disabled the shutdown hook ( |
|
| When deciding if an entry on the classpath should trigger a restart when it changes, DevTools automatically ignores projects named |
|
| DevTools needs to customize the |
Certain resources do not necessarily need to trigger a restart when they are changed. For example, Thymeleaf templates can be edited in-place. By default, changing resources in /META-INF/maven, /META-INF/resources, /resources, /static, /public, or /templates does not trigger a restart but does trigger a live reload. If you want to customize these exclusions, you can use the spring.devtools.restart.exclude property. For example, to exclude only /static and /public you would set the following property:
spring.devtools.restart.exclude=static/**,public/**
|
| If you want to keep those defaults and add additional exclusions, use the |
You may want your application to be restarted or reloaded when you make changes to files that are not on the classpath. To do so, use thespring.devtools.restart.additional-paths property to configure additional paths to watch for changes. You can use the spring.devtools.restart.excludeproperty described above to control whether changes beneath the additional paths trigger a full restart or a live reload.
If you do not want to use the restart feature, you can disable it by using the spring.devtools.restart.enabled property. In most cases, you can set this property in your application.properties (doing so still initializes the restart classloader, but it does not watch for file changes).
If you need to completely disable restart support (for example, because it doesn’t work with a specific library), you need to set the spring.devtools.restart.enabledSystem property to false before calling SpringApplication.run(…), as shown in the following example:
public static void main(String[] args) { System.setProperty("spring.devtools.restart.enabled", "false"); SpringApplication.run(MyApp.class, args); }
If you work with an IDE that continuously compiles changed files, you might prefer to trigger restarts only at specific times. To do so, you can use a “trigger file”, which is a special file that must be modified when you want to actually trigger a restart check. Changing the file only triggers the check and the restart will only occur if Devtools has detected it has to do something. The trigger file can be updated manually or with an IDE plugin.
To use a trigger file, set the spring.devtools.restart.trigger-file property to the path of your trigger file.
|
| You might want to set |
As described in the Restart vs Reload section above, restart functionality is implemented by using two classloaders. For most applications, this approach works well. However, sometimes it can cause classloading issues.
By default, any open project in your IDE is loaded with the “restart” classloader, and any regular .jar file is loaded with the “base” classloader. If you work on a multi-module project, and not every module is imported into your IDE, you may need to customize things. To do so, you can create a META-INF/spring-devtools.properties file.
The spring-devtools.properties file can contain properties prefixed with restart.exclude and restart.include. The include elements are items that should be pulled up into the “restart” classloader, and the exclude elements are items that should be pushed down into the “base” classloader. The value of the property is a regex pattern that is applied to the classpath, as shown in the following example:
restart.exclude.companycommonlibs=/mycorp-common-[\\w-]+\.jar
restart.include.projectcommon=/mycorp-myproj-[\\w-]+\.jar
|
| All property keys must be unique. As long as a property starts with |
|
| All |
Restart functionality does not work well with objects that are deserialized by using a standard ObjectInputStream. If you need to deserialize data, you may need to use Spring’s ConfigurableObjectInputStream in combination with Thread.currentThread().getContextClassLoader().
Unfortunately, several third-party libraries deserialize without considering the context classloader. If you find such a problem, you need to request a fix with the original authors.
The spring-boot-devtools module includes an embedded LiveReload server that can be used to trigger a browser refresh when a resource is changed. LiveReload browser extensions are freely available for Chrome, Firefox and Safari from livereload.com.
If you do not want to start the LiveReload server when your application runs, you can set the spring.devtools.livereload.enabled property to false.
|
| You can only run one LiveReload server at a time. Before starting your application, ensure that no other LiveReload servers are running. If you start multiple applications from your IDE, only the first has LiveReload support. |
You can configure global devtools settings by adding a file named .spring-boot-devtools.properties to your $HOME folder (note that the filename starts with “.”). Any properties added to this file apply to all Spring Boot applications on your machine that use devtools. For example, to configure restart to always use a trigger file, you would add the following property:
~/.spring-boot-devtools.properties.
spring.devtools.reload.trigger-file=.reloadtrigger
The Spring Boot developer tools are not just limited to local development. You can also use several features when running applications remotely. Remote support is opt-in. To enable it, you need to make sure that devtools is included in the repackaged archive, as shown in the following listing:
<build>
<plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> <configuration> <excludeDevtools>false</excludeDevtools> </configuration> </plugin> </plugins> </build>
Then you need to set a spring.devtools.remote.secret property, as shown in the following example:
spring.devtools.remote.secret=mysecret
|
| Enabling |
Remote devtools support is provided in two parts: a server-side endpoint that accepts connections and a client application that you run in your IDE. The server component is automatically enabled when the spring.devtools.remote.secret property is set. The client component must be launched manually.
The remote client application is designed to be run from within your IDE. You need to run org.springframework.boot.devtools.RemoteSpringApplication with the same classpath as the remote project that you connect to. The application’s single required argument is the remote URL to which it connects.
For example, if you are using Eclipse or STS and you have a project named my-app that you have deployed to Cloud Foundry, you would do the following:
- Select
Run Configurations…from theRunmenu. - Create a new
Java Application“launch configuration”. - Browse for the
my-appproject. - Use
org.springframework.boot.devtools.RemoteSpringApplicationas the main class. - Add
https://myapp.cfapps.ioto theProgram arguments(or whatever your remote URL is).
A running remote client might resemble the following listing:
. ____ _ __ _ _ /\\ / ___'_ __ _ _(_)_ __ __ _ ___ _ \ \ \ \ ( ( )\___ | '_ | '_| | '_ \/ _` | | _ \___ _ __ ___| |_ ___ \ \ \ \ \\/ ___)| |_)| | | | | || (_| []::::::[] / -_) ' \/ _ \ _/ -_) ) ) ) ) ' |____| .__|_| |_|_| |_\__, | |_|_\___|_|_|_\___/\__\___|/ / / / =========|_|==============|___/===================================/_/_/_/ :: Spring Boot Remote :: 2.0.0.BUILD-SNAPSHOT 2015-06-10 18:25:06.632 INFO 14938 --- [ main] o.s.b.devtools.RemoteSpringApplication : Starting RemoteSpringApplication on pwmbp with PID 14938 (/Users/pwebb/projects/spring-boot/code/spring-boot-devtools/target/classes started by pwebb in /Users/pwebb/projects/spring-boot/code/spring-boot-samples/spring-boot-sample-devtools) 2015-06-10 18:25:06.671 INFO 14938 --- [ main] s.c.a.AnnotationConfigApplicationContext : Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@2a17b7b6: startup date [Wed Jun 10 18:25:06 PDT 2015]; root of context hierarchy 2015-06-10 18:25:07.043 WARN 14938 --- [ main] o.s.b.d.r.c.RemoteClientConfiguration : The connection to http://localhost:8080 is insecure. You should use a URL starting with 'https://'. 2015-06-10 18:25:07.074 INFO 14938 --- [ main] o.s.b.d.a.OptionalLiveReloadServer : LiveReload server is running on port 35729 2015-06-10 18:25:07.130 INFO 14938 --- [ main] o.s.b.devtools.RemoteSpringApplication : Started RemoteSpringApplication in 0.74 seconds (JVM running for 1.105)
|
| Because the remote client is using the same classpath as the real application it can directly read application properties. This is how the |
|
| It is always advisable to use |
|
| If you need to use a proxy to access the remote application, configure the |
The remote client monitors your application classpath for changes in the same way as the local restart. Any updated resource is pushed to the remote application and (if required) triggers a restart. This can be helpful if you iterate on a feature that uses a cloud service that you do not have locally. Generally, remote updates and restarts are much quicker than a full rebuild and deploy cycle.
|
| Files are only monitored when the remote client is running. If you change a file before starting the remote client, it is not pushed to the remote server. |
Executable jars can be used for production deployment. As they are self-contained, they are also ideally suited for cloud-based deployment.
For additional “production ready” features, such as health, auditing, and metric REST or JMX end-points, consider adding spring-boot-actuator. See Part V, “Spring Boot Actuator: Production-ready features” for details.
You should now understand how you can use Spring Boot and some best practices that you should follow. You can now go on to learn about specific Spring Boot featuresin depth, or you could skip ahead and read about the “production ready” aspects of Spring Boot.
This section dives into the details of Spring Boot. Here you can learn about the key features that you may want to use and customize. If you have not already done so, you might want to read the "Part II, “Getting Started”" and "Part III, “Using Spring Boot”" sections so that you have a good grounding of the basics.
The SpringApplication class provides a convenient way to bootstrap a Spring application that is started from a main() method. In many situations, you can delegate to the static SpringApplication.run method, as shown in the following example:
public static void main(String[] args) { SpringApplication.run(MySpringConfiguration.class, args); }
When your application starts, you should see something similar to the following output:
. ____ _ __ _ _ /\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \ ( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \ \\/ ___)| |_)| | | | | || (_| | ) ) ) ) ' |____| .__|_| |_|_| |_\__, | / / / / =========|_|==============|___/=/_/_/_/ :: Spring Boot :: v2.0.0.BUILD-SNAPSHOT 2013-07-31 00:08:16.117 INFO 56603 --- [ main] o.s.b.s.app.SampleApplication : Starting SampleApplication v0.1.0 on mycomputer with PID 56603 (/apps/myapp.jar started by pwebb) 2013-07-31 00:08:16.166 INFO 56603 --- [ main] ationConfigServletWebServerApplicationContext : Refreshing org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext@6e5a8246: startup date [Wed Jul 31 00:08:16 PDT 2013]; root of context hierarchy 2014-03-04 13:09:54.912 INFO 41370 --- [ main] .t.TomcatServletWebServerFactory : Server initialized with port: 8080 2014-03-04 13:09:56.501 INFO 41370 --- [ main] o.s.b.s.app.SampleApplication : Started SampleApplication in 2.992 seconds (JVM running for 3.658)
By default, INFO logging messages are shown, including some relevant startup details, such as the user that launched the application.
If your application fails to start, registered FailureAnalyzers get a chance to provide a dedicated error message and a concrete action to fix the problem. For instance, if you start a web application on port 8080 and that port is already in use, you should see something similar to the following message:
*************************** APPLICATION FAILED TO START *************************** Description: Embedded servlet container failed to start. Port 8080 was already in use. Action: Identify and stop the process that's listening on port 8080 or configure this application to listen on another port.
|
| Spring Boot provides numerous |
If no failure analyzers are able to handle the exception, you can still display the full conditions report to better understand what went wrong. To do so, you need to enable the debug property or enable DEBUG logging for org.springframework.boot.autoconfigure.logging.ConditionEvaluationReportLoggingListener.
For instance, if you are running your application by using java -jar, you can enable the debug property as follows:
$ java -jar myproject-0.0.1-SNAPSHOT.jar --debug</boot-features-startup-failure>
The banner that is printed on start up can be changed by adding a banner.txt file to your classpath or by setting the banner.location property to the location of such a file. If the file has an encoding other than UTF-8, you can set banner.charset. In addition to a text file, you can also add a banner.gif, banner.jpg, or banner.png image file to your classpath or set the banner.image.location property. Images are converted into an ASCII art representation and printed above any text banner.
Inside your banner.txt file, you can use any of the following placeholders:
Table 23.1. Banner variables
| Variable | Description |
|---|---|
|
|
The version number of your application, as declared in |
|
|
The version number of your application, as declared in |
|
|
The Spring Boot version that you are using. For example |
|
|
The Spring Boot version that you are using, formatted for display (surrounded with brackets and prefixed with |
|
|
Where |
|
|
The title of your application, as declared in |
|
| The |
You can also use the spring.main.banner-mode property to determine if the banner has to be printed on System.out (console), sent to the configured logger (log), or not produced at all (off).
The printed banner is registered as a singleton bean under the following name: springBootBanner.
|
| YAML maps spring:
main: banner-mode: "off" |
If the SpringApplication defaults are not to your taste, you can instead create a local instance and customize it. For example, to turn off the banner, you could write:
public static void main(String[] args) { SpringApplication app = new SpringApplication(MySpringConfiguration.class); app.setBannerMode(Banner.Mode.OFF); app.run(args); }
|
| The constructor arguments passed to |
It is also possible to configure the SpringApplication by using an application.properties file. See Chapter 24, Externalized Configuration for details.
For a complete list of the configuration options, see the SpringApplication Javadoc.
If you need to build an ApplicationContext hierarchy (multiple contexts with a parent/child relationship) or if you just prefer using a ‘fluent’ builder API, you can use the SpringApplicationBuilder.
The SpringApplicationBuilder lets you chain together multiple method calls and includes parent and child methods that let you create a hierarchy, as shown in the following example:
new SpringApplicationBuilder()
.sources(Parent.class) .child(Application.class) .bannerMode(Banner.Mode.OFF) .run(args);
|
| There are some restrictions when creating an |
In addition to the usual Spring Framework events, such as ContextRefreshedEvent, a SpringApplication sends some additional application events.
|
| Some events are actually triggered before the If you want those listeners to be registered automatically, regardless of the way the application is created, you can add a org.springframework.context.ApplicationListener=com.example.project.MyListener |
Application events are sent in the following order, as your application runs:
- An
ApplicationStartingEventis sent at the start of a run but before any processing except the registration of listeners and initializers. - An
ApplicationEnvironmentPreparedEventis sent when theEnvironmentto be used in the context is known but before the context is created. - An
ApplicationPreparedEventis sent just before the refresh is started but after bean definitions have been loaded. - An
ApplicationReadyEventis sent after the refresh and any related callbacks have been processed, to indicate that the application is ready to service requests. - An
ApplicationFailedEventis sent if there is an exception on startup.
|
| You often need not use application events, but it can be handy to know that they exist. Internally, Spring Boot uses events to handle a variety of tasks. |
Application events are sent by using Spring Framework’s event publishing mechanism. Part of this mechanism ensures that an event published to the listeners in a child context is also published to the listeners in any ancestors contexts. As a result of this, if your application uses a hierarchy of SpringApplication instances, a listener may receive multiple instances of the same type of application event.
To allow your listener to distinguish between an event for its context and an event for a descendant context, it should request that its application context is injected and then compare the injected context with the context of the event. The context can be injected by implementing ApplicationContextAware or, if the listener is a bean, by using @Autowired.
A SpringApplication attempts to create the right type of ApplicationContext on your behalf. By default, an AnnotationConfigApplicationContext orAnnotationConfigServletWebServerApplicationContext is used, depending on whether you are developing a web application or not.
The algorithm used to determine a ‘web environment’ is fairly simplistic (it is based on the presence of a few classes). You can usesetWebEnvironment(boolean webEnvironment) if you need to override the default.
It is also possible to take complete control of the ApplicationContext type that is used by calling setApplicationContextClass(…).
|
| It is often desirable to call |
If you need to access the application arguments that were passed to SpringApplication.run(…), you can inject aorg.springframework.boot.ApplicationArguments bean. The ApplicationArguments interface provides access to both the raw String[] arguments as well as parsed option and non-option arguments, as shown in the following example:
import org.springframework.boot.*
import org.springframework.beans.factory.annotation.* import org.springframework.stereotype.* @Component public class MyBean { @Autowired public MyBean(ApplicationArguments args) { boolean debug = args.containsOption("debug"); List<String> files = args.getNonOptionArgs(); // if run with "--debug logfile.txt" debug=true, files=["logfile.txt"] } }
|
| Spring Boot also registers a |
If you need to run some specific code once the SpringApplication has started, you can implement the ApplicationRunner or CommandLineRunner interfaces. Both interfaces work in the same way and offer a single run method, which is called just before SpringApplication.run(…) completes.
The CommandLineRunner interfaces provides access to application arguments as a simple string array, whereas the ApplicationRunner uses the ApplicationArguments interface discussed earlier.
import org.springframework.boot.*
import org.springframework.stereotype.* @Component public class MyBean implements CommandLineRunner { public void run(String... args) { // Do something... } }
You can additionally implement the org.springframework.core.Ordered interface or use the org.springframework.core.annotation.Order annotation if several CommandLineRunner or ApplicationRunner beans are defined that must be called in a specific order.
Each SpringApplication registers a shutdown hook with the JVM to ensure that the ApplicationContext closes gracefully on exit. All the standard Spring lifecycle callbacks (such as the DisposableBean interface or the @PreDestroy annotation) can be used.
In addition, beans may implement the org.springframework.boot.ExitCodeGenerator interface if they wish to return a specific exit code when SpringApplication.exit() is called. This exit code can then be passed to System.exit() to return it as a status code, as shown in the following example:
@SpringBootApplication public class ExitCodeApplication { @Bean public ExitCodeGenerator exitCodeGenerator() { return () -> 42; } public static void main(String[] args) { System.exit(SpringApplication .exit(SpringApplication.run(ExitCodeApplication.class, args))); } }
Also, the ExitCodeGenerator interface may be implemented by exceptions. When such an exception is encountered, Spring Boot returns the exit code provided by the implemented getExitCode() method.
It is possible to enable admin-related features for the application by specifying the spring.application.admin.enabled property. This exposes theSpringApplicationAdminMXBean on the platform MBeanServer. You could use this feature to administer your Spring Boot application remotely. This feature could also be useful for any service wrapper implementation.
|
| If you want to know on which HTTP port the application is running, get the property with a key of |
![[Caution]](/image/aHR0cHM6Ly9kb2NzLnNwcmluZy5pby9zcHJpbmctYm9vdC9kb2NzL2N1cnJlbnQtU05BUFNIT1QvcmVmZXJlbmNlL2h0bWxzaW5nbGUvaW1hZ2VzL2NhdXRpb24ucG5n.png) |
Caution |
|---|---|
| Take care when enabling this feature, as the MBean exposes a method to shutdown the application. |
Spring Boot lets you externalize your configuration so that you can work with the same application code in different environments. You can use properties files, YAML files, environment variables, and command-line arguments to externalize configuration. Property values can be injected directly into your beans by using the @Valueannotation, accessed through Spring’s Environment abstraction or bound to structured objects through @ConfigurationProperties.
Spring Boot uses a very particular PropertySource order that is designed to allow sensible overriding of values. Properties are considered in the following order:
- Devtools global settings properties on your home directory (
~/.spring-boot-devtools.propertieswhen devtools is active). @TestPropertySourceannotations on your tests.@SpringBootTest#propertiesannotation attribute on your tests.- Command line arguments.
- Properties from
SPRING_APPLICATION_JSON(inline JSON embedded in an environment variable or system property). ServletConfiginit parameters.ServletContextinit parameters.- JNDI attributes from
java:comp/env. - Java System properties (
System.getProperties()). - OS environment variables.
- A
RandomValuePropertySourcethat only has properties inrandom.*. - Profile-specific application properties outside of your packaged jar (
application-{profile}.propertiesand YAML variants). - Profile-specific application properties packaged inside your jar (
application-{profile}.propertiesand YAML variants). - Application properties outside of your packaged jar (
application.propertiesand YAML variants). - Application properties packaged inside your jar (
application.propertiesand YAML variants). @PropertySourceannotations on your@Configurationclasses.- Default properties (specified using
SpringApplication.setDefaultProperties).
To provide a concrete example, suppose you develop a @Component that uses a name property, as shown in the following example:
import org.springframework.stereotype.*
import org.springframework.beans.factory.annotation.* @Component public class MyBean { @Value("${name}") private String name; // ... }
On your application classpath (for example, inside your jar) you can have an application.properties file that provides a sensible default property value for name. When running in a new environment, an application.properties file can be provided outside of your jar that overrides the name. For one-off testing, you can launch with a specific command line switch (for example, java -jar app.jar --name="Spring").
|
| The $ SPRING_APPLICATION_JSON='{"foo":{"bar":"spam"}}' java -jar myapp.jar In the preceding example, you end up with $ java -Dspring.application.json='{"foo":"bar"}' -jar myapp.jar You can also supply the JSON by using a command line argument, as shown in the following example: $ java -jar myapp.jar --spring.application.json='{"foo":"bar"}' You can also supply the JSON as a JNDI variable, as follows: |
The RandomValuePropertySource is useful for injecting random values (for example, into secrets or test cases). It can produce integers, longs, uuids or strings, as shown in the following example:
my.secret=${random.value}
my.number=${random.int} my.bignumber=${random.long} my.uuid=${random.uuid} my.number.less.than.ten=${random.int(10)} my.number.in.range=${random.int[1024,65536]}
The random.int* syntax is OPEN value (,max) CLOSE where the OPEN,CLOSE are any character and value,max are integers. If max is provided, then value is the minimum value and max is the maximum value (exclusive).
By default, SpringApplication converts any command line option arguments (that is, arguments starting with ‘--’, such as --server.port=9000) to a property and add it to the Spring Environment. As mentioned previously, command line properties always take precedence over other property sources.
If you do not want command line properties to be added to the Environment, you can disable them by using SpringApplication.setAddCommandLineProperties(false).
SpringApplication loads properties from application.properties files in the following locations and adds them to the Spring Environment:
- A
/configsubdirectory of the current directory. - The current directory
- A classpath
/configpackage - The classpath root
The list is ordered by precedence (properties defined in locations higher in the list override those defined in lower locations).
|
| You can also use YAML ('.yml') files as an alternative to '.properties'. |
If you do not like application.properties as the configuration file name, you can switch to another file name by specifying a spring.config.name environment property. You can also refer to an explicit location by using the spring.config.location environment property (a comma-separated list of directory locations or file paths). The following example shows how to specify a different file name:
$ java -jar myproject.jar --spring.config.name=myproject
The following example shows how to specify two locations:
$ java -jar myproject.jar --spring.config.location=classpath:/default.properties,classpath:/override.properties
|
|
|
If spring.config.location contains directories (as opposed to files), they should end in / (and, at runtime, be appended with the names generated from spring.config.name before being loaded, including profile-specific file names). Files specified in spring.config.location are used as-is, with no support for profile-specific variants, and are overridden by any profile-specific properties.
Config locations are searched in reverse order. By default, the configured locations are classpath:/,classpath:/config/,file:./,file:./config/. The resulting search order is the following:
file:./config/file:./classpath:/config/classpath:/
When custom config locations are configured using spring.config.location, they replace the default locations. For example, if spring.config.location is configured with the value classpath:/custom-config/,file:./custom-config/, the search order becomes the following:
file:./custom-config/classpath:custom-config/
Alternatively, when custom config locations are configured by using spring.config.addition-location, they are used in addition to the default locations. Additional locations are searched before the default locations. For example, if additional locations of classpath:/custom-config/,file:./custom-config/ are configured, the search order becomes the following:
file:./custom-config/classpath:custom-config/file:./config/file:./classpath:/config/classpath:/
This search ordering lets you specify default values in one configuration file and then selectively override those values in another. You can provide default values for your application in application.properties (or whatever other basename you choose with spring.config.name) in one of the default locations. These default values can then be overriden at runtime with a different file located in one of the custom locations.
|
| If you use environment variables rather than system properties, most operating systems disallow period-separated key names, but you can use underscores instead (for example, |
|
| If your application runs in a container, then JNDI properties (in |
In addition to application.properties files, profile-specific properties can also be defined by using the naming convention application-{profile}.properties. The Environment has a set of default profiles (by default [default]) that are used if no active profiles are set. In other words, if no profiles are explicitly activated, then properties from application-default.properties are loaded.
Profile-specific properties are loaded from the same locations as standard application.properties, with profile-specific files always overriding the non-specific ones, irrespective of whether the profile-specific files are inside or outside your packaged jar.
If several profiles are specified, a last-wins strategy applies. For example, profiles specified by the spring.profiles.active property are added after those configured through the SpringApplication API and therefore take precedence.
|
| If you have specified any files in |
The values in application.properties are filtered through the existing Environment when they are used, so you can refer back to previously defined values (for example, from System properties).
app.name=MyApp
app.description=${app.name} is a Spring Boot application
|
| You can also use this technique to create ‘short’ variants of existing Spring Boot properties. See the Section 73.4, “Use ‘Short’ Command Line Arguments”how-to for details. |
YAML is a superset of JSON and, as such, is a very convenient format for specifying hierarchical configuration data. The SpringApplication class automatically supports YAML as an alternative to properties whenever you have the SnakeYAML library on your classpath.
|
| If you use ‘Starters’, SnakeYAML is automatically provided by |
Spring Framework provides two convenient classes that can be used to load YAML documents. The YamlPropertiesFactoryBean loads YAML as Properties and the YamlMapFactoryBean loads YAML as a Map.
For example, consider the following YAML document:
environments:
dev: url: http://dev.bar.com name: Developer Setup prod: url: http://foo.bar.com name: My Cool App
The preceding example would be transformed into the following properties:
environments.dev.url=http://dev.bar.com
environments.dev.name=Developer Setup environments.prod.url=http://foo.bar.com environments.prod.name=My Cool App
YAML lists are represented as property keys with [index] dereferencers. For example, consider the following YAML:
my:
servers: - dev.bar.com - foo.bar.com
The preceding example would be transformed into these properties:
my.servers[0]=dev.bar.com
my.servers[1]=foo.bar.com
To bind to properties like that by using the Spring DataBinder utilities (which is what @ConfigurationProperties does), you need to have a property in the target bean of type java.util.List (or Set) and you either need to provide a setter or initialize it with a mutable value. For example, the following example binds to the properties shown previously:
@ConfigurationProperties(prefix="my") public class Config { private List<String> servers = new ArrayList<String>(); public List<String> getServers() { return this.servers; } }
|
| When lists are configured in more than one place, overriding works by replacing the entire list. In the preceding example, when |
The YamlPropertySourceLoader class can be used to expose YAML as a PropertySource in the Spring Environment. Doing so lets you use the @Valueannotation with placeholders syntax to access YAML properties.
You can specify multiple profile-specific YAML documents in a single file by using a spring.profiles key to indicate when the document applies, as shown in the following example:
server:
address: 192.168.1.100 --- spring: profiles: development server: address: 127.0.0.1 --- spring: profiles: production server: address: 192.168.1.120
In the preceding example, if the development profile is active, the server.address property is 127.0.0.1. Similarly, if the production profile is active, theserver.address property is 192.168.1.120. If the development and production profiles are not enabled, then the value for the property is 192.168.1.100.
If none are explicitly active when the application context starts, the default profiles are activated . So, in the following YAML, we set a value for security.user.password that is only available in the "default" profile:
server:
port: 8000 --- spring: profiles: default security: user: password: weak
Whereas, in the following example, the password is always set because it is not attached to any profile, and it would have to be explicitly reset in all other profiles as necessary:
server:
port: 8000 security: user: password: weak
Spring profiles designated by using the "spring.profiles" element may optionally be negated by using the ! character. If both negated and non-negated profiles are specified for a single document, at least one non-negated profile must match, and no negated profiles may match.
YAML files cannot be loaded by using the @PropertySource annotation. So, in the case that you need to load values that way, you need to use a properties file.
As we have seen above, any YAML content is ultimately transformed to properties. That process may be counter-intuitive when overriding “list” properties through a profile.
For example, assume a MyPojo object with name and description attributes that are null by default. The following example exposes a list of MyPojo from FooProperties:
@ConfigurationProperties("foo") public class FooProperties { private final List<MyPojo> list = new ArrayList<>(); public List<MyPojo> getList() { return this.list; } }
Consider the following configuration:
foo:
list: - name: my name description: my description --- spring: profiles: dev foo: list: - name: my another name
If the dev profile is not active, FooProperties.list contains one MyPojo entry as defined above. If the dev profile is enabled however, the list still contains only one entry (with a name of “my another name” and a description of null). This configuration does not add a second MyPojo instance to the list, and it does not merge the items.
When a collection is specified in multiple profiles, the one with the highest priority (and only that one) is used:
foo:
list: - name: my name description: my description - name: another name description: another description --- spring: profiles: dev foo: list: - name: my another name
In the preceding example, if the dev profile is active, FooProperties.list contains one MyPojo entry (with a name of “my another name” and a description of null).
Using the @Value("${property}") annotation to inject configuration properties can sometimes be cumbersome, especially if you are working with multiple properties or your data is hierarchical in nature. Spring Boot provides an alternative method of working with properties that lets strongly typed beans govern and validate the configuration of your application, as shown in the following example:
package com.example;
import java.net.InetAddress; import java.util.ArrayList; import java.util.Collections; import java.util.List; import org.springframework.boot.context.properties.ConfigurationProperties; @ConfigurationProperties("foo") public class FooProperties { private boolean enabled; private InetAddress remoteAddress; private final Security security = new Security(); public boolean isEnabled() { ... } public void setEnabled(boolean enabled) { ... } public InetAddress getRemoteAddress() { ... } public void setRemoteAddress(InetAddress remoteAddress) { ... } public Security getSecurity() { ... } public static class Security { private String username; private String password; private List<String> roles = new ArrayList<>(Collections.singleton("USER")); public String getUsername() { ... } public void setUsername(String username) { ... } public String getPassword() { ... } public void setPassword(String password) { ... } public List<String> getRoles() { ... } public void setRoles(List<String> roles) { ... } } }
The preceding POJO defines the following properties:
foo.enabled,falseby default.foo.remote-address, with a type that can be coerced fromString.foo.security.username, with a nested "security" object whose name is determined by the name of the property. In particular, the return type is not used at all there and could have beenSecurityProperties.foo.security.password.foo.security.roles, with a collection ofString.
|
| Getters and setters are usually mandatory, since binding is through standard Java Beans property descriptors, just like in Spring MVC. A setter may be omitted in the following cases:
Some people use Project Lombok to add getters and setters automatically. Make sure that Lombok does not generate any particular constructor for such type, as it is used automatically by the container to instantiate the object. |
|
| See also the differences between |
You also need to list the properties classes to register in the @EnableConfigurationProperties annotation:
@Configuration @EnableConfigurationProperties(FooProperties.class) public class MyConfiguration { }
|
| When the The bean name in the example above is |
Even if the preceding configuration creates a regular bean for FooProperties, we recommend that @ConfigurationProperties only deal with the environment and, in particular, does not inject other beans from the context. Having said that, the @EnableConfigurationProperties annotation is also automatically applied to your project so that any existing bean annotated with @ConfigurationProperties is configured from the Environment. You could shortcut MyConfiguration by making sure FooProperties is already a bean, as shown in the following example:
@Component @ConfigurationProperties(prefix="foo") public class FooProperties { // ... see the preceding example }
This style of configuration works particularly well with the SpringApplication external YAML configuration, as shown in the following example:
# application.yml
foo: remote-address: 192.168.1.1 security: username: foo roles: - USER - ADMIN # additional configuration as required
To work with @ConfigurationProperties beans, you can just inject them in the same way as any other bean, as shown in the following example:
@Service public class MyService { private final FooProperties properties; @Autowired public MyService(FooProperties properties) { this.properties = properties; } //... @PostConstruct public void openConnection() { Server server = new Server(this.properties.getRemoteAddress()); // ... } }
|
| Using |
As well as using @ConfigurationProperties to annotate a class, you can also use it on public @Bean methods. Doing so can be particularly useful when you want to bind properties to third-party components that are outside of your control.
To configure a bean from the Environment properties, add @ConfigurationProperties to its bean registration, as shown in the following example:
@ConfigurationProperties(prefix = "bar") @Bean public BarComponent barComponent() { ... }
Any property defined with the bar prefix is mapped onto that BarComponent bean in a similar manner as the preceding FooProperties example.
Spring Boot uses some relaxed rules for binding Environment properties to @ConfigurationProperties beans, so there does not need to be an exact match between the Environment property name and the bean property name. Common examples where this is useful include dash-separated environment properties (for example, context-path binds to contextPath), and capitalized environment properties (for example, PORT binds to port).
For example, consider the following @ConfigurationProperties class:
@ConfigurationProperties(prefix="person") public class OwnerProperties { private String firstName; public String getFirstName() { return this.firstName; } public void setFirstName(String firstName) { this.firstName = firstName; } }
In the preceding example, the following properties names can all be used:
Table 24.1. relaxed binding
| Property | Note |
|---|---|
|
|
Standard camel case syntax. |
|
|
Kebab case, which is recommended for use in |
|
|
Underscore notation, which is an alternative format for use in |
|
|
Upper case format, which is recommended when using a system environment variables. |
|
| The |
Table 24.2. relaxed binding rules per property source
| Property Source | Simple | List |
|---|---|---|
| Properties Files |
Camel case, kebab case, or underscore notation |
Standard list syntax using |
| YAML Files |
Camel case, kebab case, or underscore notation |
Standard YAML list syntax or comma-separated values |
| Environment Variables |
Upper case format with underscore as the delimiter. |
Numeric values surrounded by underscores, such as |
| System properties |
Camel case, kebab case, or underscore notation |
Standard list syntax using |
|
| We recommend that, when possible, properties are stored in lower-case kebab format, such as |
Spring attempts to coerce the external application properties to the right type when it binds to the @ConfigurationProperties beans. If you need custom type conversion, you can provide a ConversionService bean (with bean named conversionService) or custom property editors (through a CustomEditorConfigurerbean) or custom Converters (with bean definitions annotated as @ConfigurationPropertiesBinding).
|
| As this bean is requested very early during the application lifecycle, make sure to limit the dependencies that your |
Spring Boot attempts to validate @ConfigurationProperties classes whenever they are annotated with Spring’s @Validated annotation. You can use JSR-303 javax.validation constraint annotations directly on your configuration class. To do so, ensure that a compliant JSR-303 implementation is on your classpath and then add constraint annotations to your fields, as shown in the following example:
@ConfigurationProperties(prefix="foo") @Validated public class FooProperties { @NotNull private InetAddress remoteAddress; // ... getters and setters }
In order to validate the values of nested properties, you must annotate the associated field as @Valid to trigger its validation. The following example builds on the preceding FooProperties example:
@ConfigurationProperties(prefix="connection") @Validated public class FooProperties { @NotNull private InetAddress remoteAddress; @Valid private final Security security = new Security(); // ... getters and setters public static class Security { @NotEmpty public String username; // ... getters and setters } }
You can also add a custom Spring Validator by creating a bean definition called configurationPropertiesValidator. The @Bean method should be declared static. The configuration properties validator is created very early in the application’s lifecycle, and declaring the @Bean method as static lets the bean be created without having to instantiate the @Configuration class. Doing so avoids any problems that may be caused by early instantiation. There is a property validation sample that shows how to set things up.
|
| The |
The @Value annotation is a core container feature, and it does not provide the same features as type-safe configuration properties. The following table summarizes the features that are supported by @ConfigurationProperties and @Value:
| Feature | @ConfigurationProperties |
@Value |
|---|---|---|
| Yes |
No |
|
| Yes |
No |
|
|
|
No |
Yes |
If you define a set of configuration keys for your own components, we recommend you to group them in a POJO annotated with @ConfigurationProperties. You should also be aware that, since @Value does not support relaxed binding, it is not a good candidate if you need to provide the value by using environment variables.
Finally, while you can write a SpEL expression in @Value, such expressions are not processed from Application property files.
Spring Profiles provide a way to segregate parts of your application configuration and make it be available only in certain environments. Any @Component or @Configuration can be marked with @Profile to limit when it is loaded, as shown in the following example:
@Configuration @Profile("production") public class ProductionConfiguration { // ... }
In the normal Spring way, you can use a spring.profiles.active Environment property to specify which profiles are active. You can specify the property in any of the usual ways. For example, you could include it in your application.properties:
spring.profiles.active=dev,hsqldb
You could also specify it on the command line by using the following switch: --spring.profiles.active=dev,hsqldb.
The spring.profiles.active property follows the same ordering rules as other properties: The highest PropertySource wins. This means that you can specify active profiles in application.properties and then replace them by using the command line switch.
Sometimes, it is useful to have profile-specific properties that add to the active profiles rather than replace them. The spring.profiles.include property can be used to unconditionally add active profiles. The SpringApplication entry point also has a Java API for setting additional profiles (that is, on top of those activated by thespring.profiles.active property). See the setAdditionalProfiles() method.
For example, when an application with the following properties is run by using the switch, --spring.profiles.active=prod, the proddb and prodmq profiles are also activated:
---
my.property: fromyamlfile --- spring.profiles: prod spring.profiles.include: - proddb - prodmq
|
| Remember that the |
You can programmatically set active profiles by calling SpringApplication.setAdditionalProfiles(…) before your application runs. It is also possible to activate profiles by using Spring’s ConfigurableEnvironment interface.
Profile-specific variants of both application.properties (or application.yml) and files referenced through @ConfigurationProperties are considered as files are loaded. See Section 24.4, “Profile-specific Properties” for details.
Spring Boot uses Commons Logging for all internal logging but leaves the underlying log implementation open. Default configurations are provided for Java Util Logging, Log4J2, and Logback. In each case, loggers are pre-configured to use console output with optional file output also available.
By default, if you use the ‘Starters’, Logback is used for logging. Appropriate Logback routing is also included to ensure that dependent libraries that use Java Util Logging, Commons Logging, Log4J, or SLF4J all work correctly.
|
| There are a lot of logging frameworks available for Java. Do not worry if the above list seems confusing. Generally, you do not need to change your logging dependencies and the Spring Boot defaults work just fine. |
The default log output from Spring Boot resembles the following example:
2014-03-05 10:57:51.112 INFO 45469 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet Engine: Apache Tomcat/7.0.52 2014-03-05 10:57:51.253 INFO 45469 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext 2014-03-05 10:57:51.253 INFO 45469 --- [ost-startStop-1] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 1358 ms 2014-03-05 10:57:51.698 INFO 45469 --- [ost-startStop-1] o.s.b.c.e.ServletRegistrationBean : Mapping servlet: 'dispatcherServlet' to [/] 2014-03-05 10:57:51.702 INFO 45469 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]
The following items are output:
- Date and Time — Millisecond precision and easily sortable.
- Log Level —
ERROR,WARN,INFO,DEBUG, orTRACE. - Process ID.
- A
---separator to distinguish the start of actual log messages. - Thread name — Enclosed in square brackets (may be truncated for console output).
- Logger name — This is usually the source class name (often abbreviated).
- The log message.
|
| Logback does not have a |
The default log configuration echoes messages to the console as they are written. By default, ERROR-level, WARN-level, and INFO-level messages are logged. You can also enable a “debug” mode by starting your application with a --debug flag.
$ java -jar myapp.jar --debug
|
| You can also specify |
When the debug mode is enabled, a selection of core loggers (embedded container, Hibernate, and Spring Boot) are configured to output more information. Enabling the debug mode does not configure your application to log all messages with DEBUG level.
Alternatively, you can enable a “trace” mode by starting your application with a --trace flag (or trace=true in your application.properties). Doing so enables trace logging for a selection of core loggers (embedded container, Hibernate schema generation, and the whole Spring portfolio).
If your terminal supports ANSI, color output is used to aid readability. You can set spring.output.ansi.enabled to a supported value to override the auto detection.
Color coding is configured by using the %clr conversion word. In its simplest form the converter colors the output according to the log level, as shown in the following example:
%clr(%5p)
The mapping of log level to a color is as follows:
| Level | Color |
|---|---|
|
|
Red |
|
|
Red |
|
|
Yellow |
|
|
Green |
|
|
Green |
|
|
Green |
Alternatively, you can specify the color or style that should be used by providing it as an option to the conversion. For example, to make the text yellow, use the following setting:
%clr(%d{yyyy-MM-dd HH:mm:ss.SSS}){yellow}
The following colors and styles are supported:
bluecyanfaintgreenmagentaredyellow
By default, Spring Boot logs only to the console and does not write log files. If you want to write log files in addition to the console output, you need to set alogging.file or logging.path property (for example, in your application.properties).
The following table shows how the logging.* properties can be used together:
Table 26.1. Logging properties
logging.file |
logging.path |
Example | Description |
|---|---|---|---|
| (none) |
(none) |
Console only logging. |
|
| Specific file |
(none) |
|
Writes to the specified log file. Names can be an exact location or relative to the current directory. |
| (none) |
Specific directory |
|
Writes |
Log files rotate when they reach 10 MB and, as with console output, ERROR-level, WARN-level, and INFO-level messages are logged by default. Size limits can be changed using the logging.file.max-size property. Previously rotated files are archived indefinitely unless the logging.file.max-history property has been set.
|
| The logging system is initialized early in the application lifecycle. Consequently, logging properties are not found in property files loaded through |
|
| Logging properties are independent of the actual logging infrastructure. As a result, specific configuration keys (such as |
All the supported logging systems can have the logger levels set in the Spring Environment (for example, in application.properties) by using ‘logging.level.*=LEVEL’ where ‘LEVEL’ is one of TRACE, DEBUG, INFO, WARN, ERROR, FATAL, or OFF. The root logger can be configured by using logging.level.root. The following example shows potential logging settings in application.properties:
logging.level.root=WARN
logging.level.org.springframework.web=DEBUG logging.level.org.hibernate=ERROR
The various logging systems can be activated by including the appropriate libraries on the classpath and can be further customized by providing a suitable configuration file in the root of the classpath or in a location specified by the Spring Environment property logging.config.
You can force Spring Boot to use a particular logging system by using the org.springframework.boot.logging.LoggingSystem system property. The value should be the fully qualified class name of a LoggingSystem implementation. You can also disable Spring Boot’s logging configuration entirely by using a value of none.
|
| Since logging is initialized before the |
Depending on your logging system, the following files are loaded:
| Logging System | Customization |
|---|---|
| Logback |
|
| Log4j2 |
|
| JDK (Java Util Logging) |
|
|
| When possible, we recommend that you use the |
|
| There are known classloading issues with Java Util Logging that cause problems when running from an ‘executable jar’. We recommend that you avoid it when running from an '`executable jar’if at all possible. |
To help with the customization, some other properties are transferred from the Spring Environment to System properties, as described in the following table:
| Spring Environment | System Property | Comments |
|---|---|---|
|
|
|
The conversion word used when logging exceptions. |
|
|
|
If defined, it is used in the default log configuration. |
|
|
|
Maximum log file size (if LOG_FILE enabled). (Only supported with the default logback setup.) |
|
|
|
Maximum number of archive log files to keep (if LOG_FILE enabled). (Only supported with the default logback setup.) |
|
|
|
If defined, it is used in the default log configuration. |
|
|
|
The log pattern to use on the console (stdout). (Only supported with the default logback setup.) |
|
|
|
The log pattern to use in a file (if |
|
|
|
The format to use when rendering the log level (default |
|
|
|
The current process ID (discovered if possible and when not already defined as an OS environment variable). |
All the supported logging systems can consult System properties when parsing their configuration files. See the default configurations in spring-boot.jar for examples:
|
| If you want to use a placeholder in a logging property, you should use Spring Boot’s syntax and not the syntax of the underlying framework. Notably, if you use Logback, you should use |
|
| You can add MDC and other ad-hoc content to log lines by overriding only the 2015-09-30 12:30:04.031 user:someone INFO 22174 --- [ nio-8080-exec-0] demo.Controller Handling authenticated request |
Spring Boot includes a number of extensions to Logback that can help with advanced configuration. You can use these extensions in your logback-spring.xmlconfiguration file.
|
| Because the standard |
|
| The extensions cannot be used with Logback’s configuration scanning. If you attempt to do so, making changes to the configuration file results in an error similar to one of the following being logged: |
ERROR in ch.qos.logback.core.joran.spi.Interpreter@4:71 - no applicable action for [springProperty], current ElementPath is [[configuration][springProperty]] ERROR in ch.qos.logback.core.joran.spi.Interpreter@4:71 - no applicable action for [springProfile], current ElementPath is [[configuration][springProfile]]
The <springProfile> tag lets you optionally include or exclude sections of configuration based on the active Spring profiles. Profile sections are supported anywhere within the <configuration> element. Use the name attribute to specify which profile accepts the configuration. Multiple profiles can be specified using a comma-separated list. The following listing shows three sample profiles:
<springProfile name="staging"> <!-- configuration to be enabled when the "staging" profile is active --> </springProfile> <springProfile name="dev, staging"> <!-- configuration to be enabled when the "dev" or "staging" profiles are active --> </springProfile> <springProfile name="!production"> <!-- configuration to be enabled when the "production" profile is not active --> </springProfile>
The <springProperty> tag lets you expose properties from the Spring Environment for use within Logback. Doing so can be useful if you want to access values from your application.properties file in your Logback configuration. The tag works in a similar way to Logback’s standard <property> tag. However, rather than specifying a direct value, you specify the source of the property (from the Environment). If you need to store the property somewhere other than in local scope, you can use the scope attribute. If you need a fallback value (in case the property is not set in the Environment), you can use the defaultValue attribute.
<springProperty scope="context" name="fluentHost" source="myapp.fluentd.host" defaultValue="localhost"/> <appender name="FLUENT" class="ch.qos.logback.more.appenders.DataFluentAppender"> <remoteHost>${fluentHost}</remoteHost> ... </appender>
|
| The |
Spring Boot is well suited for web application development. You can create a self-contained HTTP server by using embedded Tomcat, Jetty, Undertow, or Netty. Most web applications use the spring-boot-starter-web module to get up and running quickly. You can also choose to build reactive web applications by using thespring-boot-starter-webflux module.
If you have not yet developed a Spring Boot web application, you can follow the "Hello World!" example in the Getting started section.
The Spring Web MVC framework (often referred to as simply ‘Spring MVC’) is a rich ‘model view controller’ web framework. Spring MVC lets you create special @Controller or @RestController beans to handle incoming HTTP requests. Methods in your controller are mapped to HTTP by using @RequestMappingannotations.
The following code shows a typical example @RestController to serve JSON data:
@RestController @RequestMapping(value="/users") public class MyRestController { @RequestMapping(value="/{user}", method=RequestMethod.GET) public User getUser(@PathVariable Long user) { // ... } @RequestMapping(value="/{user}/customers", method=RequestMethod.GET) List<Customer> getUserCustomers(@PathVariable Long user) { // ... } @RequestMapping(value="/{user}", method=RequestMethod.DELETE) public User deleteUser(@PathVariable Long user) { // ... } }
Spring MVC is part of the core Spring Framework, and detailed information is available in the reference documentation. There are also several guides that cover Spring MVC available at spring.io/guides.
Spring Boot provides auto-configuration for Spring MVC that works well with most applications.
The auto-configuration adds the following features on top of Spring’s defaults:
- Inclusion of
ContentNegotiatingViewResolverandBeanNameViewResolverbeans. - Support for serving static resources, including support for WebJars (covered later in this document).
- Automatic registration of
Converter,GenericConverter, andFormatterbeans. - Support for
HttpMessageConverters(see below). - Automatic registration of
MessageCodesResolver(covered later in this document). - Static
index.htmlsupport. - Custom
Faviconsupport (covered later in this document). - Automatic use of a
ConfigurableWebBindingInitializerbean (covered later in this document).
If you want to keep Spring Boot MVC features and you want to add additional MVC configuration (interceptors, formatters, view controllers, and other features), you can add your own @Configuration class of type WebMvcConfigurer but without @EnableWebMvc. If you wish to provide custom instances of RequestMappingHandlerMapping, RequestMappingHandlerAdapter, or ExceptionHandlerExceptionResolver, you can declare a WebMvcRegistrationsAdapter instance to provide such components.
If you want to take complete control of Spring MVC, you can add your own @Configuration annotated with @EnableWebMvc.
Spring MVC uses the HttpMessageConverter interface to convert HTTP requests and responses. Sensible defaults are included out of the box. For example, objects can be automatically converted to JSON (by using the Jackson library) or XML (by using the Jackson XML extension, if available, or by using JAXB if the Jackson XML extension is not available). By default, strings are encoded in UTF-8.
If you need to add or customize converters, you can use Spring Boot’s HttpMessageConverters class:
import org.springframework.boot.autoconfigure.web.HttpMessageConverters;
import org.springframework.context.annotation.*; import org.springframework.http.converter.*; @Configuration public class MyConfiguration { @Bean public HttpMessageConverters customConverters() { HttpMessageConverter<?> additional = ... HttpMessageConverter<?> another = ... return new HttpMessageConverters(additional, another); } }
Any HttpMessageConverter bean that is present in the context is added to the list of converters. You can also override default converters in the same way.
If you use Jackson to serialize and deserialize JSON data, you might want to write your own JsonSerializer and JsonDeserializer classes. Custom serializers are usually registered with Jackson through a module, but Spring Boot provides an alternative @JsonComponent annotation that makes it easier to directly register Spring Beans.
You can use the @JsonComponent annotation directly on JsonSerializer or JsonDeserializer implementations. You can also use it on classes that contains serializers/deserializers as inner-classes, as shown in the following example:
import java.io.*;
import com.fasterxml.jackson.core.*; import com.fasterxml.jackson.databind.*; import org.springframework.boot.jackson.*; @JsonComponent public class Example { public static class Serializer extends JsonSerializer<SomeObject> { // ... } public static class Deserializer extends JsonDeserializer<SomeObject> { // ... } }
All @JsonComponent beans in the ApplicationContext are automatically registered with Jackson. Because @JsonComponent is meta-annotated with @Component, the usual component-scanning rules apply.
Spring Boot also provides JsonObjectSerializer and JsonObjectDeserializer base classes that provide useful alternatives to the standard Jackson versions when serializing objects. See JsonObjectSerializer and JsonObjectDeserializer in the Javadoc for details.
Spring MVC has a strategy for generating error codes for rendering error messages from binding errors: MessageCodesResolver. If you set thespring.mvc.message-codes-resolver.format property PREFIX_ERROR_CODE or POSTFIX_ERROR_CODE, Spring Boot creates one for you (see the enumeration inDefaultMessageCodesResolver.Format).
By default, Spring Boot serves static content from a directory called /static (or /public or /resources or /META-INF/resources) in the classpath or from the root of the ServletContext. It uses the ResourceHttpRequestHandler from Spring MVC so that you can modify that behavior by adding your own WebMvcConfigurerand overriding the addResourceHandlers method.
In a stand-alone web application, the default servlet from the container is also enabled and acts as a fallback, serving content from the root of the ServletContext if Spring decides not to handle it. Most of the time, this will not happen (unless you modify the default MVC configuration) because Spring can always handle requests through the DispatcherServlet.
By default, resources are mapped on /**, but you can tune that with the spring.mvc.static-path-pattern property. For instance, relocating all resources to/resources/** can be achieved as follows:
spring.mvc.static-path-pattern=/resources/**
You can also customize the static resource locations by using the spring.resources.static-locations property (replacing the default values with a list of directory locations). The root Servlet context path "/" is automatically added as a location as well. If you do this, the default welcome page detection switches to your custom locations. So, if there is an index.html in any of your locations on startup, it is the home page of the application.
In addition to the ‘standard’ static resource locations mentioned earlier, a special case is made for Webjars content. Any resources with a path in /webjars/** are served from jar files if they are packaged in the Webjars format.
|
| Do not use the |
Spring Boot also supports the advanced resource handling features provided by Spring MVC, allowing use cases such as cache-busting static resources or using version agnostic URLs for Webjars.
To use version agnostic URLs for Webjars, add the webjars-locator dependency. Then declare your Webjar. Using jQuery as an example, adding"/webjars/jquery/dist/jquery.min.js" results in "/webjars/jquery/x.y.z/dist/jquery.min.js". where x.y.z is the Webjar version.
|
| If you are using JBoss, you need to declare the |
To use cache busting, the following configuration configures a cache busting solution for all static resources, effectively adding a content hash, such as<link href="/css/spring-2a2d595e6ed9a0b24f027f2b63b134d6.css"/>, in URLs:
spring.resources.chain.strategy.content.enabled=true
spring.resources.chain.strategy.content.paths=/**
|
| Links to resources are rewritten in templates at runtime, thanks to a |
When loading resources dynamically with, for example, a JavaScript module loader, renaming files is not an option. That is why other strategies are also supported and can be combined. A "fixed" strategy adds a static version string in the URL without changing the file name, as shown in the following example:
spring.resources.chain.strategy.content.enabled=true
spring.resources.chain.strategy.content.paths=/** spring.resources.chain.strategy.fixed.enabled=true spring.resources.chain.strategy.fixed.paths=/js/lib/ spring.resources.chain.strategy.fixed.version=v12
With this configuration, JavaScript modules located under "/js/lib/" use a fixed versioning strategy ("/v12/js/lib/mymodule.js"), while other resources still use the content one (<link href="/css/spring-2a2d595e6ed9a0b24f027f2b63b134d6.css"/>).
See ResourceProperties for more of the supported options.
|
| This feature has been thoroughly described in a dedicated blog post and in Spring Framework’s reference documentation. |
Spring Boot looks for a favicon.ico in the configured static content locations and the root of the classpath (in that order). If such a file is present, it is automatically used as the favicon of the application.
Spring MVC uses a WebBindingInitializer to initialize a WebDataBinder for a particular request. If you create your own ConfigurableWebBindingInitializer@Bean, Spring Boot automatically configures Spring MVC to use it.
As well as REST web services, you can also use Spring MVC to serve dynamic HTML content. Spring MVC supports a variety of templating technologies, including Thymeleaf, FreeMarker, and JSPs. Also, many other templating engines include their own Spring MVC integrations.
Spring Boot includes auto-configuration support for the following templating engines:
|
| If possible, JSPs should be avoided. There are several known limitations when using them with embedded servlet containers. |
When you use one of these templating engines with the default configuration, your templates are picked up automatically from src/main/resources/templates.
|
| Depending on how you run your application, IntelliJ IDEA orders the classpath differently. Running your application in the IDE from its main method results in a different ordering than when you run your application by using Maven or Gradle or from its packaged jar. This can cause Spring Boot to fail to find the templates on the classpath. If you have this problem, you can reorder the classpath in the IDE to place the module’s classes and resources first. Alternatively, you can configure the template prefix to search every templates directory on the classpath, as follows: |
By default, Spring Boot provides an /error mapping that handles all errors in a sensible way, and it is registered as a ‘global’ error page in the servlet container. For machine clients, it produces a JSON response with details of the error, the HTTP status, and the exception message. For browser clients, there is a ‘whitelabel’ error view that renders the same data in HTML format (to customize it, add a View that resolves to ‘error’). To replace the default behavior completely, you can implementErrorController and register a bean definition of that type or add a bean of type ErrorAttributes to use the existing mechanism but replace the contents.
|
| The |
You can also define a class annotated with @ControllerAdvice to customize the JSON document to return for a particular controller and/or exception type, as shown in the following example:
@ControllerAdvice(basePackageClasses = FooController.class) public class FooControllerAdvice extends ResponseEntityExceptionHandler { @ExceptionHandler(YourException.class) @ResponseBody ResponseEntity<?> handleControllerException(HttpServletRequest request, Throwable ex) { HttpStatus status = getStatus(request); return new ResponseEntity<>(new CustomErrorType(status.value(), ex.getMessage()), status); } private HttpStatus getStatus(HttpServletRequest request) { Integer statusCode = (Integer) request.getAttribute("javax.servlet.error.status_code"); if (statusCode == null) { return HttpStatus.INTERNAL_SERVER_ERROR; } return HttpStatus.valueOf(statusCode); } }
In the preceding example, if YourException is thrown by a controller defined in the same package as FooController, a JSON representation of the CustomErrorType POJO is used instead of the ErrorAttributes representation.
If you want to display a custom HTML error page for a given status code, you can add a file to an /error folder. Error pages can either be static HTML (that is, added under any of the static resource folders) or built by using templates. The name of the file should be the exact status code or a series mask.
For example, to map 404 to a static HTML file, your folder structure would be as follows:
src/
+- main/
+- java/
| + <source code>
+- resources/
+- public/
+- error/
| +- 404.html
+- <other public assets>
To map all 5xx errors by using a FreeMarker template, your folder structure would be as follows:
src/
+- main/
+- java/
| + <source code>
+- resources/
+- templates/
+- error/
| +- 5xx.ftl
+- <other templates>
For more complex mappings, you can also add beans that implement the ErrorViewResolver interface, as shown in the following example:
public class MyErrorViewResolver implements ErrorViewResolver { @Override public ModelAndView resolveErrorView(HttpServletRequest request, HttpStatus status, Map<String, Object> model) { // Use the request or status to optionally return a ModelAndView return ... } }
You can also use regular Spring MVC features such as @ExceptionHandler methods and @ControllerAdvice. The ErrorController then picks up any unhandled exceptions.
For applications that do not use Spring MVC, you can use the ErrorPageRegistrar interface to directly register ErrorPages. This abstraction works directly with the underlying embedded servlet container and works even if you do not have a Spring MVC DispatcherServlet.
@Bean public ErrorPageRegistrar errorPageRegistrar(){ return new MyErrorPageRegistrar(); } // ... private static class MyErrorPageRegistrar implements ErrorPageRegistrar { @Override public void registerErrorPages(ErrorPageRegistry registry) { registry.addErrorPages(new ErrorPage(HttpStatus.BAD_REQUEST, "/400")); } }
|
| If you register an |
@Bean public FilterRegistrationBean myFilter() { FilterRegistrationBean registration = new FilterRegistrationBean(); registration.setFilter(new MyFilter()); ... registration.setDispatcherTypes(EnumSet.allOf(DispatcherType.class)); return registration; }
Note that the default FilterRegistrationBean does not include the ERROR dispatcher type.
When deployed to a servlet container, Spring Boot uses its error page filter to forward a request with an error status to the appropriate error page. The request can only be forwarded to the correct error page if the response has not already been committed. By default, WebSphere Application Server 8.0 and later commits the response upon successful completion of a servlet’s service method. You should disable this behavior by setting com.ibm.ws.webcontainer.invokeFlushAfterService to false.
If you develop a RESTful API that makes use of hypermedia, Spring Boot provides auto-configuration for Spring HATEOAS that works well with most applications. The auto-configuration replaces the need to use @EnableHypermediaSupport and registers a number of beans to ease building hypermedia-based applications, including aLinkDiscoverers (for client side support) and an ObjectMapper configured to correctly marshal responses into the desired representation. The ObjectMapper is customized by setting the various spring.jackson.* properties or, if one exists, by a Jackson2ObjectMapperBuilder bean.
You can take control of Spring HATEOAS’s configuration by using @EnableHypermediaSupport. Note that this disables the ObjectMapper customization described earlier.
Cross-origin resource sharing (CORS) is a W3C specification implemented by most browsers that allows you to specify in a flexible way what kind of cross-domain requests are authorized, instead of using some less secure and less powerful approaches such as IFRAME or JSONP.
As of version 4.2, Spring MVC supports CORS. Using controller method CORS configuration with @CrossOrigin annotations in your Spring Boot application does not require any specific configuration. Global CORS configuration can be defined by registering a WebMvcConfigurer bean with a customizedaddCorsMappings(CorsRegistry) method, as shown in the following example:
@Configuration public class MyConfiguration { @Bean public WebMvcConfigurer corsConfigurer() { return new WebMvcConfigurer() { @Override public void addCorsMappings(CorsRegistry registry) { registry.addMapping("/api/**"); } }; } }
Spring WebFlux is the new reactive web framework introduced in Spring Framework 5.0. Unlike Spring MVC, it does not require the Servlet API, is fully asynchronous and non-blocking, and implements the Reactive Streams specification through the Reactor project.
Spring WebFlux comes in two flavors: functional and annotation-based. The annotation-based one is quite close to the Spring MVC model we know, as shown in the following example:
@RestController @RequestMapping("/users") public class MyRestController { @GetMapping("/{user}") public Mono<User> getUser(@PathVariable Long user) { // ... } @GetMapping("/{user}/customers") Flux<Customer> getUserCustomers(@PathVariable Long user) { // ... } @DeleteMapping("/{user}") public Mono<User> deleteUser(@PathVariable Long user) { // ... } }
‘WebFlux.fn’, the functional variant, separates the routing configuration from the actual handling of the requests, as shown in the following example:
@Configuration public class RoutingConfiguration { @Bean public RouterFunction<ServerResponse> monoRouterFunction(UserHandler userHandler) { return route(GET("/{user}").and(accept(APPLICATION_JSON)), userHandler::getUser) .andRoute(GET("/{user}/customers").and(accept(APPLICATION_JSON)), userHandler::getUserCustomers) .andRoute(DELETE("/{user}").and(accept(APPLICATION_JSON)), userHandler::deleteUser); } } @Component public class UserHandler { public Mono<ServerResponse> getUser(ServerRequest request) { // ... } public Mono<ServerResponse> getUserCustomers(ServerRequest request) { // ... } public Mono<ServerResponse> deleteUser(ServerRequest request) { // ... } }
WebFlux is part of the Spring Framework. and detailed information is available in its reference documentation.
To get started, add the spring-boot-starter-webflux module to your application.
|
| Adding both |
Spring Boot provides auto-configuration for Spring WebFlux that works well with most applications.
The auto-configuration adds the following features on top of Spring’s defaults:
- Configuring codecs for
HttpMessageReaderandHttpMessageWriterinstances (described later in this document). - Support for serving static resources, including support for WebJars (described later in this document).
If you want to keep Spring Boot WebFlux features and you want to add additional WebFlux configuration, you can add your own @Configuration class of type WebFluxConfigurer but without @EnableWebFlux.
If you want to take complete control of Spring WebFlux, you can add your own @Configuration annotated with @EnableWebFlux.
Spring WebFlux uses the HttpMessageReader and HttpMessageWriter interfaces to convert HTTP requests and responses. They are configured with CodecConfigurer to have sensible defaults by looking at the libraries available in your classpath.
Spring Boot applies further customization by using CodecCustomizer instances. For example, spring.jackson.* configuration keys are applied to the Jackson codec.
If you need to add or customize codecs, you can create a custom CodecCustomizer component, as shown in the following example:
import org.springframework.boot.web.codec.CodecCustomizer;
@Configuration
public class MyConfiguration { @Bean public CodecCustomizer myCodecCustomizer() { return codecConfigurer -> { // ... } } }
You can also leverage Boot’s custom JSON serializers and deserializers.
By default, Spring Boot serves static content from a directory called /static (or /public or /resources or /META-INF/resources) in the classpath. It uses theResourceWebHandler from Spring WebFlux so that you can modify that behavior by adding your own WebFluxConfigurer and overriding the addResourceHandlersmethod.
By default, resources are mapped on /**, but you can tune that by setting the spring.webflux.static-path-pattern property. For instance, relocating all resources to /resources/** can be achieved as follows:
spring.webflux.static-path-pattern=/resources/**
You can also customize the static resource locations by using spring.resources.static-locations. Doing so replaces the default values with a list of directory locations. If you do so, the default welcome page detection switches to your custom locations. So, if there is an index.html in any of your locations on startup, it is the home page of the application.
In addition to the ‘standard’ static resource locations listed earlier, a special case is made for Webjars content. Any resources with a path in /webjars/** are served from jar files if they are packaged in the Webjars format.
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| Spring WebFlux applications do not strictly depend on the Servlet API, so they cannot be deployed as war files and do not use the |
As well as REST web services, you can also use Spring WebFlux to serve dynamic HTML content. Spring WebFlux supports a variety of templating technologies, including Thymeleaf, FreeMarker, and Mustache.
Spring Boot includes auto-configuration support for the following templating engines:
When you use one of these templating engines with the default configuration, your templates are picked up automatically from src/main/resources/templates.
Spring Boot provides a WebExceptionHandler that handles all errors in a sensible way. Its position in the processing order is immediately before the handlers provided by WebFlux, which are considered last. For machine clients it will produce a JSON response with details of the error, the HTTP status and the exception message. For browser clients there is a ‘whitelabel’ error handler that renders the same data in HTML format. You can also provide your own HTML templates to display errors (see thenext section).
The first step to customizing this feature is often about using the existing mechanism but replacing or augmenting the error contents. For that, you can simply add a bean of type ErrorAttributes.
To change the error handling behavior, you can implement ErrorWebExceptionHandler and register a bean definition of that type. Because a WebExceptionHandleris quite low-level, Spring Boot also provides a convenient AbstractErrorWebExceptionHandler to let you handle errors in a WebFlux functional way, as shown in the following example:
public class CustomErrorWebExceptionHandler extends AbstractErrorWebExceptionHandler { // Define constructor here @Override protected RouterFunction<ServerResponse> getRoutingFunction(ErrorAttributes errorAttributes) { return RouterFunctions .route(aPredicate, aHandler) .andRoute(anotherPredicate, anotherHandler); } }
For a more complete picture, you can also subclass DefaultErrorWebExceptionHandler directly and override specific methods.
If you want to display a custom HTML error page for a given status code, you can add a file to an /error folder. Error pages can either be static HTML (that is, added under any of the static resource folders) or built with templates. The name of the file should be the exact status code or a series mask.
For example, to map 404 to a static HTML file, your folder structure would be as follows:
src/
+- main/
+- java/
| + <source code>
+- resources/
+- public/
+- error/
| +- 404.html
+- <other public assets>
To map all 5xx errors by using a Mustache template, your folder structure would be as follows:
src/
+- main/
+- java/
| + <source code>
+- resources/
+- templates/
+- error/
| +- 5xx.mustache
+- <other templates>
If you prefer the JAX-RS programming model for REST endpoints, you can use one of the available implementations instead of Spring MVC. Jersey 1.x and Apache CXF work quite well out of the box if you register their Servlet or Filter as a @Bean in your application context. Jersey 2.x has some native Spring support, so we also provide auto-configuration support for it in Spring Boot, together with a starter.
To get started with Jersey 2.x, include the spring-boot-starter-jersey as a dependency and then you need one @Bean of type ResourceConfig in which you register all the endpoints, as shown in the following example:
@Component public class JerseyConfig extends ResourceConfig { public JerseyConfig() { register(Endpoint.class); } }
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| Jersey’s support for scanning executable archives is rather limited. For example, it cannot scan for endpoints in a package found in |
You can also register an arbitrary number of beans implementing ResourceConfigCustomizer for more advanced customizations.
All the registered endpoints should be @Components with HTTP resource annotations (@GET etc.), as shown in the following example:
@Component @Path("/hello") public class Endpoint { @GET public String message() { return "Hello"; } }
Since the Endpoint is a Spring @Component, its lifecycle is managed by Spring and you can use the @Autowired annotation to inject dependencies and use the @Value annotation to inject external configuration. By default, the Jersey servlet is registered and mapped to /*. You can change the mapping by adding @ApplicationPath to your ResourceConfig.
By default, Jersey is set up as a Servlet in a @Bean of type ServletRegistrationBean named jerseyServletRegistration. By default, the servlet is initialized lazily, but you can customize that behavior by setting spring.jersey.servlet.load-on-startup. You can disable or override that bean by creating one of your own with the same name. You can also use a filter instead of a servlet by setting spring.jersey.type=filter (in which case, the @Bean to replace or override is jerseyFilterRegistration). The filter has an @Order, which you can set with spring.jersey.filter.order. Both the servlet and the filter registrations can be given init parameters by using spring.jersey.init.* to specify a map of properties.
There is a Jersey sample so that you can see how to set things up. There is also a Jersey 1.x sample. Note that, in the Jersey 1.x sample, the spring-boot maven plugin has been configured to unpack some Jersey jars so that they can be scanned by the JAX-RS implementation (because the sample asks for them to be scanned in its Filter registration). If any of your JAX-RS resources are packaged as nested jars, you may need to do the same.
Spring Boot includes support for embedded Tomcat, Jetty, and Undertow servers. Most developers use the appropriate ‘Starter’ to obtain a fully configured instance. By default, the embedded server listens for HTTP requests on port 8080.
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| If you choose to use Tomcat on CentOS, be aware that, by default, a temporary directory is used to store compiled JSPs, file uploads, and so on. This directory may be deleted by |
When using an embedded servlet container, you can register servlets, filters, and all the listeners (such as HttpSessionListener) from the Servlet spec, either by using Spring beans or by scanning for Servlet components.
Any Servlet, Filter, or servlet *Listener instance that is a Spring bean is registered with the embedded container. This can be particularly convenient if you want to refer to a value from your application.properties during configuration.
By default, if the context contains only a single Servlet, it is mapped to /. In the case of multiple servlet beans, the bean name is used as a path prefix. Filters map to/*.
If convention-based mapping is not flexible enough, you can use the ServletRegistrationBean, FilterRegistrationBean, andServletListenerRegistrationBean classes for complete control.
Embedded servlet containers do not directly execute the Servlet 3.0+ javax.servlet.ServletContainerInitializer interface or Spring’sorg.springframework.web.WebApplicationInitializer interface. This is an intentional design decision intended to reduce the risk that third party libraries designed to run inside a war may break Spring Boot applications.
If you need to perform servlet context initialization in a Spring Boot application, you should register a bean that implements theorg.springframework.boot.web.servlet.ServletContextInitializer interface. The single onStartup method provides access to the ServletContext and, if necessary, can easily be used as an adapter to an existing WebApplicationInitializer.
When using an embedded container, automatic registration of @WebServlet, @WebFilter, and @WebListener annotated classes can be enabled by using @ServletComponentScan.
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Under the hood, Spring Boot uses a new type of ApplicationContext for embedded servlet container support. The ServletWebServerApplicationContext is a special type of WebApplicationContext that bootstraps itself by searching for a single ServletWebServerFactory bean. Usually a TomcatServletWebServerFactory, JettyServletWebServerFactory, or UndertowServletWebServerFactory has been auto-configured.
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| You usually do not need to be aware of these implementation classes. Most applications are auto-configured, and the appropriate |
Common servlet container settings can be configured by using Spring Environment properties. Usually, you would define the properties in your application.properties file.
Common server settings include:
- Network settings: Listen port for incoming HTTP requests (
server.port), interface address to bind toserver.address, and so on. - Session settings: Whether the session is persistent (
server.session.persistence), session timeout (server.session.timeout), location of session data (server.session.store-dir), and session-cookie configuration (server.session.cookie.*). - Error management: Location of the error page (
server.error.path), and so on. - SSL
- HTTP compression
Spring Boot tries as much as possible to expose common settings, but this is not always possible. For those cases, dedicated namespaces offer server-specific customizations (see server.tomcat and server.undertow). For instance, access logs can be configured with specific features of the embedded servlet container.
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| See the |
If you need to programmatically configure your embedded servlet container, you can register a Spring bean that implements the WebServerFactoryCustomizerinterface. WebServerFactoryCustomizer provides access to the ConfigurableServletWebServerFactory, which includes numerous customization setter methods. Dedicated variants exist for Tomcat, Jetty, and Undertow. The following example shows programmatically setting the port:
import org.springframework.boot.web.server.WebServerFactoryCustomizer;
import org.springframework.boot.web.servlet.server.ConfigurableServletWebServerFactory; import org.springframework.stereotype.Component; @Component public class CustomizationBean implements WebServerFactoryCustomizer<ConfigurableServletWebServerFactory> { @Override public void customize(ConfigurableServletWebServerFactory server) { server.setPort(9000); } }
If the preceding customization techniques are too limited, you can register the TomcatServletWebServerFactory, JettyServletWebServerFactory, orUndertowServletWebServerFactory bean yourself.
@Bean public ConfigurableServletWebServerFactory webServerFactory() { TomcatServletWebServerFactory factory = new TomcatServletWebServerFactory(); factory.setPort(9000); factory.setSessionTimeout(10, TimeUnit.MINUTES); factory.addErrorPages(new ErrorPage(HttpStatus.NOT_FOUND, "/notfound.html")); return factory; }
Setters are provided for many configuration options. Several protected method “hooks” are also provided should you need to do something more exotic. See the source code documentation for details.
When running a Spring Boot application that uses an embedded servlet container (and is packaged as an executable archive), there are some limitations in the JSP support.
- With Tomcat, it should work if you use war packaging. That is, an executable war works and is also deployable to a standard container (not limited to, but including Tomcat). An executable jar does not work because of a hard-coded file pattern in Tomcat.
- With Jetty, it should work if you use war packaging. That is, an executable war works, and is also deployable to any standard container.
- Undertow does not support JSPs.
- Creating a custom
error.jsppage does not override the default view for error handling. Custom error pages should be used instead.
There is a JSP sample so that you can see how to set things up.
If Spring Security is on the classpath, then web applications are secure by default. Spring Boot relies on Spring Security’s content-negotiation strategy to determine whether to use httpBasic or formLogin. To add method-level security to a web application, you can also add @EnableGlobalMethodSecurity with your desired settings. Additional information can be found in the Spring Security Reference.
The default AuthenticationManager has a single user (the user name is ‘user’, and the password is random and is printed at INFO level when the application starts), as shown in the following example:
Using default security password: 78fa095d-3f4c-48b1-ad50-e24c31d5cf35
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| If you fine-tune your logging configuration, ensure that the |
The default security configuration is implemented in SecurityAutoConfiguration and in the classes imported from there (SpringBootWebSecurityConfigurationfor web security and AuthenticationManagerConfiguration for authentication configuration, which is also relevant in non-web applications). To switch off the default web application security configuration completely, you can add a bean of type WebSecurityConfigurerAdapter (this does not disable the authentication manager configuration or Actuator’s security).
To also switch off the authentication manager configuration, you can add a bean of type UserDetailsService, AuthenticationProvider or AuthenticationManager. There are several secure applications in the Spring Boot samples to get you started with common use cases.
The basic features you get by default in a web application are:
- A
UserDetailsServicebean with in-memory store and a single user with a generated password. - Form-based login or HTTP Basic security (depending on Content-Type) for the entire application (including actuator endpoints if actuator is on the classpath).
Access rules can be overriden by adding a custom WebSecurityConfigurerAdapter. Spring Boot provides convenience methods that can be used to override access rules for actuator endpoints and static resources. EndpointRequest can be used to create a RequestMatcher that is based on the management.endpoints.web.base-path property. StaticResourceRequest can be used to create a RequestMatcher for static resources in commonly used locations.
OAuth2 is a widely used authorization framework that is supported by Spring.
If you have spring-security-oauth2-client on your classpath, you can take advantage of some auto-configuration to make it easy to set up an OAuth2 Client. This configuration makes use of the properties under OAuth2ClientProperties.
You can register multiple OAuth2 clients and providers under the spring.security.oauth2.client prefix, as shown in the following example:
spring.security.oauth2.client.registration.my-client-1.client-id=abcd
spring.security.oauth2.client.registration.my-client-1.client-secret=password spring.security.oauth2.client.registration.my-client-1.client-name=Client for user scope spring.security.oauth2.client.registration.my-client-1.provider=my-oauth-provider spring.security.oauth2.client.registration.my-client-1.scope=user spring.security.oauth2.client.registration.my-client-1.redirect-uri-template=http://my-redirect-uri.com spring.security.oauth2.client.registration.my-client-1.client-authentication-method=basic spring.security.oauth2.client.registration.my-client-1.authorization-grant-type=authorization_code spring.security.oauth2.client.registration.my-client-2.client-id=abcd spring.security.oauth2.client.registration.my-client-2.client-secret=password spring.security.oauth2.client.registration.my-client-2.client-name=Client for email scope spring.security.oauth2.client.registration.my-client-2.provider=my-oauth-provider spring.security.oauth2.client.registration.my-client-2.scope=email spring.security.oauth2.client.registration.my-client-2.redirect-uri-template=http://my-redirect-uri.com spring.security.oauth2.client.registration.my-client-2.client-authentication-method=basic spring.security.oauth2.client.registration.my-client-2.authorization-grant-type=authorization_code spring.security.oauth2.client.provider.my-oauth-provider.authorization-uri=http://my-auth-server/oauth/authorize spring.security.oauth2.client.provider.my-oauth-provider.token-uri=http://my-auth-server/oauth/token spring.security.oauth2.client.provider.my-oauth-provider.user-info-uri=http://my-auth-server/userinfo spring.security.oauth2.client.provider.my-oauth-provider.jwk-set-uri=http://my-auth-server/token_keys spring.security.oauth2.client.provider.my-oauth-provider.user-name-attribute=name
By default, Spring Security’s OAuth2LoginAuthenticationFilter will only process URLs matching /login/oauth2/code/*. If you want to customize the redirect-uri-template to use a different pattern, you will need to provide configuration to process that custom pattern. For example, you can add your ownWebSecurityConfigurerAdapter that looks like this:
public class OAuth2LoginSecurityConfig extends WebSecurityConfigurerAdapter { @Override protected void configure(HttpSecurity http) throws Exception { http .authorizeRequests() .anyRequest().authenticated() .and() .oauth2Login() .redirectionEndpoint() .baseUri("/custom-callback"); } }
For common OAuth2 and OpenID providers such as Google, Github, Facebook, and Okta, we provide a set of provider defaults (google, github, facebook, and okta respectively).
If you do not need to customize these providers, you can set the provider attribute to the one for which you need to infer defaults. Also if the ID of your client matches the default supported provider, Spring Boot infers that as well.
In other words, the two configurations in the following example use the Google provider:
spring.security.oauth2.client.registration.my-client.client-id=abcd
spring.security.oauth2.client.registration.my-client.client-secret=password spring.security.oauth2.client.registration.my-client.provider=google spring.security.oauth2.client.registration.google.client-id=abcd spring.security.oauth2.client.registration.google.client-secret=password
If the Actuator is also in use, you can see that:
- The management endpoints are secure even if the application endpoints are insecure.
- Security events are transformed into
AuditEventinstances and published to theAuditEventRepository. - The default user has the
ACTUATORrole as well as theUSERrole.
The Actuator security features can be modified by using external properties (management.security.*). To override the application access rules but not the actuator access rules, add a @Bean of type WebSecurityConfigurerAdapter and use @Order(SecurityProperties.ACCESS_OVERRIDE_ORDER). Use@Order(ManagementServerProperties.ACCESS_OVERRIDE_ORDER) if you do want to override the application access rules and the actuator access rules.
The Spring Framework provides extensive support for working with SQL databases, from direct JDBC access using JdbcTemplate to complete ‘object relational mapping’ technologies such as Hibernate. Spring Data provides an additional level of functionality: creating Repository implementations directly from interfaces and using conventions to generate queries from your method names.
Java’s javax.sql.DataSource interface provides a standard method of working with database connections. Traditionally, a DataSource uses a URL along with some credentials to establish a database connection.
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| See the ‘How-to’ section for more advanced examples, typically to take full control over the configuration of the DataSource. |
It is often convenient to develop applications using an in-memory embedded database. Obviously, in-memory databases do not provide persistent storage. You need to populate your database when your application starts and be prepared to throw away data when your application ends.
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| The ‘How-to’ section includes a section on how to initialize a database. |
Spring Boot can auto-configure embedded H2, HSQL, and Derby databases. You need not provide any connection URLs. You need only include a build dependency to the embedded database that you want to use.
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| If you are using this feature in your tests, you may notice that the same database is reused by your whole test suite regardless of the number of application contexts that you use. If you want to make sure that each context has a separate embedded database, you should set |
For example, typical POM dependencies would be as follows:
<dependency>
<groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-jpa</artifactId> </dependency> <dependency> <groupId>org.hsqldb</groupId> <artifactId>hsqldb</artifactId> <scope>runtime</scope> </dependency>
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| You need a dependency on |
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| If, for whatever reason, you do configure the connection URL for an embedded database, take care to ensure that the database’s automatic shutdown is disabled. If you use H2, you should use |
Production database connections can also be auto-configured by using a pooling DataSource. Spring Boot uses the following algorithm for choosing a specific implementation:
- We prefer HikariCP for its performance and concurrency. If HikariCP is available, we always choose it.
- Otherwise, if the Tomcat pooling
DataSourceis available, we use it. - If neither HikariCP nor the Tomcat pooling datasource are available and if Commons DBCP2 is available, we use it.
If you use the spring-boot-starter-jdbc or spring-boot-starter-data-jpa ‘starters’, you automatically get a dependency to HikariCP.
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| You can bypass that algorithm completely and specify the connection pool to use by setting the |
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| Additional connection pools can always be configured manually. If you define your own |
DataSource configuration is controlled by external configuration properties in spring.datasource.*. For example, you might declare the following section inapplication.properties:
spring.datasource.url=jdbc:mysql://localhost/test
spring.datasource.username=dbuser spring.datasource.password=dbpass spring.datasource.driver-class-name=com.mysql.jdbc.Driver
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| You should at least specify the URL by setting the |
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| You often do not need to specify the |
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| For a pooling |
See DataSourceProperties for more of the supported options. These are the standard options that work regardless of the actual implementation. It is also possible to fine-tune implementation-specific settings using their respective prefix (spring.datasource.hikari.*, spring.datasource.tomcat.*, and spring.datasource.dbcp2.*). Refer to the documentation of the connection pool implementation you are using for more details.
For instance, if you use the Tomcat connection pool, you could customize many additional settings:
# Number of ms to wait before throwing an exception if no connection is available.
spring.datasource.tomcat.max-wait=10000 # Maximum number of active connections that can be allocated from this pool at the same time. spring.datasource.tomcat.max-active=50 # Validate the connection before borrowing it from the pool. spring.datasource.tomcat.test-on-borrow=true
If you deploy your Spring Boot application to an Application Server, you might want to configure and manage your DataSource using your Application Server’s built-in features and access it by using JNDI.
The spring.datasource.jndi-name property can be used as an alternative to the spring.datasource.url, spring.datasource.username, and spring.datasource.password properties to access the DataSource from a specific JNDI location. For example, the following section in application.propertiesshows how you can access a JBoss AS defined DataSource:
spring.datasource.jndi-name=java:jboss/datasources/customers
Spring’s JdbcTemplate and NamedParameterJdbcTemplate classes are auto-configured, and you can @Autowire them directly into your own beans, as shown in the following example:
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate; import org.springframework.stereotype.Component; @Component public class MyBean { private final JdbcTemplate jdbcTemplate; @Autowired public MyBean(JdbcTemplate jdbcTemplate) { this.jdbcTemplate = jdbcTemplate; } // ... }
You can customize some properties of the template by using the spring.jdbc.template.* properties as shown in the following example:
spring.jdbc.template.max-rows=500
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| The |
The Java Persistence API is a standard technology that lets you ‘map’ objects to relational databases. The spring-boot-starter-data-jpa POM provides a quick way to get started. It provides the following key dependencies:
- Hibernate — One of the most popular JPA implementations.
- Spring Data JPA — Makes it easy to implement JPA-based repositories.
- Spring ORMs — Core ORM support from the Spring Framework.
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| We do not go into too many details of JPA or Spring Data here. You can follow the ‘Accessing Data with JPA’ guide from spring.io and read the Spring Data JPA and Hibernate reference documentation. |
Traditionally, JPA ‘Entity’ classes are specified in a persistence.xml file. With Spring Boot, this file is not necessary and ‘Entity Scanning’ is used instead. By default, all packages below your main configuration class (the one annotated with @EnableAutoConfiguration or @SpringBootApplication) are searched.
Any classes annotated with @Entity, @Embeddable or @MappedSuperclass are considered. A typical entity class resembles the following example:
package com.example.myapp.domain;
import java.io.Serializable; import javax.persistence.*; @Entity public class City implements Serializable { @Id @GeneratedValue private Long id; @Column(nullable = false) private String name; @Column(nullable = false) private String state; // ... additional members, often include @OneToMany mappings protected City() { // no-args constructor required by JPA spec // this one is protected since it shouldn't be used directly } public City(String name, String state) { this.name = name; this.country = country; } public String getName() { return this.name; } public String getState() { return this.state; } // ... etc }
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| You can customize entity scanning locations by using the |
Spring Data JPA repositories are interfaces that you can define to access data. JPA queries are created automatically from your method names. For example, a CityRepository interface might declare a findAllByState(String state) method to find all the cities in a given state.
For more complex queries, you can annotate your method with Spring Data’s Query annotation.
Spring Data repositories usually extend from the Repository or CrudRepository interfaces. If you use auto-configuration, repositories are searched from the package containing your main configuration class (the one annotated with @EnableAutoConfiguration or @SpringBootApplication) down.
The following example shows a typical Spring Data repository interface definition:
package com.example.myapp.domain;
import org.springframework.data.domain.*; import org.springframework.data.repository.*; public interface CityRepository extends Repository<City, Long> { Page<City> findAll(Pageable pageable); City findByNameAndCountryAllIgnoringCase(String name, String country); }
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| We have barely scratched the surface of Spring Data JPA. For complete details, see the Spring Data JPA reference documentation. |
By default, JPA databases are automatically created only if you use an embedded database (H2, HSQL, or Derby). You can explicitly configure JPA settings by usingspring.jpa.* properties. For example, to create and drop tables you can add the following line to your application.properties:
spring.jpa.hibernate.ddl-auto=create-drop
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| Hibernate’s own internal property name for this (if you happen to remember it better) is |
spring.jpa.properties.hibernate.globally_quoted_identifiers=true
The line in the preceding example passes a value of true for the hibernate.globally_quoted_identifiers property to the Hibernate entity manager.
By default, the DDL execution (or validation) is deferred until the ApplicationContext has started. There is also a spring.jpa.generate-ddl flag, but it is not used if Hibernate auto-configuration is active, because the ddl-auto settings are more fine-grained.
If you are running a web application, Spring Boot by default registers OpenEntityManagerInViewInterceptor to apply the "Open EntityManager in View" pattern, to allow for lazy loading in web views. If you do not want this behavior, you should set spring.jpa.open-in-view to false in your application.properties.
The H2 database provides a browser-based console that Spring Boot can auto-configure for you. The console is auto-configured when the following conditions are met:
- You are developing a web application.
com.h2database:h2is on the classpath.- You are using Spring Boot’s developer tools.
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| If you are not using Spring Boot’s developer tools but would still like to make use of H2’s console, you can configure the |
Java Object Oriented Querying (jOOQ) is a popular product from Data Geekery which generates Java code from your database and lets you build type-safe SQL queries through its fluent API. Both the commercial and open source editions can be used with Spring Boot.
In order to use jOOQ type-safe queries, you need to generate Java classes from your database schema. You can follow the instructions in the jOOQ user manual. If you use the jooq-codegen-maven plugin and you also use the spring-boot-starter-parent “parent POM”, you can safely omit the plugin’s <version> tag. You can also use Spring Boot-defined version variables (such as h2.version) to declare the plugin’s database dependency. The following listing shows an example:
<plugin>
<groupId>org.jooq</groupId> <artifactId>jooq-codegen-maven</artifactId> <executions> ... </executions> <dependencies> <dependency> <groupId>com.h2database</groupId> <artifactId>h2</artifactId> <version>${h2.version}</version> </dependency> </dependencies> <configuration> <jdbc> <driver>org.h2.Driver</driver> <url>jdbc:h2:~/yourdatabase</url> </jdbc> <generator> ... </generator> </configuration> </plugin>
The fluent API offered by jOOQ is initiated through the org.jooq.DSLContext interface. Spring Boot auto-configures a DSLContext as a Spring Bean and connects it to your application DataSource. To use the DSLContext, you can @Autowire it, as shown in the following example:
@Component public class JooqExample implements CommandLineRunner { private final DSLContext create; @Autowired public JooqExample(DSLContext dslContext) { this.create = dslContext; } }
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| The jOOQ manual tends to use a variable named |
You can then use the DSLContext to construct your queries, as shown in the following example:
public List<GregorianCalendar> authorsBornAfter1980() {
return this.create.selectFrom(AUTHOR) .where(AUTHOR.DATE_OF_BIRTH.greaterThan(new GregorianCalendar(1980, 0, 1))) .fetch(AUTHOR.DATE_OF_BIRTH); }
Unless the spring.jooq.sql-dialect property has been configured, Spring Boot determines the SQL dialect to use for your datasource. If Spring Boot could not detect the dialect, it uses DEFAULT.
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| Spring Boot can only auto-configure dialects supported by the open source version of jOOQ. |
More advanced customizations can be achieved by defining your own @Bean definitions, which will be used when the jOOQ Configuration is created. You can define beans for the following jOOQ Types:
ConnectionProviderTransactionProviderRecordMapperProviderRecordListenerProviderExecuteListenerProviderVisitListenerProvider
You can also create your own org.jooq.Configuration @Bean if you want to take complete control of the jOOQ configuration.
Spring Data provides additional projects that help you access a variety of NoSQL technologies, including: MongoDB, Neo4J, Elasticsearch, Solr, Redis, Gemfire,Cassandra, Couchbase and LDAP. Spring Boot provides auto-configuration for Redis, MongoDB, Neo4j, Elasticsearch, Solr Cassandra, Couchbase, and LDAP. You can make use of the other projects, but you must configure them yourself. Refer to the appropriate reference documentation at projects.spring.io/spring-data.
Redis is a cache, message broker, and richly-featured key-value store. Spring Boot offers basic auto-configuration for the Lettuce and Jedis client libraries and the abstractions on top of them provided by Spring Data Redis.
There is a spring-boot-starter-data-redis ‘Starter’ for collecting the dependencies in a convenient way. By default, it uses Lettuce. That starter handles both traditional and reactive applications.
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| we also provide a |
You can inject an auto-configured RedisConnectionFactory, StringRedisTemplate, or vanilla RedisTemplate instance as you would any other Spring Bean. By default, the instance tries to connect to a Redis server at localhost:6379. The following listing shows an example of such a bean:
@Component public class MyBean { private StringRedisTemplate template; @Autowired public MyBean(StringRedisTemplate template) { this.template = template; } // ... }
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| You can also register an arbitrary number of beans that implement |
If you add your own @Bean of any of the auto-configured types, it replaces the default (except in the case of RedisTemplate, when the exclusion is based on the bean name ‘redisTemplate’, not its type). By default, if commons-pool2 is on the classpath, you get a pooled connection factory.
MongoDB is an open-source NoSQL document database that uses a JSON-like schema instead of traditional table-based relational data. Spring Boot offers several conveniences for working with MongoDB, including the spring-boot-starter-data-mongodb and spring-boot-starter-data-mongodb-reactive ‘Starters’.
To access Mongo databases, you can inject an auto-configured org.springframework.data.mongodb.MongoDbFactory. By default, the instance tries to connect to a MongoDB server at mongodb://localhost/test The following example shows how to connect to a MongoDB database:
import org.springframework.data.mongodb.MongoDbFactory;
import com.mongodb.DB; @Component public class MyBean { private final MongoDbFactory mongo; @Autowired public MyBean(MongoDbFactory mongo) { this.mongo = mongo; } // ... public void example() { DB db = mongo.getDb(); // ... } }
You can set the spring.data.mongodb.uri property to change the URL and configure additional settings such as the replica set, as shown in the following example:
spring.data.mongodb.uri=mongodb://user:secret@mongo1.example.com:12345,mongo2.example.com:23456/test
Alternatively, as long as you use Mongo 2.x, you can specify a host/port. For example, you might declare the following settings in your application.properties:
spring.data.mongodb.host=mongoserver
spring.data.mongodb.port=27017
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| If you use the Mongo 3.0 Java driver, |
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| If |
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| If you do not use Spring Data Mongo, you can inject |
Spring Data Mongo provides a MongoTemplate class that is very similar in its design to Spring’s JdbcTemplate. As with JdbcTemplate, Spring Boot auto-configures a bean for you to inject the template, as follows:
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.mongodb.core.MongoTemplate; import org.springframework.stereotype.Component; @Component public class MyBean { private final MongoTemplate mongoTemplate; @Autowired public MyBean(MongoTemplate mongoTemplate) { this.mongoTemplate = mongoTemplate; } // ... }
See the MongoOperations Javadoc for complete details.
Spring Data includes repository support for MongoDB. As with the JPA repositories discussed earlier, the basic principle is that queries are constructed automatically based on method names.
In fact, both Spring Data JPA and Spring Data MongoDB share the same common infrastructure. You could take the JPA example from earlier and, assuming that Cityis now a Mongo data class rather than a JPA @Entity, it works in the same way, as shown in the following example:
package com.example.myapp.domain;
import org.springframework.data.domain.*; import org.springframework.data.repository.*; public interface CityRepository extends Repository<City, Long> { Page<City> findAll(Pageable pageable); City findByNameAndCountryAllIgnoringCase(String name, String country); }
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| You can customize document scanning locations using the |
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| For complete details of Spring Data MongoDB, including its rich object mapping technologies, refer to the reference documentation. |
Spring Boot offers auto-configuration for Embedded Mongo. To use it in your Spring Boot application, add a dependency onde.flapdoodle.embed:de.flapdoodle.embed.mongo.
The port that Mongo listens on can be configured by setting the spring.data.mongodb.port property. To use a randomly allocated free port, use a value of 0. The MongoClient created by MongoAutoConfiguration is automatically configured to use the randomly allocated port.
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| If you do not configure a custom port, the embedded support uses a random port (rather than 27017) by default. |
If you have SLF4J on the classpath, the output produced by Mongo is automatically routed to a logger named org.springframework.boot.autoconfigure.mongo.embedded.EmbeddedMongo.
You can declare your own IMongodConfig and IRuntimeConfig beans to take control of the Mongo instance’s configuration and logging routing.
Neo4j is an open-source NoSQL graph database that uses a rich data model of nodes related by first class relationships, which is better suited for connected big data than traditional rdbms approaches. Spring Boot offers several conveniences for working with Neo4j, including the spring-boot-starter-data-neo4j ‘Starter’.
You can inject an auto-configured Neo4jSession, Session, or Neo4jOperations instance as you would any other Spring Bean. By default, the instance tries to connect to a Neo4j server at localhost:7474. The following example shows how to inject a Neo4j bean:
@Component public class MyBean { private final Neo4jTemplate neo4jTemplate; @Autowired public MyBean(Neo4jTemplate neo4jTemplate) { this.neo4jTemplate = neo4jTemplate; } // ... }
You can take full control of the configuration by adding a org.neo4j.ogm.config.Configuration @Bean of your own. Also, adding a @Bean of typeNeo4jOperations disables the auto-configuration.
You can configure the user and credentials to use by setting the spring.data.neo4j.* properties, as shown in the following example:
spring.data.neo4j.uri=http://my-server:7474
spring.data.neo4j.username=neo4j spring.data.neo4j.password=secret
If you add org.neo4j:neo4j-ogm-embedded-driver to the dependencies of your application, Spring Boot automatically configures an in-process embedded instance of Neo4j that does not persist any data when your application shuts down. You can explicitly disable that mode by setting spring.data.neo4j.embedded.enabled=false. You can also enable persistence for the embedded mode by providing a path to a database file, as shown in the following example:
spring.data.neo4j.uri=file://var/tmp/graph.db
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| The Neo4j OGM embedded driver does not provide the Neo4j kernel. Users are expected to provide this dependency manually. See the documentation for more details. |
By default, if you are running a web application, the session is bound to the thread for the entire processing of the request (that is, it uses the "Open Session in View" pattern). If you do not want this behavior, add the following line to your application.properties file:
spring.data.neo4j.open-in-view=false
Spring Data includes repository support for Neo4j.
In fact, both Spring Data JPA and Spring Data Neo4j share the same common infrastructure. You could take the JPA example from earlier and, assuming that City is now a Neo4j OGM @NodeEntity rather than a JPA @Entity, it works in the same way.
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| You can customize entity scanning locations by using the |
To enable repository support (and optionally support for @Transactional), add the following two annotations to your Spring configuration:
@EnableNeo4jRepositories(basePackages = "com.example.myapp.repository")
@EnableTransactionManagement
The following examples shows an interface definition for a Neo4j repository:
package com.example.myapp.domain;
import org.springframework.data.domain.*; import org.springframework.data.repository.*; public interface CityRepository extends GraphRepository<City> { Page<City> findAll(Pageable pageable); City findByNameAndCountry(String name, String country); }
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| For complete details of Spring Data Neo4j, including its rich object mapping technologies, refer to the reference documentation. |
Spring Data Gemfire provides convenient Spring-friendly tools for accessing the Pivotal Gemfire data management platform. There is a spring-boot-starter-data-gemfire ‘Starter’ for collecting the dependencies in a convenient way. There is currently no auto-configuration support for Gemfire, but you can enable Spring Data Repositories with a single annotation: @EnableGemfireRepositories.
Apache Solr is a search engine. Spring Boot offers basic auto-configuration for the Solr 5 client library and the abstractions on top of it provided by Spring Data Solr. There is a spring-boot-starter-data-solr ‘Starter’ for collecting the dependencies in a convenient way.
You can inject an auto-configured SolrClient instance as you would any other Spring bean. By default, the instance tries to connect to a server atlocalhost:8983/solr. The following example shows how to inject a Solr bean:
@Component public class MyBean { private SolrClient solr; @Autowired public MyBean(SolrClient solr) { this.solr = solr; } // ... }
If you add your own @Bean of type SolrClient, it replaces the default.
Spring Data includes repository support for Apache Solr. As with the JPA repositories discussed earlier, the basic principle is that queries are constructed for you automatically based on method names.
In fact, both Spring Data JPA and Spring Data Solr share the same common infrastructure. So you could take the JPA example from earlier and, assuming that City is now a @SolrDocument class rather than a JPA @Entity, it works in the same way.
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| For complete details of Spring Data Solr, refer to the reference documentation. |
Elasticsearch is an open source, distributed, real-time search and analytics engine. Spring Boot offers basic auto-configuration for Elasticsearch and the abstractions on top of it provided by Spring Data Elasticsearch. There is a spring-boot-starter-data-elasticsearch ‘Starter’ for collecting the dependencies in a convenient way. Spring Boot also supports Jest.
If you have Jest on the classpath, you can inject an auto-configured JestClient targeting localhost:9200 by default. You can further tune how the client is configured, as shown in the following example:
spring.elasticsearch.jest.uris=http://search.example.com:9200
spring.elasticsearch.jest.read-timeout=10000 spring.elasticsearch.jest.username=user spring.elasticsearch.jest.password=secret
You can also register an arbitrary number of beans that implement HttpClientConfigBuilderCustomizer for more advanced customizations. The following example tunes additional HTTP settings:
static class HttpSettingsCustomizer implements HttpClientConfigBuilderCustomizer { @Override public void customize(HttpClientConfig.Builder builder) { builder.maxTotalConnection(100).defaultMaxTotalConnectionPerRoute(5); } }
To take full control over the registration, define a JestClient bean.
To connect to Elasticsearch, you must provide the address of one or more cluster nodes. The address can be specified by setting the spring.data.elasticsearch.cluster-nodes property to a comma-separated ‘host:port’ list. With this configuration in place, an ElasticsearchTemplate or TransportClient can be injected like any other Spring bean, as shown in the following example:
spring.data.elasticsearch.cluster-nodes=localhost:9300
@Component public class MyBean { private final ElasticsearchTemplate template; public MyBean(ElasticsearchTemplate template) { this.template = template; } // ... }
If you add your own ElasticsearchTemplate or TransportClient @Bean, it replaces the default.
Spring Data includes repository support for Elasticsearch. As with the JPA repositories discussed earlier, the basic principle is that queries are constructed for you automatically based on method names.
In fact, both Spring Data JPA and Spring Data Elasticsearch share the same common infrastructure. You could take the JPA example from earlier and, assuming that City is now an Elasticsearch @Document class rather than a JPA @Entity, it works in the same way.
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| For complete details of Spring Data Elasticsearch, refer to the reference documentation. |
Cassandra is an open source, distributed database management system designed to handle large amounts of data across many commodity servers. Spring Boot offers auto-configuration for Cassandra and the abstractions on top of it provided by Spring Data Cassandra. There is a spring-boot-starter-data-cassandra ‘Starter’ for collecting the dependencies in a convenient way.
You can inject an auto-configured CassandraTemplate or a Cassandra Session instance as you would with any other Spring Bean. The spring.data.cassandra.*properties can be used to customize the connection. Generally, you provide keyspace-name and contact-points properties, as shown in the following example:
spring.data.cassandra.keyspace-name=mykeyspace
spring.data.cassandra.contact-points=cassandrahost1,cassandrahost2
The following code listing shows how to inject a Cassandra bean:
@Component public class MyBean { private CassandraTemplate template; @Autowired public MyBean(CassandraTemplate template) { this.template = template; } // ... }
If you add your own @Bean of type CassandraTemplate, it replaces the default.
Spring Data includes basic repository support for Cassandra. Currently, this is more limited than the JPA repositories discussed earlier and needs to annotate finder methods with @Query.
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| For complete details of Spring Data Cassandra, refer to the reference documentation. |
Couchbase is an open-source, distributed multi-model NoSQL document-oriented database that is optimized for interactive applications. Spring Boot offers auto-configuration for Couchbase and the abstractions on top of it provided by Spring Data Couchbase. There are a spring-boot-starter-data-couchbase and spring-boot-starter-data-couchbase-reactive ‘Starters’ for collecting the dependencies in a convenient way.
You can get a Bucket and Cluster by adding the Couchbase SDK and some configuration. The spring.couchbase.* properties can be used to customize the connection. Generally, you provide the bootstrap hosts, bucket name, and password, as shown in the following example:
spring.couchbase.bootstrap-hosts=my-host-1,192.168.1.123
spring.couchbase.bucket.name=my-bucket spring.couchbase.bucket.password=secret
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| You need to provide at least the bootstrap host(s), in which case the bucket name is |
It is also possible to customize some of the CouchbaseEnvironment settings. For instance, the following configuration changes the timeout to use to open a new Bucket and enables SSL support:
spring.couchbase.env.timeouts.connect=3000
spring.couchbase.env.ssl.key-store=/location/of/keystore.jks spring.couchbase.env.ssl.key-store-password=secret
Check the spring.couchbase.env.* properties for more details.
Spring Data includes repository support for Couchbase. For complete details of Spring Data Couchbase, refer to the reference documentation.
You can inject an auto-configured CouchbaseTemplate instance as you would with any other Spring Bean, provided a default CouchbaseConfigurer is available (which happens when you enable Couchbase support, as explained earlier).
The following examples shows how to inject a Couchbase bean:
@Component public class MyBean { private final CouchbaseTemplate template; @Autowired public MyBean(CouchbaseTemplate template) { this.template = template; } // ... }
There are a few beans that you can define in your own configuration to override those provided by the auto-configuration:
- A
CouchbaseTemplate@Beanwith a name ofcouchbaseTemplate. - An
IndexManager@Beanwith a name ofcouchbaseIndexManager. - A
CustomConversions@Beanwith a name ofcouchbaseCustomConversions.
To avoid hard-coding those names in your own config, you can reuse BeanNames provided by Spring Data Couchbase. For instance, you can customize the converters to use as follows:
@Configuration public class SomeConfiguration { @Bean(BeanNames.COUCHBASE_CUSTOM_CONVERSIONS) public CustomConversions myCustomConversions() { return new CustomConversions(...); } // ... }
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| If you want to fully bypass the auto-configuration for Spring Data Couchbase, provide your own implementation of |
LDAP (Lightweight Directory Access Protocol) is an open, vendor-neutral, industry standard application protocol for accessing and maintaining distributed directory information services over an IP network. Spring Boot offers auto-configuration for any compliant LDAP server as well as support for the embedded in-memory LDAP server from UnboundID.
LDAP abstractions are provided by Spring Data LDAP. There is a spring-boot-starter-data-ldap ‘Starter’ for collecting the dependencies in a convenient way.
To connect to an LDAP server, make sure you declare a dependency on the spring-boot-starter-data-ldap ‘Starter’ or spring-ldap-core and then declare the URLs of your server in your application.properties, as shown in the following example:
spring.ldap.urls=ldap://myserver:1235
spring.ldap.username=admin spring.ldap.password=secret
If you need to customize connection settings, you can use the spring.ldap.base and spring.ldap.base-environment properties.
Spring Data includes repository support for LDAP. For complete details of Spring Data LDAP, refer to the reference documentation.
You can also inject an auto-configured LdapTemplate instance as you would with any other Spring Bean, as shown in the following example:
@Component public class MyBean { private final LdapTemplate template; @Autowired public MyBean(LdapTemplate template) { this.template = template; } // ... }
For testing purposes Spring Boot supports auto-configuration of an in-memory LDAP server from UnboundID. To configure the server add a dependency to com.unboundid:unboundid-ldapsdk and declare a base-dn property:
spring.ldap.embedded.base-dn=dc=spring,dc=io
By default, the server starts on a random port and triggers the regular LDAP support. There is no need to specify a spring.ldap.urls property.
If there is a schema.ldif file on your classpath, it is used to initialize the server. If you want to load the initialization script from a different resource, you can also use the spring.ldap.embedded.ldif property.
By default, a standard schema is used to validate LDIF files, you can turn off validation altogether using the spring.ldap.embedded.validation.enabled property. If you have custom attributes, you can use spring.ldap.embedded.validation.schema to define your custom attribute types or object classes.
InfluxDB is an open-source time series database optimized for fast, high-availability storage and retrieval of time series data in fields such as operations monitoring, application metrics, Internet-of-Things sensor data, and real-time analytics.
Spring Boot auto-configures an InfluxDB instance, provided the influxdb-java client is on the classpath and the URL of the database is set, as shown in the following example:
spring.influx.url=http://172.0.0.1:8086
If the connection to InfluxDB requires a user and password, you can set the spring.influx.user and spring.influx.password properties accordingly.
InfluxDB relies on OkHttp. If you need to tune the http client InfluxDB uses behind the scenes, you can register an OkHttpClient.Builder bean.
The Spring Framework provides support for transparently adding caching to an application. At its core, the abstraction applies caching to methods, thus reducing the number of executions based on the information available in the cache. The caching logic is applied transparently, without any interference to the invoker. Spring Boot auto-configures the cache infrastructure as long as caching support is enabled via the @EnableCaching annotation.
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| Check the relevant section of the Spring Framework reference for more details. |
In a nutshell, adding caching to an operation of your service is as easy as adding the relevant annotation to its method, as shown in the following example:
import org.springframework.cache.annotation.Cacheable
import org.springframework.stereotype.Component; @Component public class MathService { @Cacheable("piDecimals") public int computePiDecimal(int i) { // ... } }
This example demonstrates the use of caching on a potentially costly operation. Before invoking computePiDecimal, the abstraction looks for an entry in the piDecimals cache that matches the i argument. If an entry is found, the content in the cache is immediately returned to the caller, and the method is not invoked. Otherwise, the method is invoked, and the cache is updated before returning the value.
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| You can also use the standard JSR-107 (JCache) annotations (such as |
If you do not add any specific cache library, Spring Boot auto-configures a simple provider that uses concurrent maps in memory. When a cache is required (such as piDecimals in the preceding example), this provider creates it for you. The simple provider is not really recommended for production usage, but it is great for getting started and making sure that you understand the features. When you have made up your mind about the cache provider to use, please make sure to read its documentation to figure out how to configure the caches that your application uses. Nearly all providers require you to explicitly configure every cache that you use in the application. Some offer a way to customize the default caches defined by the spring.cache.cache-names property.
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| If you use the cache infrastructure with beans that are not interface-based, make sure to enable the |
The cache abstraction does not provide an actual store and relies on abstraction materialized by the org.springframework.cache.Cache andorg.springframework.cache.CacheManager interfaces.
If you have not defined a bean of type CacheManager or a CacheResolver named cacheResolver (see CachingConfigurer), Spring Boot tries to detect the following providers (in the indicated order):
- Generic
- JCache (JSR-107) (EhCache 3, Hazelcast, Infinispan, and others)
- EhCache 2.x
- Hazelcast
- Infinispan
- Couchbase
- Redis
- Caffeine
- Simple
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| It is also possible to force a particular cache provider by setting the |
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| Use the |
If the CacheManager is auto-configured by Spring Boot, you can further tune its configuration before it is fully initialized by exposing a bean that implements theCacheManagerCustomizer interface. The following example sets a flag to say that null values should be passed down to the underlying map:
@Bean public CacheManagerCustomizer<ConcurrentMapCacheManager> cacheManagerCustomizer() { return new CacheManagerCustomizer<ConcurrentMapCacheManager>() { @Override public void customize(ConcurrentMapCacheManager cacheManager) { cacheManager.setAllowNullValues(false); } }; }
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| In the example above, an auto-configured |
Generic caching is used if the context defines at least one org.springframework.cache.Cache bean. A CacheManager wrapping all beans of that type is created.
JCache is bootstrapped via the presence of a javax.cache.spi.CachingProvider on the classpath (that is, a JSR-107 compliant caching library exists on the classpath) and the JCacheCacheManager provided by the spring-boot-starter-cache ‘Starter’. Various compliant libraries are available, and Spring Boot provides dependency management for Ehcache 3, Hazelcast, and Infinispan. Any other compliant library can be added as well.
It might happen that more than one provider is present, in which case the provider must be explicitly specified. Even if the JSR-107 standard does not enforce a standardized way to define the location of the configuration file, Spring Boot does its best to accommodate setting a cache with implementation details, as shown in the following example:
# Only necessary if more than one provider is present
spring.cache.jcache.provider=com.acme.MyCachingProvider spring.cache.jcache.config=classpath:acme.xml
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| When a cache library offers both a native implementation and JSR-107 support, Spring Boot prefers the JSR-107 support, so that the same features are available if you switch to a different JSR-107 implementation. |
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| Spring Boot has general support for Hazelcast. If a single |
There are two ways to customize the underlying javax.cache.cacheManager:
- Caches can be created on startup by setting the
spring.cache.cache-namesproperty. If a customjavax.cache.configuration.Configurationbean is defined, it is used to customize them. org.springframework.boot.autoconfigure.cache.JCacheManagerCustomizerbeans are invoked with the reference of theCacheManagerfor full customization.
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| If a standard |
EhCache 2.x is used if a file named ehcache.xml can be found at the root of the classpath. If EhCache 2.x is found, the EhCacheCacheManager provided by thespring-boot-starter-cache ‘Starter’ is used to bootstrap the cache manager. An alternate configuration file can be provided as well, as shown in the following example:
spring.cache.ehcache.config=classpath:config/another-config.xml
Spring Boot has general support for Hazelcast. If a HazelcastInstance has been auto-configured, it is automatically wrapped in a CacheManager.
Infinispan has no default configuration file location, so it must be specified explicitly. Otherwise, the default bootstrap is used.
spring.cache.infinispan.config=infinispan.xml
Caches can be created on startup by setting the spring.cache.cache-names property. If a custom ConfigurationBuilder bean is defined, it is used to customize the caches.
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| The support of Infinispan in Spring Boot is restricted to the embedded mode and is quite basic. If you want more options, you should use the official Infinispan Spring Boot starter instead. See Infinispan’s documentation for more details. |
If the Couchbase Java client and the couchbase-spring-cache implementation are available and Couchbase is configured, a CouchbaseCacheManager is auto-configured. It is also possible to create additional caches on startup by setting the spring.cache.cache-names property. These caches operate on the Bucket that was auto-configured. You can also create additional caches on another Bucket by using the customizer. Assume you need two caches (cache1 and cache2) on the "main" Bucket and one cache3 cache with a custom time to live of 2 seconds on the "another" Bucket. You can create the first two caches through configuration, as follows:
spring.cache.cache-names=cache1,cache2
Then you can define a @Configuration class to configure the extra Bucket and the cache3 cache, as follows:
@Configuration public class CouchbaseCacheConfiguration { private final Cluster cluster; public CouchbaseCacheConfiguration(Cluster cluster) { this.cluster = cluster; } @Bean public Bucket anotherBucket() { return this.cluster.openBucket("another", "secret"); } @Bean public CacheManagerCustomizer<CouchbaseCacheManager> cacheManagerCustomizer() { return c -> { c.prepareCache("cache3", CacheBuilder.newInstance(anotherBucket()) .withExpiration(2)); }; } }
This sample configuration reuses the Cluster that was created via auto-configuration.
If Redis is available and configured, a RedisCacheManager is auto-configured. It is possible to create additional caches on startup by setting thespring.cache.cache-names property and cache defaults can be configured using spring.redis.cache.* properties. For instance, the following configuration creates cache1 and cache2 caches with a time to live of 10 minutes:
spring.cache.cache-names=cache1,cache2
spring.cache.redis.time-to-live=600000
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| By default, a key prefix is added so that, if two separate caches use the same key, Redis does not have overlapping keys and cannot return invalid values. We strongly recommend keeping this setting enabled if you create your own |
Caffeine is a Java 8 rewrite of Guava’s cache that supersedes support for Guava. If Caffeine is present, a CaffeineCacheManager (provided by thespring-boot-starter-cache ‘Starter’) is auto-configured. Caches can be created on startup by setting the spring.cache.cache-names property and can be customized by one of the following (in the indicated order):
- A cache spec defined by
spring.cache.caffeine.spec - A
com.github.benmanes.caffeine.cache.CaffeineSpecbean is defined - A
com.github.benmanes.caffeine.cache.Caffeinebean is defined
For instance, the following configuration creates cache1 and cache2 caches with a maximum size of 500 and a time to live of 10 minutes
spring.cache.cache-names=cache1,cache2
spring.cache.caffeine.spec=maximumSize=500,expireAfterAccess=600s
If a com.github.benmanes.caffeine.cache.CacheLoader bean is defined, it is automatically associated to the CaffeineCacheManager. Since the CacheLoader is going to be associated with all caches managed by the cache manager, it must be defined as CacheLoader<Object, Object>. The auto-configuration ignores any other generic type.
If none of the other providers can be found, a simple implementation using a ConcurrentHashMap as the cache store is configured. This is the default if no caching library is present in your application. By default, caches are created as needed, but you can restrict the list of available caches by setting the cache-names property. For instance, if you want only cache1 and cache2 caches, set the cache-names property as follows:
spring.cache.cache-names=cache1,cache2
If you do so and your application uses a cache not listed, then it fails at runtime when the cache is needed, but not on startup. This is similar to the way the "real" cache providers behave if you use an undeclared cache.
When @EnableCaching is present in your configuration, a suitable cache configuration is expected as well. If you need to disable caching altogether in certain environments, force the cache type to none to use a no-op implementation, as shown in the following example:
spring.cache.type=none
The Spring Framework provides extensive support for integrating with messaging systems, from simplified use of the JMS API using JmsTemplate to a complete infrastructure to receive messages asynchronously. Spring AMQP provides a similar feature set for the ‘Advanced Message Queuing Protocol’. Spring Boot also provides auto-configuration options for RabbitTemplate and RabbitMQ. Spring WebSocket natively includes support for STOMP messaging, and Spring Boot has support for that through starters and a small amount of auto-configuration. Spring Boot also has support for Apache Kafka.
The javax.jms.ConnectionFactory interface provides a standard method of creating a javax.jms.Connection for interacting with a JMS broker. Although Spring needs a ConnectionFactory to work with JMS, you generally need not use it directly yourself and can instead rely on higher level messaging abstractions. (See therelevant section of the Spring Framework reference documentation for details.) Spring Boot also auto-configures the necessary infrastructure to send and receive messages.
When ActiveMQ is available on the classpath, Spring Boot can also configure a ConnectionFactory. If the broker is present, an embedded broker is automatically started and configured (provided no broker URL is specified through configuration).
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| If you use |
ActiveMQ configuration is controlled by external configuration properties in spring.activemq.*. For example, you might declare the following section inapplication.properties:
spring.activemq.broker-url=tcp://192.168.1.210:9876
spring.activemq.user=admin spring.activemq.password=secret
You can also pool JMS resources by adding a dependency to org.apache.activemq:activemq-pool and configuring the PooledConnectionFactory accordingly, as shown in the following example:
spring.activemq.pool.enabled=true
spring.activemq.pool.max-connections=50
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| See |
By default, ActiveMQ creates a destination if it does not yet exist so that destinations are resolved against their provided names.
Spring Boot can auto-configure a ConnectionFactory when it detects that Artemis is available on the classpath. If the broker is present, an embedded broker is automatically started and configured (unless the mode property has been explicitly set). The supported modes are embedded (to make explicit that an embedded broker is required and that an error should occur if the broker is not available on the classpath) and native (to connect to a broker using the netty transport protocol). When the latter is configured, Spring Boot configures a ConnectionFactory that connects to a broker running on the local machine with the default settings.
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| If you are using |
Artemis configuration is controlled by external configuration properties in spring.artemis.*. For example, you might declare the following section inapplication.properties:
spring.artemis.mode=native
spring.artemis.host=192.168.1.210 spring.artemis.port=9876 spring.artemis.user=admin spring.artemis.password=secret
When embedding the broker, you can choose if you want to enable persistence and list the destinations that should be made available. These can be specified as a comma-separated list to create them with the default options, or you can define bean(s) of typeorg.apache.activemq.artemis.jms.server.config.JMSQueueConfiguration or org.apache.activemq.artemis.jms.server.config.TopicConfiguration, for advanced queue and topic configurations, respectively.
See ArtemisProperties for more supported options.
No JNDI lookup is involved, and destinations are resolved against their names, using either the ‘name’ attribute in the Artemis configuration or the names provided through configuration.
If you are running your application in an application server, Spring Boot tries to locate a JMS ConnectionFactory by using JNDI. By default, the java:/JmsXA andjava:/XAConnectionFactory location are checked. You can use the spring.jms.jndi-name property if you need to specify an alternative location, as shown in the following example:
spring.jms.jndi-name=java:/MyConnectionFactory
Spring’s JmsTemplate is auto-configured, and you can autowire it directly into your own beans, as shown in the following example:
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jms.core.JmsTemplate; import org.springframework.stereotype.Component; @Component public class MyBean { private final JmsTemplate jmsTemplate; @Autowired public MyBean(JmsTemplate jmsTemplate) { this.jmsTemplate = jmsTemplate; } // ... }
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When the JMS infrastructure is present, any bean can be annotated with @JmsListener to create a listener endpoint. If no JmsListenerContainerFactory has been defined, a default one is configured automatically. If a DestinationResolver or a MessageConverter beans is defined, it is associated automatically to the default factory.
By default, the default factory is transactional. If you run in an infrastructure where a JtaTransactionManager is present, it is associated to the listener container by default. If not, the sessionTransacted flag is enabled. In that latter scenario, you can associate your local data store transaction to the processing of an incoming message by adding @Transactional on your listener method (or a delegate thereof). This ensures that the incoming message is acknowledged, once the local transaction has completed. This also includes sending response messages that have been performed on the same JMS session.
The following component creates a listener endpoint on the someQueue destination:
@Component public class MyBean { @JmsListener(destination = "someQueue") public void processMessage(String content) { // ... } }
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If you need to create more JmsListenerContainerFactory instances or if you want to override the default, Spring Boot provides aDefaultJmsListenerContainerFactoryConfigurer that you can use to initialize a DefaultJmsListenerContainerFactory with the same settings as the one that is auto-configured.
For instance, the following example exposes another factory that uses a specific MessageConverter:
@Configuration static class JmsConfiguration { @Bean public DefaultJmsListenerContainerFactory myFactory( DefaultJmsListenerContainerFactoryConfigurer configurer) { DefaultJmsListenerContainerFactory factory = new DefaultJmsListenerContainerFactory(); configurer.configure(factory, connectionFactory()); factory.setMessageConverter(myMessageConverter()); return factory; } }
Then you can use the factory in any @JmsListener-annotated method as follows:
@Component public class MyBean { @JmsListener(destination = "someQueue", containerFactory="myFactory") public void processMessage(String content) { // ... } }
The Advanced Message Queuing Protocol (AMQP) is a platform-neutral, wire-level protocol for message-oriented middleware. The Spring AMQP project applies core Spring concepts to the development of AMQP-based messaging solutions. Spring Boot offers several conveniences for working with AMQP through RabbitMQ, including the spring-boot-starter-amqp ‘Starter’.
RabbitMQ is a lightweight, reliable, scalable, and portable message broker based on the AMQP protocol. Spring uses RabbitMQ to communicate through the AMQP protocol.
RabbitMQ configuration is controlled by external configuration properties in spring.rabbitmq.*. For example, you might declare the following section inapplication.properties:
spring.rabbitmq.host=localhost
spring.rabbitmq.port=5672 spring.rabbitmq.username=admin spring.rabbitmq.password=secret
See RabbitProperties for more of the supported options.
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| See Understanding AMQP, the protocol used by RabbitMQ for more details. |
Spring’s AmqpTemplate and AmqpAdmin are auto-configured, and you can autowire them directly into your own beans, as shown in the following example:
import org.springframework.amqp.core.AmqpAdmin;
import org.springframework.amqp.core.AmqpTemplate; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Component; @Component public class MyBean { private final AmqpAdmin amqpAdmin; private final AmqpTemplate amqpTemplate; @Autowired public MyBean(AmqpAdmin amqpAdmin, AmqpTemplate amqpTemplate) { this.amqpAdmin = amqpAdmin; this.amqpTemplate = amqpTemplate; } // ... }
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If necessary, any org.springframework.amqp.core.Queue that is defined as a bean is automatically used to declare a corresponding queue on the RabbitMQ instance.
To retry operations, you can enable retries on the AmqpTemplate (for example, in the event that the broker connection is lost). Retries are disabled by default.
When the Rabbit infrastructure is present, any bean can be annotated with @RabbitListener to create a listener endpoint. If no RabbitListenerContainerFactoryhas been defined, a default SimpleRabbitListenerContainerFactory is automatically configured and you can switch to a direct container using thespring.rabbitmq.listener.type property. If a MessageConverter or a MessageRecoverer bean is defined, it is automatically associated with the default factory.
The following sample component creates a listener endpoint on the someQueue queue:
@Component public class MyBean { @RabbitListener(queues = "someQueue") public void processMessage(String content) { // ... } }
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If you need to create more RabbitListenerContainerFactory instances or if you want to override the default, Spring Boot provides aSimpleRabbitListenerContainerFactoryConfigurer and a DirectRabbitListenerContainerFactoryConfigurer that you can use to initialize aSimpleRabbitListenerContainerFactory and a DirectRabbitListenerContainerFactory with the same settings as the factories used by the auto-configuration.
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For instance, the following configuration class exposes another factory that uses a specific MessageConverter:
@Configuration static class RabbitConfiguration { @Bean public SimpleRabbitListenerContainerFactory myFactory( SimpleRabbitListenerContainerFactoryConfigurer configurer) { SimpleRabbitListenerContainerFactory factory = new SimpleRabbitListenerContainerFactory(); configurer.configure(factory, connectionFactory); factory.setMessageConverter(myMessageConverter()); return factory; } }
Then you can use the factory in any @RabbitListener-annotated method as follows:
@Component public class MyBean { @RabbitListener(queues = "someQueue", containerFactory="myFactory") public void processMessage(String content) { // ... } }
You can enable retries to handle situations where your listener throws an exception. By default, RejectAndDontRequeueRecoverer is used, but you can define a MessageRecoverer of your own. When retries are exhausted, the message is rejected and either dropped or routed to a dead-letter exchange if the broker is configured to do so. By default, retries are disabled.
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| By default, if retries are disabled and the listener throws an exception, the delivery is retried indefinitely. You can modify this behavior in two ways: Set the |
Apache Kafka is supported by providing auto-configuration of the spring-kafka project.
Kafka configuration is controlled by external configuration properties in spring.kafka.*. For example, you might declare the following section inapplication.properties:
spring.kafka.bootstrap-servers=localhost:9092
spring.kafka.consumer.group-id=myGroup
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See KafkaProperties for more supported options.
Spring’s KafkaTemplate is auto-configured, and you can autowire it directly in your own beans, as shown in the following example:
@Component public class MyBean { private final KafkaTemplate kafkaTemplate; @Autowired public MyBean(KafkaTemplate kafkaTemplate) { this.kafkaTemplate = kafkaTemplate; } // ... }
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When the Apache Kafka infrastructure is present, any bean can be annotated with @KafkaListener to create a listener endpoint. If no KafkaListenerContainerFactory has been defined, a default one is automatically configured with keys defined in spring.kafka.listener.*. Also, if a RecordMessageConverter bean is defined, it is automatically associated to the default factory.
The following component creates a listener endpoint on the someTopic topic:
@Component public class MyBean { @KafkaListener(topics = "someTopic") public void processMessage(String content) { // ... } }
The properties supported by auto configuration are shown in Appendix A, Common application properties. Note that, for the most part, these properties (hyphenated or camelCase) map directly to the Apache Kafka dotted properties. Refer to the Apache Kafka documentation for details.
The first few of these properties apply to both producers and consumers but can be specified at the producer or consumer level if you wish to use different values for each. Apache Kafka designates properties with an importance of HIGH, MEDIUM, or LOW. Spring Boot auto-configuration supports all HIGH importance properties, some selected MEDIUM and LOW properties, and any properties that do not have a default value.
Only a subset of the properties supported by Kafka are available through the KafkaProperties class. If you wish to configure the producer or consumer with additional properties that are not directly supported, use the following properties:
spring.kafka.properties.foo.bar=baz
spring.kafka.consumer.properties.fiz.buz=qux spring,kafka.producer.properties.baz.qux=fiz
This sets the common foo.bar Kafka property to baz (applies to both producers and consumers), the consumer fiz.buz property to qux and the baz.quxproducer property to fiz.
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If you need to call remote REST services from your application, you can use the Spring Framework’s RestTemplate class. Since RestTemplate instances often need to be customized before being used, Spring Boot does not provide any single auto-configured RestTemplate bean. It does, however, auto-configure a RestTemplateBuilder, which can be used to create RestTemplate instances when needed. The auto-configured RestTemplateBuilder ensures that sensible HttpMessageConverters are applied to RestTemplate instances.
The following code shows a typical example:
@Service public class MyService { private final RestTemplate restTemplate; public MyBean(RestTemplateBuilder restTemplateBuilder) { this.restTemplate = restTemplateBuilder.build(); } public Details someRestCall(String name) { return this.restTemplate.getForObject("/{name}/details", Details.class, name); } }
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There are three main approaches to RestTemplate customization, depending on how broadly you want the customizations to apply.
To make the scope of any customizations as narrow as possible, inject the auto-configured RestTemplateBuilder and then call its methods as required. Each method call returns a new RestTemplateBuilder instance, so the customizations only affect this use of the builder.
To make an application-wide, additive customization, use a RestTemplateCustomizer bean. All such beans are automatically registered with the auto-configured RestTemplateBuilder and are applied to any templates that are built with it.
The following example shows a customizer that configures the use of a proxy for all hosts except 192.168.0.5:
static class ProxyCustomizer implements RestTemplateCustomizer { @Override public void customize(RestTemplate restTemplate) { HttpHost proxy = new HttpHost("proxy.example.com"); HttpClient httpClient = HttpClientBuilder.create() .setRoutePlanner(new DefaultProxyRoutePlanner(proxy) { @Override public HttpHost determineProxy(HttpHost target, HttpRequest request, HttpContext context) throws HttpException { if (target.getHostName().equals("192.168.0.5")) { return null; } return super.determineProxy(target, request, context); } }).build(); restTemplate.setRequestFactory( new HttpComponentsClientHttpRequestFactory(httpClient)); } }
Finally, the most extreme (and rarely used) option is to create your own RestTemplateBuilder bean. Doing so switches off the auto-configuration of aRestTemplateBuilder and prevents any RestTemplateCustomizer beans from being used.
If you have Spring WebFlux on your classpath, you can also choose to use WebClient to call remote REST services, Compared to RestTemplate, this client has a more functional feel and is fully reactive. You can create your own client instance with the builder, WebClient.create(). See the relevant section on WebClient.
Spring Boot creates and pre-configures such a builder for you. For example, client HTTP codecs are configured in the same fashion as the server ones (see WebFlux HTTP codecs auto-configuration).
The following code shows a typical example:
@Service public class MyService { private final WebClient webClient; public MyBean(WebClient.Builder webClientBuilder) { this.webClient = webClientBuilder.baseUrl("http://example.org").build(); } public Mono<Details> someRestCall(String name) { return this.webClient.get().url("/{name}/details", name) .retrieve().bodyToMono(Details.class); } }
There are three main approaches to WebClient customization, depending on how broadly you want the customizations to apply.
To make the scope of any customizations as narrow as possible, inject the auto-configured WebClient.Builder and then call its methods as required. WebClient.Builder instances are stateful: Any change on the builder is reflected in all clients subsequently created with it. If you want to create several clients with the same builder, you can also consider cloning the builder with WebClient.Builder other = builder.clone();.
To make an application-wide, additive customization to all WebClient.Builder instances, you can declare WebClientCustomizer beans and change the WebClient.Builder locally at the point of injection.
Finally, you can fall back to the original API and use WebClient.create(). In that case, no auto-configuration or WebClientCustomizer is applied.
The method validation feature supported by Bean Validation 1.1 is automatically enabled as long as a JSR-303 implementation (such as Hibernate validator) is on the classpath. This lets bean methods be annotated with javax.validation constraints on their parameters and/or on their return value. Target classes with such annotated methods need to be annotated with the @Validated annotation at the type level for their methods to be searched for inline constraint annotations.
For instance, the following service triggers the validation of the first argument, making sure its size is between 8 and 10:
@Service @Validated public class MyBean { public Archive findByCodeAndAuthor(@Size(min = 8, max = 10) String code, Author author) { ... } }
The Spring Framework provides an easy abstraction for sending email by using the JavaMailSender interface, and Spring Boot provides auto-configuration for it as well as a starter module.
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If spring.mail.host and the relevant libraries (as defined by spring-boot-starter-mail) are available, a default JavaMailSender is created if none exists. The sender can be further customized by configuration items from the spring.mail namespace, see MailProperties for more details.
In particular, certain default timeout values are infinite, and you may want to change that to avoid having a thread blocked by an unresponsive mail server, as shown in the following example:
spring.mail.properties.mail.smtp.connectiontimeout=5000
spring.mail.properties.mail.smtp.timeout=3000 spring.mail.properties.mail.smtp.writetimeout=5000
Spring Boot supports distributed JTA transactions across multiple XA resources by using either an Atomikos or Bitronix embedded transaction manager. JTA transactions are also supported when deploying to a suitable Java EE Application Server.
When a JTA environment is detected, Spring’s JtaTransactionManager is used to manage transactions. Auto-configured JMS, DataSource, and JPA beans are upgraded to support XA transactions. You can use standard Spring idioms, such as @Transactional, to participate in a distributed transaction. If you are within a JTA environment and still want to use local transactions, you can set the spring.jta.enabled property to false to disable the JTA auto-configuration.
Atomikos is a popular open source transaction manager which can be embedded into your Spring Boot application. You can use the spring-boot-starter-jta-atomikos Starter to pull in the appropriate Atomikos libraries. Spring Boot auto-configures Atomikos and ensures that appropriate depends-on settings are applied to your Spring beans for correct startup and shutdown ordering.
By default Atomikos transaction logs are written to a transaction-logs directory in your application home directory (the directory in which your application jar file resides). You can customize this directory by setting a spring.jta.log-dir property in your application.properties file. Properties starting withspring.jta.atomikos.properties can also be used to customize the Atomikos UserTransactionServiceImp. See the AtomikosProperties Javadoc for complete details.
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Bitronix is popular open source JTA transaction manager implementation. You can use the spring-boot-starter-jta-bitronix starter to add the appropriate Bitronix dependencies to your project. As with Atomikos, Spring Boot automatically configures Bitronix and post-processes your beans to ensure that startup and shutdown ordering is correct.
By default, Bitronix transaction log files (part1.btm and part2.btm) are written to a transaction-logs directory in your application home directory. You can customize this directory by setting the spring.jta.log-dir property. Properties starting with spring.jta.bitronix.properties are also bound to the bitronix.tm.Configuration bean, allowing for complete customization. See the Bitronix documentation for details.
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| To ensure that multiple transaction managers can safely coordinate the same resource managers, each Bitronix instance must be configured with a unique ID. By default, this ID is the IP address of the machine on which Bitronix is running. To ensure uniqueness in production, you should configure the |
Narayana is popular open source JTA transaction manager implementation supported by JBoss. You can use the spring-boot-starter-jta-narayana starter to add the appropriate Narayana dependencies to your project. As with Atomikos and Bitronix, Spring Boot automatically configures Narayana and post-processes your beans to ensure that startup and shutdown ordering is correct.
By default, Narayana transaction logs are written to a transaction-logs directory in your application home directory (the directory in which your application jar file resides). You can customize this directory by setting a spring.jta.log-dir property in your application.properties file. Properties starting withspring.jta.narayana.properties can also be used to customize the Narayana configuration. See the NarayanaProperties Javadoc for complete details.
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If you package your Spring Boot application as a war or ear file and deploy it to a Java EE application server, you can use your application server’s built-in transaction manager. Spring Boot tries to auto-configure a transaction manager by looking at common JNDI locations (java:comp/UserTransaction, java:comp/TransactionManager, and so on). If you use a transaction service provided by your application server, you generally also want to ensure that all resources are managed by the server and exposed over JNDI. Spring Boot tries to auto-configure JMS by looking for a ConnectionFactory at the JNDI path (java:/JmsXA or java:/XAConnectionFactory), and you can use the spring.datasource.jndi-name property to configure your DataSource.
When using JTA, the primary JMS ConnectionFactory bean is XA aware and participates in distributed transactions. In some situations, you might want to process certain JMS messages using a non-XA ConnectionFactory. For example, your JMS processing logic might take longer than the XA timeout.
If you want to use a non-XA ConnectionFactory, you can inject the nonXaJmsConnectionFactory bean rather than the @Primary jmsConnectionFactory bean. For consistency the jmsConnectionFactory bean is also provided by using the bean alias xaJmsConnectionFactory.
The following example shows how to inject ConnectionFactory instances:
// Inject the primary (XA aware) ConnectionFactory
@Autowired
private ConnectionFactory defaultConnectionFactory; // Inject the XA aware ConnectionFactory (uses the alias and injects the same as above) @Autowired @Qualifier("xaJmsConnectionFactory") private ConnectionFactory xaConnectionFactory; // Inject the non-XA aware ConnectionFactory @Autowired @Qualifier("nonXaJmsConnectionFactory") private ConnectionFactory nonXaConnectionFactory;
The XAConnectionFactoryWrapper and XADataSourceWrapper interfaces can be used to support alternative embedded transaction managers. The interfaces are responsible for wrapping XAConnectionFactory and XADataSource beans and exposing them as regular ConnectionFactory and DataSource beans, which transparently enroll in the distributed transaction. DataSource and JMS auto-configuration use JTA variants, provided you have a JtaTransactionManager bean and appropriate XA wrapper beans registered within your ApplicationContext.
The BitronixXAConnectionFactoryWrapper and BitronixXADataSourceWrapper provide good examples of how to write XA wrappers.
If Hazelcast is on the classpath and a suitable configuration is found, Spring Boot auto-configures a HazelcastInstance that you can inject in your application.
If you define a com.hazelcast.config.Config bean, Spring Boot uses that. If your configuration defines an instance name, Spring Boot tries to locate an existing instance rather than creating a new one.
You could also specify the hazelcast.xml configuration file to use via configuration, as shown in the following example:
spring.hazelcast.config=classpath:config/my-hazelcast.xml
Otherwise, Spring Boot tries to find the Hazelcast configuration from the default locations: hazelcast.xml in the working directory or at the root of the classpath. We also check if the hazelcast.config system property is set. See the Hazelcast documentation for more details.
If hazelcast-client is present on the classpath, Spring Boot first attempts to create a client by checking the following configuration options:
- The presence of a
com.hazelcast.client.config.ClientConfigbean. - A configuration file defined by the
spring.hazelcast.configproperty. - The presence of the
hazelcast.client.configsystem property. - A
hazelcast-client.xmlin the working directory or at the root of the classpath.
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| Spring Boot also has explicit caching support for Hazelcast. If caching is enabled, the |
Spring Boot offers several conveniences for working with the Quartz scheduler, including the spring-boot-starter-quartz ‘Starter’. If Quartz is available, a Scheduler is auto-configured (via the SchedulerFactoryBean abstraction).
Beans of the following types are automatically picked up and associated with the Scheduler:
JobDetail: defines a particular Job.JobDetailinstances can be built with theJobBuilderAPI.Calendar.Trigger: defines when a particular job is triggered.
By default, an in-memory JobStore is used. However, it is possible to configure a JDBC-based store if a DataSource bean is available in your application and if thespring.quartz.job-store-type property is configured accordingly, as shown in the following example:
spring.quartz.job-store-type=jdbc
When the jdbc store is used, the schema can be initialized on startup, as shown in the following example:
spring.quartz.jdbc.initialize-schema=true
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| By default, the database is detected and initialized by using the standard scripts provided with the Quartz library. It is also possible to provide a custom script by setting the |
Quartz Scheduler configuration can be customized by using Quartz configuration properties ()spring.quartz.properties.*) and SchedulerFactoryBeanCustomizer beans, which allow programmatic SchedulerFactoryBean customization.
Jobs can define setters to inject data map properties. Regular beans can also be injected in a similar manner, as shown in the following example:
public class SampleJob extends QuartzJobBean { private MyService myService; private String name; // Inject "MyService" bean public void setMyService(MyService myService) { ... } // Inject the "name" job data property public void setName(String name) { ... } @Override protected void executeInternal(JobExecutionContext context) throws JobExecutionException { ... } }
Spring Boot offers several conveniences for working with Spring Integration, including the spring-boot-starter-integration ‘Starter’. Spring Integration provides abstractions over messaging and also other transports such as HTTP, TCP, and others. If Spring Integration is available on your classpath, it is initialized through the@EnableIntegration annotation.
Spring Boot also configures some features that are triggered by the presence of additional Spring Integration modules. If 'spring-integration-jmx' is also on the classpath, message processing statistics are published over JMX . If 'spring-integration-jdbc' is available, the default database schema can be created on startup, as shown in the following line:
spring.integration.jdbc.initialize-schema=always
See the IntegrationAutoConfiguration and IntegrationProperties classes for more details.
Spring Boot provides Spring Session auto-configuration for a wide range of data stores. When building a Servlet web application, the following stores can be auto-configured:
- JDBC
- Redis
- Hazelcast
- MongoDB
When building a reactive web application, the following stores can be auto-configured:
- Redis
- MongoDB
If Spring Session is available, you must choose the StoreType that you wish to use to store the sessions. For instance, to use JDBC as the back-end store, you can configure your application as follows:
spring.session.store-type=jdbc
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Each store has specific additional settings. For instance, it is possible to customize the name of the table for the JDBC store, as shown in the following example:
spring.session.jdbc.table-name=SESSIONS
Java Management Extensions (JMX) provide a standard mechanism to monitor and manage applications. By default, Spring Boot creates an MBeanServer a bean with an ID of ‘mbeanServer’ and exposes any of your beans that are annotated with Spring JMX annotations (@ManagedResource, @ManagedAttribute, and @ManagedOperation).
See the JmxAutoConfiguration class for more details.
Spring Boot provides a number of utilities and annotations to help when testing your application. Test support is provided by two modules; spring-boot-test contains core items, and spring-boot-test-autoconfigure supports auto-configuration for tests.
Most developers use the spring-boot-starter-test ‘Starter’, which imports both Spring Boot test modules as well as JUnit, AssertJ, Hamcrest, and a number of other useful libraries.
The spring-boot-starter-test ‘Starter’ (in the test scope)contains the following provided libraries:
- JUnit: The de-facto standard for unit testing Java applications.
- Spring Test & Spring Boot Test: Utilities and integration test support for Spring Boot applications.
- AssertJ: A fluent assertion library.
- Hamcrest: A library of matcher objects (also known as constraints or predicates).
- Mockito: A Java mocking framework.
- JSONassert: An assertion library for JSON.
- JsonPath: XPath for JSON.
We generally find these common libraries to be useful when writing tests. If these libraries do not suit your needs, you can add additional test dependencies of your own.
One of the major advantages of dependency injection is that it should make your code easier to unit test. You can instantiate objects using the new operator without even involving Spring. You can also use mock objects instead of real dependencies.
Often, you need to move beyond ‘unit testing’ and start ‘integration testing’ (with a Spring ApplicationContext). It is useful to be able to perform integration testing without requiring deployment of your application or needing to connect to other infrastructure.
The Spring Framework includes a dedicated test module for such integration testing. You can declare a dependency directly to org.springframework:spring-test or use the spring-boot-starter-test ‘Starter’ to pull it in transitively.
If you have not used the spring-test module before, you should start by reading the relevant section of the Spring Framework reference documentation.
A Spring Boot application is a Spring ApplicationContext, so nothing very special has to be done to test it beyond what you would normally do with a vanilla Spring context. One thing to watch out for, though, is that the external properties, logging, and other features of Spring Boot are installed in the context by default only if you useSpringApplication to create it.
Spring Boot provides a @SpringBootTest annotation, which can be used as an alternative to the standard spring-test @ContextConfiguration annotation when you need Spring Boot features. The annotation works by creating the ApplicationContext used in your tests through SpringApplication.
You can use the webEnvironment attribute of @SpringBootTest to further refine how your tests run:
MOCK: Loads aWebApplicationContextand provides a mock servlet environment. Embedded servlet containers are not started when using this annotation. If servlet APIs are not on your classpath, this mode transparently falls back to creating a regular non-webApplicationContext. It can be used in conjunction with@AutoConfigureMockMvcforMockMvc-based testing of your application.RANDOM_PORT: Loads anServletWebServerApplicationContextand provides a real servlet environment. Embedded servlet containers are started and listen on a random port.DEFINED_PORT: Loads aServletWebServerApplicationContextand provides a real servlet environment. Embedded servlet containers are started and listen on a defined port (from yourapplication.propertiesor on the default port of8080).NONE: Loads anApplicationContextby usingSpringApplicationbut does not provide any servlet environment (mock or otherwise).
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If you are familiar with the Spring Test Framework, you may be used to using @ContextConfiguration(classes=…) in order to specify which Spring @Configurationto load. Alternatively, you might have often used nested @Configuration classes within your test.
When testing Spring Boot applications, this is often not required. Spring Boot’s @*Test annotations search for your primary configuration automatically whenever you do not explicitly define one.
The search algorithm works up from the package that contains the test until it finds a class annotated with @SpringBootApplication or @SpringBootConfiguration. As long as you structured your code in a sensible way, your main configuration is usually found.
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| If you use a test annotation to test a more specific slice of your application, you should avoid adding configuration settings that are specific to a particular area on the main method’s application class. |
If you want to customize the primary configuration, you can use a nested @TestConfiguration class. Unlike a nested @Configuration class, which would be used instead of your application’s primary configuration, a nested @TestConfiguration class is used in addition to your application’s primary configuration.
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| Spring’s test framework caches application contexts between tests. Therefore, as long as your tests share the same configuration (no matter how it’s discovered), the potentially time-consuming process of loading the context happens only once. |
If your application uses component scanning, for example if you use @SpringBootApplication or @ComponentScan, you may find top-level configuration classes created only for specific tests accidentally get picked up everywhere.
As we have seen earlier, @TestConfiguration can be used on an inner class of a test to customize the primary configuration. When placed on a top-level class, @TestConfiguration indicates that classes in src/test/java should not be picked up by scanning. You can then import that class explicitly where it is required, as shown in the following example:
@RunWith(SpringRunner.class) @SpringBootTest @Import(MyTestsConfiguration.class) public class MyTests { @Test public void exampleTest() { ... } }
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If you need to start a full running server for tests, we recommend that you use random ports. If you use @SpringBootTest(webEnvironment=WebEnvironment.RANDOM_PORT), an available port is picked at random each time your test runs.
The @LocalServerPort annotation can be used to inject the actual port used into your test. For convenience, tests that need to make REST calls to the started server can additionally @Autowire a TestRestTemplate, which resolves relative links to the running server, as shown in the following example:
import org.junit.Test;
import org.junit.runner.RunWith; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.test.context.SpringBootTest; import org.springframework.boot.test.context.SpringBootTest.WebEnvironment; import org.springframework.boot.test.web.client.TestRestTemplate; import org.springframework.test.context.junit4.SpringRunner; import static org.assertj.core.api.Assertions.assertThat; @RunWith(SpringRunner.class) @SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT) public class RandomPortExampleTests { @Autowired private TestRestTemplate restTemplate; @Test public void exampleTest() { String body = this.restTemplate.getForObject("/", String.class); assertThat(body).isEqualTo("Hello World"); } }
When running tests, it is sometimes necessary to mock certain components within your application context. For example, you may have a facade over some remote service that is unavailable during development. Mocking can also be useful when you want to simulate failures that might be hard to trigger in a real environment.
Spring Boot includes a @MockBean annotation that can be used to define a Mockito mock for a bean inside your ApplicationContext. You can use the annotation to add new beans or replace a single existing bean definition. The annotation can be used directly on test classes, on fields within your test, or on @Configurationclasses and fields. When used on a field, the instance of the created mock is also injected. Mock beans are automatically reset after each test method.
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| If your test uses one of Spring Boot’s test annotations (such as @TestExecutionListeners(MockitoTestExecutionListener.class) |
The following example replaces an existing RemoteService bean with a mock implementation:
import org.junit.*;
import org.junit.runner.*; import org.springframework.beans.factory.annotation.*; import org.springframework.boot.test.context.*; import org.springframework.boot.test.mock.mockito.*; import org.springframework.test.context.junit4.*; import static org.assertj.core.api.Assertions.*; import static org.mockito.BDDMockito.*; @RunWith(SpringRunner.class) @SpringBootTest public class MyTests { @MockBean private RemoteService remoteService; @Autowired private Reverser reverser; @Test public void exampleTest() { // RemoteService has been injected into the reverser bean given(this.remoteService.someCall()).willReturn("mock"); String reverse = reverser.reverseSomeCall(); assertThat(reverse).isEqualTo("kcom"); } }
Additionally, you can use @SpyBean to wrap any existing bean with a Mockito spy. See the Javadoc for full details.
Spring Boot’s auto-configuration system works well for applications but can sometimes be a little too much for tests. It often helps to load only the parts of the configuration that are required to test a ‘slice’ of your application. For example, you might want to test that Spring MVC controllers are mapping URLs correctly, and you don’t want to involve database calls in those tests, or you might want to test JPA entities, and you are not interested in the web layer when those tests run.
The spring-boot-test-autoconfigure module includes a number of annotations that can be used to automatically configure such ‘slices’. Each of them works in a similar way, providing a @…Test annotation that loads the ApplicationContext and one or more @AutoConfigure… annotations that can be used to customize auto-configuration settings.
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| Each slice loads a very restricted set of auto-configuration classes. If you need to exclude one of them, most |
|
| It is also possible to use the |
To test that object JSON serialization and deserialization is working as expected you can use the @JsonTest annotation. @JsonTest auto-configures the available supported JSON mapper, which can be one of the following libraries:
- Jackson
ObjectMapper, any@JsonComponentbeans and any JacksonModules GsonJsonb
If you need to configure elements of the auto-configuration, you can use the @AutoConfigureJsonTesters annotation.
Spring Boot includes AssertJ-based helpers that work with the JSONassert and JsonPath libraries to check that JSON is as expected. The JacksonTester, GsonTester, JsonbTester, and BasicJsonTester classes can be used for Jackson, Gson, Jsonb, and Strings respectively. Any helper fields on the test class can be @Autowired when using @JsonTest. The following example shows a test class for Jackson:
import org.junit.*;
import org.junit.runner.*; import org.springframework.beans.factory.annotation.*; import org.springframework.boot.test.autoconfigure.json.*; import org.springframework.boot.test.context.*; import org.springframework.boot.test.json.*; import org.springframework.test.context.junit4.*; import static org.assertj.core.api.Assertions.*; @RunWith(SpringRunner.class) @JsonTest public class MyJsonTests { @Autowired private JacksonTester<VehicleDetails> json; @Test public void testSerialize() throws Exception { VehicleDetails details = new VehicleDetails("Honda", "Civic"); // Assert against a `.json` file in the same package as the test assertThat(this.json.write(details)).isEqualToJson("expected.json"); // Or use JSON path based assertions assertThat(this.json.write(details)).hasJsonPathStringValue("@.make"); assertThat(this.json.write(details)).extractingJsonPathStringValue("@.make") .isEqualTo("Honda"); } @Test public void testDeserialize() throws Exception { String content = "{\"make\":\"Ford\",\"model\":\"Focus\"}"; assertThat(this.json.parse(content)) .isEqualTo(new VehicleDetails("Ford", "Focus")); assertThat(this.json.parseObject(content).getMake()).isEqualTo("Ford"); } }
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| JSON helper classes can also be used directly in standard unit tests. Simply call the |
A list of the auto-configuration that is enabled by @JsonTest can be found in the appendix.
To test Spring MVC controllers are working as expected, you can use the @WebMvcTest annotation. @WebMvcTest auto-configures the Spring MVC infrastructure and limits scanned beans to @Controller, @ControllerAdvice, @JsonComponent, @Converter, Filter, WebMvcConfigurer, and HandlerMethodArgumentResolver. Regular @Component beans are not scanned when using this annotation.
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| If you need to register extra components such as Jackson |
Often, @WebMvcTest is limited to a single controller and is used in combination with @MockBean to provide mock implementations for required collaborators.
@WebMvcTest also auto-configures MockMvc. Mock MVC offers a powerful way to quickly test MVC controllers without needing to start a full HTTP server.
|
| You can also auto-configure |
import org.junit.*;
import org.junit.runner.*; import org.springframework.beans.factory.annotation.*; import org.springframework.boot.test.autoconfigure.web.servlet.*; import org.springframework.boot.test.mock.mockito.*; import static org.assertj.core.api.Assertions.*; import static org.mockito.BDDMockito.*; import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.*; import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.*; @RunWith(SpringRunner.class) @WebMvcTest(UserVehicleController.class) public class MyControllerTests { @Autowired private MockMvc mvc; @MockBean private UserVehicleService userVehicleService; @Test public void testExample() throws Exception { given(this.userVehicleService.getVehicleDetails("sboot")) .willReturn(new VehicleDetails("Honda", "Civic")); this.mvc.perform(get("/sboot/vehicle").accept(MediaType.TEXT_PLAIN)) .andExpect(status().isOk()).andExpect(content().string("Honda Civic")); } }
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| If you need to configure elements of the auto-configuration (for example, when servlet filters should be applied) you can use attributes in the |
If you use HtmlUnit or Selenium, auto-configuration also provides an HTMLUnit WebClient bean and/or a WebDriver bean. The following example uses HtmlUnit:
import com.gargoylesoftware.htmlunit.*;
import org.junit.*; import org.junit.runner.*; import org.springframework.beans.factory.annotation.*; import org.springframework.boot.test.autoconfigure.web.servlet.*; import org.springframework.boot.test.mock.mockito.*; import static org.assertj.core.api.Assertions.*; import static org.mockito.BDDMockito.*; @RunWith(SpringRunner.class) @WebMvcTest(UserVehicleController.class) public class MyHtmlUnitTests { @Autowired private WebClient webClient; @MockBean private UserVehicleService userVehicleService; @Test public void testExample() throws Exception { given(this.userVehicleService.getVehicleDetails("sboot")) .willReturn(new VehicleDetails("Honda", "Civic")); HtmlPage page = this.webClient.getPage("/sboot/vehicle.html"); assertThat(page.getBody().getTextContent()).isEqualTo("Honda Civic"); } }
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| By default, Spring Boot puts |
A list of the auto-configuration settings that are enabled by @WebMvcTest can be found in the appendix.
To test that Spring WebFlux controllers are working as expected, you can use the @WebFluxTest annotation. @WebFluxTest auto-configures the Spring WebFlux infrastructure and limits scanned beans to @Controller, @ControllerAdvice, @JsonComponent, Converter, and WebFluxConfigurer. Regular @Componentbeans are not scanned when the @WebFluxTest annotation is used.
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| If you need to register extra components such as Jackson |
Often, @WebFluxTest is limited to a single controller and used in combination with the @MockBean annotation to provide mock implementations for required collaborators.
@WebFluxTest also auto-configures WebTestClient, which offers a powerful way to quickly test WebFlux controllers without needing to start a full HTTP server.
|
| You can also auto-configure |
import org.junit.Test;
import org.junit.runner.RunWith; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.test.autoconfigure.web.reactive.WebFluxTest; import org.springframework.http.MediaType; import org.springframework.test.context.junit4.SpringRunner; import org.springframework.test.web.reactive.server.WebTestClient; @RunWith(SpringRunner.class) @WebFluxTest(UserVehicleController.class) public class MyControllerTests { @Autowired private WebTestClient webClient; @MockBean private UserVehicleService userVehicleService; @Test public void testExample() throws Exception { given(this.userVehicleService.getVehicleDetails("sboot")) .willReturn(new VehicleDetails("Honda", "Civic")); this.webClient.get().uri("/sboot/vehicle").accept(MediaType.TEXT_PLAIN) .exchange() .expectStatus().isOk() .expectBody(String.class).isEqualTo("Honda Civic"); } }
A list of the auto-configuration that is enabled by @WebFluxTest can be found in the appendix.
You can use the @DataJpaTest annotation to test JPA applications. By default, it configures an in-memory embedded database, scans for @Entity classes, and configures Spring Data JPA repositories. Regular @Component beans are not loaded into the ApplicationContext.
By default, data JPA tests are transactional and roll back at the end of each test. See the relevant section in the Spring Framework Reference Documentation for more details. If that is not what you want, you can disable transaction management for a test or for the whole class as follows:
import org.junit.Test;
import org.junit.runner.RunWith; import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest; import org.springframework.test.context.junit4.SpringRunner; import org.springframework.transaction.annotation.Propagation; import org.springframework.transaction.annotation.Transactional; @RunWith(SpringRunner.class) @DataJpaTest @Transactional(propagation = Propagation.NOT_SUPPORTED) public class ExampleNonTransactionalTests { }
Data JPA tests may also inject a TestEntityManager bean, which provides an alternative to the standard JPA EntityManager that is specifically designed for tests. If you want to use TestEntityManager outside of @DataJpaTest instances, you can also use the @AutoConfigureTestEntityManager annotation. A JdbcTemplateis also available if you need that. The following example shows the `@DataJpaTest`annotation in use:
import org.junit.*;
import org.junit.runner.*; import org.springframework.boot.test.autoconfigure.orm.jpa.*; import static org.assertj.core.api.Assertions.*; @RunWith(SpringRunner.class) @DataJpaTest public class ExampleRepositoryTests { @Autowired private TestEntityManager entityManager; @Autowired private UserRepository repository; @Test public void testExample() throws Exception { this.entityManager.persist(new User("sboot", "1234")); User user = this.repository.findByUsername("sboot"); assertThat(user.getUsername()).isEqualTo("sboot"); assertThat(user.getVin()).isEqualTo("1234"); } }
In-memory embedded databases generally work well for tests, since they are fast and do not require any installation. If, however, you prefer to run tests against a real database you can use the @AutoConfigureTestDatabase annotation, as shown in the following example:
@RunWith(SpringRunner.class) @DataJpaTest @AutoConfigureTestDatabase(replace=Replace.NONE) public class ExampleRepositoryTests { // ... }
A list of the auto-configuration settings that are enabled by @DataJpaTest can be found in the appendix.
@JdbcTest is similar to @DataJpaTest but for pure JDBC-related tests. By default, it also configures an in-memory embedded database and a JdbcTemplate. Regular @Component beans are not loaded into the ApplicationContext.
By default, JDBC tests are transactional and roll back at the end of each test. See the relevant section in the Spring Framework Reference Documentation for more details. If that is not what you want, you can disable transaction management for a test or for the whole class as follows:
import org.junit.Test;
import org.junit.runner.RunWith; import org.springframework.boot.test.autoconfigure.jdbc.JdbcTest; import org.springframework.test.context.junit4.SpringRunner; import org.springframework.transaction.annotation.Propagation; import org.springframework.transaction.annotation.Transactional; @RunWith(SpringRunner.class) @JdbcTest @Transactional(propagation = Propagation.NOT_SUPPORTED) public class ExampleNonTransactionalTests { }
If you prefer your test to run against a real database, you can use the @AutoConfigureTestDatabase annotation in the same way as for DataJpaTest. (SeeSection 43.3.9, “Auto-configured Data JPA Tests”.)
A list of the auto-configuration that is enabled by @JdbcTest can be found in the appendix.
You can use @JooqTest in a similar fashion as @JdbcTest but for jOOQ-related tests. As jOOQ relies heavily on a Java-based schema that corresponds with the database schema, the existing DataSource is used. If you want to replace it with an in-memory database, you can use @AutoconfigureTestDatabase to override those settings.
@JooqTest configures a DSLContext. Regular @Component beans are not loaded into the ApplicationContext. The following example shows the @JooqTestannotation in use:
import org.jooq.DSLContext;
import org.junit.Test; import org.junit.runner.RunWith; import org.springframework.boot.test.autoconfigure.jooq.JooqTest; import org.springframework.test.context.junit4.SpringRunner; @RunWith(SpringRunner.class) @JooqTest public class ExampleJooqTests { @Autowired private DSLContext dslContext; }
JOOQ tests are transactional and roll back at the end of each test by default. If that is not what you want, you can disable transaction management for a test or for the whole test class as shown in the JDBC example.
A list of the auto-configuration that is enabled by @JooqTest can be found in the appendix.
You can use @DataMongoTest to test MongoDB applications. By default, it configures an in-memory embedded MongoDB (if available), configures a MongoTemplate, scans for @Document classes, and configures Spring Data MongoDB repositories. Regular @Component beans are not loaded into the ApplicationContext. The following class shows the @DataMongoTest annotation in use:
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.test.autoconfigure.data.mongo.DataMongoTest; import org.springframework.data.mongodb.core.MongoTemplate; import org.springframework.test.context.junit4.SpringRunner; @RunWith(SpringRunner.class) @DataMongoTest public class ExampleDataMongoTests { @Autowired private MongoTemplate mongoTemplate; // }
In-memory embedded MongoDB generally works well for tests, since it is fast and does not require any developer installation. If, however, you prefer to run tests against a real MongoDB server, you should exclude the embedded MongoDB auto-configuration, as shown in the following example:
import org.junit.runner.RunWith;
import org.springframework.boot.autoconfigure.mongo.embedded.EmbeddedMongoAutoConfiguration; import org.springframework.boot.test.autoconfigure.data.mongo.DataMongoTest; import org.springframework.test.context.junit4.SpringRunner; @RunWith(SpringRunner.class) @DataMongoTest(excludeAutoConfiguration = EmbeddedMongoAutoConfiguration.class) public class ExampleDataMongoNonEmbeddedTests { }
A list of the auto-configuration settings that are enabled by @DataMongoTest can be found in the appendix.
You can use @DataNeo4jTest to test Neo4j applications. By default, it uses an in-memory embedded Neo4j (if the embedded driver is available), scans for @NodeEntity classes, and configures Spring Data Neo4j repositories. Regular @Component beans are not loaded into the ApplicationContext:
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.test.autoconfigure.data.neo4j.DataNeo4jTest; import org.springframework.test.context.junit4.SpringRunner; @RunWith(SpringRunner.class) @DataNeo4jTest public class ExampleDataNeo4jTests { @Autowired private YourRepository repository; // }
By default, Data Neo4j tests are transactional and roll back at the end of each test. See the relevant section in the Spring Framework Reference Documentation for more details. If that is not what you want, you can disable transaction management for a test or for the whole class as follows:
import org.junit.Test;
import org.junit.runner.RunWith; import org.springframework.boot.test.autoconfigure.data.neo4j.DataNeo4jTest; import org.springframework.test.context.junit4.SpringRunner; import org.springframework.transaction.annotation.Propagation; import org.springframework.transaction.annotation.Transactional; @RunWith(SpringRunner.class) @DataNeo4jTest @Transactional(propagation = Propagation.NOT_SUPPORTED) public class ExampleNonTransactionalTests { }
A list of the auto-configuration settings that are enabled by @DataNeo4jTest can be found in the appendix.
You can use @DataRedisTest to test Redis applications. By default, it scans for @RedisHash classes and configures Spring Data Redis repositories. Regular @Component beans are not loaded into the ApplicationContext. The following example shows the @DataRedisTest annotation in use:
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.test.autoconfigure.data.redis.DataRedisTest; import org.springframework.test.context.junit4.SpringRunner; @RunWith(SpringRunner.class) @DataRedisTest public class ExampleDataRedisTests { @Autowired private YourRepository repository; // }
A list of the auto-configuration settings that are enabled by @DataRedisTest can be found in the appendix.
You can use @DataLdapTest to test LDAP applications. By default, it configures an in-memory embedded LDAP (if available), configures an LdapTemplate, scans for @Entry classes, and configures Spring Data LDAP repositories. Regular @Component beans are not loaded into the ApplicationContext. The following example shows the @DataLdapTest annotation in use:
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.test.autoconfigure.data.ldap.DataLdapTest; import org.springframework.ldap.core.LdapTemplate; import org.springframework.test.context.junit4.SpringRunner; @RunWith(SpringRunner.class) @DataLdapTest public class ExampleDataLdapTests { @Autowired private LdapTemplate ldapTemplate; // }
In-memory embedded LDAP generally works well for tests, since it is fast and does not require any developer installation. If, however, you prefer to run tests against a real LDAP server, you should exclude the embedded LDAP auto-configuration, as shown in the following example:
import org.junit.runner.RunWith;
import org.springframework.boot.autoconfigure.ldap.embedded.EmbeddedLdapAutoConfiguration; import org.springframework.boot.test.autoconfigure.data.ldap.DataLdapTest; import org.springframework.test.context.junit4.SpringRunner; @RunWith(SpringRunner.class) @DataLdapTest(excludeAutoConfiguration = EmbeddedLdapAutoConfiguration.class) public class ExampleDataLdapNonEmbeddedTests { }
A list of the auto-configuration settings that are enabled by @DataLdapTest can be found in the appendix.
You can use the @RestClientTest annotation to test REST clients. By default, it auto-configures Jackson, GSON, and Jsonb support, configures a RestTemplateBuilder, and adds support for MockRestServiceServer. The specific beans that you want to test should be specified by using the value or components attribute of @RestClientTest, as shown in the following example:
@RunWith(SpringRunner.class) @RestClientTest(RemoteVehicleDetailsService.class) public class ExampleRestClientTest { @Autowired private RemoteVehicleDetailsService service; @Autowired private MockRestServiceServer server; @Test public void getVehicleDetailsWhenResultIsSuccessShouldReturnDetails() throws Exception { this.server.expect(requestTo("/greet/details")) .andRespond(withSuccess("hello", MediaType.TEXT_PLAIN)); String greeting = this.service.callRestService(); assertThat(greeting).isEqualTo("hello"); } }
A list of the auto-configuration settings that are enabled by @RestClientTest can be found in the appendix.
You can use the @AutoConfigureRestDocs annotation to use Spring REST Docs in your tests with Mock MVC or REST Assured. It removes the need for the JUnit rule in Spring REST Docs.
@AutoConfigureRestDocs can be used to override the default output directory (target/generated-snippets if you are using Maven or build/generated-snippets if you are using Gradle). It can also be used to configure the host, scheme, and port that appears in any documented URIs.
@AutoConfigureRestDocs customizes the MockMvc bean to use Spring REST Docs. You can inject it by using @Autowired and use it in your tests as you normally would when using Mock MVC and Spring REST Docs, as shown in the following example:
import org.junit.Test;
import org.junit.runner.RunWith; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest; import org.springframework.http.MediaType; import org.springframework.test.context.junit4.SpringRunner; import org.springframework.test.web.servlet.MockMvc; import static org.springframework.restdocs.mockmvc.MockMvcRestDocumentation.document; import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get; import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.*; @RunWith(SpringRunner.class) @WebMvcTest(UserController.class) @AutoConfigureRestDocs public class UserDocumentationTests { @Autowired private MockMvc mvc; @Test public void listUsers() throws Exception { this.mvc.perform(get("/users").accept(MediaType.TEXT_PLAIN)) .andExpect(status().isOk()) .andDo(document("list-users")); } }
If you require more control over Spring REST Docs configuration than offered by the attributes of @AutoConfigureRestDocs, a RestDocsMockMvcConfigurationCustomizer bean can be used, as shown in the following example:
@TestConfiguration static class CustomizationConfiguration implements RestDocsMockMvcConfigurationCustomizer { @Override public void customize(MockMvcRestDocumentationConfigurer configurer) { configurer.snippets().withTemplateFormat(TemplateFormats.markdown()); } }
If you want to make use of Spring REST Docs support for a parameterized output directory, you can create a RestDocumentationResultHandler bean. The auto-configuration calls alwaysDo with this result handler, thereby causing each MockMvc call to automatically generate the default snippets. The following example shows aRestDocumentationResultHandler being defined:
@TestConfiguration static class ResultHandlerConfiguration { @Bean public RestDocumentationResultHandler restDocumentation() { return MockMvcRestDocumentation.document("{method-name}"); } }
@AutoConfigureRestDocs makes a RequestSpecification bean, preconfigured to use Spring REST Docs, available to your tests. You can inject it by using @Autowired and use it in your tests as you normally would when using REST Assured and Spring REST Docs, as shown in the following example:
import io.restassured.specification.RequestSpecification;
import org.junit.Test; import org.junit.runner.RunWith; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.test.autoconfigure.restdocs.AutoConfigureRestDocs; import org.springframework.boot.test.context.SpringBootTest; import org.springframework.boot.test.context.SpringBootTest.WebEnvironment; import org.springframework.boot.web.server.LocalServerPort; import org.springframework.test.context.junit4.SpringRunner; import static io.restassured.RestAssured.given; import static org.hamcrest.CoreMatchers.is; import static org.springframework.restdocs.restassured3.RestAssuredRestDocumentation.document; @RunWith(SpringRunner.class) @SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT) @AutoConfigureRestDocs public class UserDocumentationTests { @LocalServerPort private int port; @Autowired private RequestSpecification documentationSpec; @Test public void listUsers() throws Exception { given(this.documentationSpec).filter(document("list-users")).when() .port(this.port).get("/").then().assertThat().statusCode(is(200)); } }
If you require more control over Spring REST Docs configuration than offered by the attributes of @AutoConfigureRestDocs, a RestDocsRestAssuredConfigurationCustomizer bean can be used, as shown in the following example:
@TestConfiguration public static class CustomizationConfiguration implements RestDocsRestAssuredConfigurationCustomizer { @Override public void customize(RestAssuredRestDocumentationConfigurer configurer) { configurer.snippets().withTemplateFormat(TemplateFormats.markdown()); } }
If you structure your code in a sensible way, your @SpringBootApplication class is used by default as the configuration of your tests.
It then becomes important not to litter the application’s main class with configuration settings that are specific to a particular area of its functionality.
Assume that you are using Spring Batch and you rely on the auto-configuration for it. You could define your @SpringBootApplication as follows:
@SpringBootApplication @EnableBatchProcessing public class SampleApplication { ... }
Because this class is the source configuration for the test, any slice test actually tries to start Spring Batch, which is definitely not what you want to do. A recommended approach is to move that area-specific configuration to a separate @Configuration class at the same level as your application, as shown in the following example:
@Configuration @EnableBatchProcessing public class BatchConfiguration { ... }
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| Depending on the complexity of your application, you may either have a single |
Another source of confusion is classpath scanning. Assume that, while you structured your code in a sensible way, you need to scan an additional package. Your application may resemble the following code:
@SpringBootApplication @ComponentScan({ "com.example.app", "org.acme.another" }) public class SampleApplication { ... }
This effectively overrides the default component scan directive with the side effect of scanning those two packages regardless of the slice that you chose. For instance, a@DataJpaTest seems to suddenly scan components and user configurations of your application. Again, moving the custom directive to a separate class is a good way to fix this issue.
|
| If this is not an option for you, you can create a |
If you wish to use Spock to test a Spring Boot application, you should add a dependency on Spock’s spock-spring module to your application’s build. spock-springintegrates Spring’s test framework into Spock. It is recommended that you use Spock 1.1 or later to benefit from a number of improvements to Spock’s Spring Framework and Spring Boot integration. See the documentation for Spock’s Spring module for further details.
A few test utility classes that are generally useful when testing your application are packaged as part of spring-boot.
ConfigFileApplicationContextInitializer is an ApplicationContextInitializer that you can apply to your tests to load Spring Boot application.properties files. You can use it when you do not need the full set of features provided by @SpringBootTest.
@ContextConfiguration(classes = Config.class,
initializers = ConfigFileApplicationContextInitializer.class)
|
| Using |
EnvironmentTestUtils lets you quickly add properties to a ConfigurableEnvironment or ConfigurableApplicationContext. You can call it with key=valuestrings, as follows:
EnvironmentTestUtils.addEnvironment(env, "org=Spring", "name=Boot");
OutputCapture is a JUnit Rule that you can use to capture System.out and System.err output. You can declare the capture as a @Rule and then use toString() for assertions, as follows:
import org.junit.Rule;
import org.junit.Test; import org.springframework.boot.test.rule.OutputCapture; import static org.hamcrest.Matchers.*; import static org.junit.Assert.*; public class MyTest { @Rule public OutputCapture capture = new OutputCapture(); @Test public void testName() throws Exception { System.out.println("Hello World!"); assertThat(capture.toString(), containsString("World")); } }
TestRestTemplate is a convenience alternative to Spring’s RestTemplate that is useful in integration tests. You can get a vanilla template or one that sends Basic HTTP authentication (with a username and password). In either case, the template behaves in a test-friendly way by not throwing exceptions on server-side errors. It is recommended, but not mandatory, to use the Apache HTTP Client (version 4.3.2 or better). If you have that on your classpath, the TestRestTemplate responds by configuring the client appropriately. If you do use Apache’s HTTP client, some additional test-friendly features are enabled:
- Redirects are not followed (so you can assert the response location).
- Cookies are ignored (so the template is stateless).
TestRestTemplate can be instantiated directly in your integration tests, as shown in the following example:
public class MyTest { private TestRestTemplate template = new TestRestTemplate(); @Test public void testRequest() throws Exception { HttpHeaders headers = template.getForEntity("http://myhost.com/example", String.class).getHeaders(); assertThat(headers.getLocation().toString(), containsString("myotherhost")); } }
Alternatively, if you use the @SpringBootTest annotation with WebEnvironment.RANDOM_PORT or WebEnvironment.DEFINED_PORT, you can just inject a fully configured TestRestTemplate and start using it. If necessary, additional customizations can be applied through the RestTemplateBuilder bean. Any URLs that do not specify a host and port automatically connect to the embedded server, as shown in the following example:
@RunWith(SpringRunner.class) @SpringBootTest public class MyTest { @Autowired private TestRestTemplate template; @Test public void testRequest() throws Exception { HttpHeaders headers = template.getForEntity("/example", String.class).getHeaders(); assertThat(headers.getLocation().toString(), containsString("myotherhost")); } @TestConfiguration static class Config { @Bean public RestTemplateBuilder restTemplateBuilder() { return new RestTemplateBuilder() .additionalMessageConverters(...) .customizers(...); } } }
Spring Boot provides WebSockets auto-configuration for embedded Tomcat 8.5, Jetty 9, and Undertow. If you deploy a war file to a standalone container, Spring Boot assumes that the container is responsible for the configuration of its WebSocket support.
Spring Framework provides rich WebSocket support that can be easily accessed through the spring-boot-starter-websocket module.
Spring Boot provides Web Services auto-configuration so that all you must do is define your Endpoints.
The Spring Web Services features can be easily accessed with the spring-boot-starter-webservices module.
SimpleWsdl11Definition and SimpleXsdSchema beans can be automatically created for your WSDLs and XSDs respectively. To do so, configure their location, as shown in the following example:
spring.webservices.wsdl-locations=classpath:/wsdl
If you work in a company that develops shared libraries, or if you work on an open-source or commercial library, you might want to develop your own auto-configuration. Auto-configuration classes can be bundled in external jars and still be picked-up by Spring Boot.
Auto-configuration can be associated to a "starter" that provides the auto-configuration code as well as the typical libraries that you would use with it. We first cover what you need to know to build your own auto-configuration and then we move on to the typical steps required to create a custom starter.
|
| A demo project is available to showcase how you can create a starter step-by-step. |
Under the hood, auto-configuration is implemented with standard @Configuration classes. Additional @Conditional annotations are used to constrain when the auto-configuration should apply. Usually, auto-configuration classes use @ConditionalOnClass and @ConditionalOnMissingBean annotations. This ensures that auto-configuration applies only when relevant classes are found and when you have not declared your own @Configuration.
You can browse the source code of spring-boot-autoconfigure to see the @Configuration classes that we provide (see the META-INF/spring.factories file).
Spring Boot checks for the presence of a META-INF/spring.factories file within your published jar. The file should list your configuration classes under theEnableAutoConfiguration key, as shown in the following example:
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\ com.mycorp.libx.autoconfigure.LibXAutoConfiguration,\ com.mycorp.libx.autoconfigure.LibXWebAutoConfiguration
You can use the @AutoConfigureAfter or @AutoConfigureBefore annotations if your configuration needs to be applied in a specific order. For example, if you provide web-specific configuration, your class may need to be applied after WebMvcAutoConfiguration.
If you want to order certain auto-configurations that should not have any direct knowledge of each other, you can also use @AutoConfigureOrder. That annotation has the same semantic as the regular @Order annotation but provides a dedicated order for auto-configuration classes.
|
| Auto-configurations must be loaded that way only. Make sure that they are defined in a specific package space and that, in particular, they are never the target of component scanning. |
You almost always want to include one or more @Conditional annotations on your auto-configuration class. The @ConditionalOnMissingBean annotation is one common example that is used to allow developers to ‘override’ auto-configuration if they are not happy with your defaults.
Spring Boot includes a number of @Conditional annotations that you can reuse in your own code by annotating @Configuration classes or individual @Beanmethods. These annotations include:
The @ConditionalOnClass and @ConditionalOnMissingClass annotations let configuration be included based on the presence or absence of specific classes. Due to the fact that annotation metadata is parsed by using ASM, you can use the value attribute to refer to the real class, even though that class might not actually appear on the running application classpath. You can also use the name attribute if you prefer to specify the class name by using a String value.
|
| If you use |
The @ConditionalOnBean and @ConditionalOnMissingBean annotations let a bean be included based on the presence or absence of specific beans. You can use the value attribute to specify beans by type or name to specify beans by name. The search attribute lets you limit the ApplicationContext hierarchy that should be considered when searching for beans.
When placed on a @Bean method, the target type defaults to the return type of the method, as shown in the following example:
@Configuration public class MyAutoConfiguration { @Bean @ConditionalOnMissingBean public MyService myService() { ... } }
In the preceding example, the myService bean is going to be created if no bean of type MyService is already contained in the ApplicationContext.
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| You need to be very careful about the order that bean definitions are added as these conditions are evaluated based on what has been processed so far. For this reason, we recommend only using |
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The @ConditionalOnProperty annotation lets configuration be included based on a Spring Environment property. Use the prefix and name attributes to specify the property that should be checked. By default, any property that exists and is not equal to false is matched. You can also create more advanced checks by using the havingValue and matchIfMissing attributes.
The @ConditionalOnResource annotation lets configuration be included only when a specific resource is present. Resources can be specified by using the usual Spring conventions, as shown in the following example: file:/home/user/test.dat.
The @ConditionalOnWebApplication and @ConditionalOnNotWebApplication annotations let configuration be included depending on whether the application is a 'web application'. A web application is any application that is using a Spring WebApplicationContext, defines a session scope, or has a StandardServletEnvironment.
The @ConditionalOnExpression annotation lets configuration be included based on the result of a SpEL expression.
A full Spring Boot starter for a library may contain the following components:
- The
autoconfiguremodule that contains the auto-configuration code. - The
startermodule that provides a dependency to theautoconfiguremodule as well as the library and any additional dependencies that are typically useful. In a nutshell, adding the starter should provide everything needed to start using that library.
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| You may combine the auto-configuration code and the dependency management in a single module if you do not need to separate those two concerns. |
You should make sure to provide a proper namespace for your starter. Do not start your module names with spring-boot, even if you are using a different Maven groupId. We may offer official support for the thing you auto-configure in the future.
As a rule of thumb, you should name a combined module after the starter. For example, assume that you are creating a starter for "acme" and that you name the auto-configure module acme-spring-boot-autoconfigure and the starter acme-spring-boot-starter. If you only have one module that combines the two, name it acme-spring-boot-starter.
Also, if your starter provides configuration keys, use a proper (that is, unique) namespace for them. In particular, do not include your keys in the namespaces that Spring Boot uses (such as server, management, spring, and so on). If you use the same namespace, we may modify these namespaces in the future in ways that break your modules.
Make sure to trigger meta-data generation so that IDE assistance is available for your keys as well. You may want to review the generated meta-data (META-INF/spring-configuration-metadata.json) to make sure your keys are properly documented.
The autoconfigure module contains everything that is necessary to get started with the library. It may also contain configuration key definitions (such as@ConfigurationProperties) and any callback interface that can be used to further customize how the components are initialized.
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| You should mark the dependencies to the library as optional so that you can include the |
The starter is really an empty jar. Its only purpose is to provide the necessary dependencies to work with the library. You can think of it as an opinionated view of what is required to get started.
Do not make assumptions about the project in which your starter is added. If the library you are auto-configuring typically requires other starters, mention them as well. Providing a proper set of default dependencies may be hard if the number of optional dependencies is high, as you should avoid including dependencies that are unnecessary for a typical usage of the library. In other words, you should not include optional dependencies.
If you want to learn more about any of the classes discussed in this section, you can check out the Spring Boot API documentation or you can browse the source code directly. If you have specific questions, take a look at the how-to section.
If you are comfortable with Spring Boot’s core features, you can continue on and read about production-ready features.
Spring Boot includes a number of additional features to help you monitor and manage your application when you push it to production. You can choose to manage and monitor your application by using HTTP endpoints or with JMX. Auditing, health, and metrics gathering can also be automatically applied to your application.
The spring-boot-actuator module provides all of Spring Boot’s production-ready features. The simplest way to enable the features is to add a dependency to the spring-boot-starter-actuator ‘Starter’.
To add the actuator to a Maven based project, add the following ‘Starter’ dependency:
<dependencies>
<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-actuator</artifactId> </dependency> </dependencies>
For Gradle, use the following declaration:
dependencies {
compile("org.springframework.boot:spring-boot-starter-actuator")
}
Actuator endpoints let you monitor and interact with your application. Spring Boot includes a number of built-in endpoints and lets you add your own. For example, thehealth endpoint provides basic application health information.
The way that endpoints are exposed depends on the type of technology that you choose. Most applications choose HTTP monitoring, where the ID of the endpoint along with a prefix of /application is mapped to a URL. For example, by default, the health endpoint is mapped to /application/health.
The following technology-agnostic endpoints are available:
| ID | Description |
|---|---|
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Exposes audit events information for the current application. |
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Showing the conditions that were evaluated on configuration and auto-configuration classes and the reasons why they did or did not match. |
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Displays a complete list of all the Spring beans in your application. |
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Displays a collated list of all |
|
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Exposes properties from Spring’s |
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Shows any Flyway database migrations that have been applied. |
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Shows application health information. |
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Displays arbitrary application info. |
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|
Shows and modifies the configuration of loggers in the application. |
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Shows any Liquibase database migrations that have been applied. |
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Shows ‘metrics’ information for the current application. |
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Displays a collated list of all |
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|
Displays the scheduled tasks in your application. |
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|
Allows retrieval and deletion of user sessions from a Spring Session-backed session store. Not available when using Spring Session’s support for reactive web applications. |
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Lets the application be gracefully shutdown (not enabled by default). |
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|
Shows application status information (that is, |
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Performs a thread dump. |
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Displays trace information (by default, the last 100 HTTP requests). |
If your application is a web application (Spring MVC, Spring WebFlux, or Jersey), you can use the following additional endpoints:
| ID | Description |
|---|---|
|
|
Returns a GZip compressed |
|
|
Returns the contents of the logfile (if |
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|
Exposes metrics in a format that can be scraped by a Prometheus server. |
To learn more about the Actuator’s endpoints and their request and response formats, please refer to the separate API documentation that is available in the following formats:
Since Endpoints may contain sensitive information, careful consideration should be given about when to expose them. Out of the box, Spring Boot will expose all enabled endpoints over JMX, but only the health and info endpoints over HTTP.
To change the endpoints that are exposed you can use the expose and exclude property for the technology. For example, to only expose the health over JMX you would use:
application.properties.
management.endpoints.jmx.expose=health
The * character can be used to indicate all endpoints. For example, to expose everything over HTTP except the env endpoint you would use:
application.properties.
management.endpoints.web.expose=*
management.endpoints.web.exclude=env
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| If your application is exposed publicly we strongly recommend that you also secure your endpoints. |
|
| If you want to implement your own strategy for when endpoints are exposed you can register an |
You should take care to secure HTTP endpoints in the same way that you would any other sensitive URL. Spring Boot will not apply any security on your behalf, however, it does provide some convenient `RequestMatcher`s that can be used in combination with Spring Security.
A typical Spring Security configuration could look something like this:
@Configuration public class ActuatorSecurity extends WebSecurityConfigurerAdapter { @Override protected void configure(HttpSecurity http) throws Exception { http.requestMatcher(EndpointRequest.toAnyEndpoint()).authorizeRequests() .anyRequest().hasRole("ENDPOINT_ADMIN") .and() .httpBasic(); } }
The above uses EndpointRequest.toAnyEndpoint() to match a request to any endpoint, then ensure that all have the ENDPOINT_ADMIN role. Several other matcher methods are also available on EndpointRequest (see the API documentation for details).
If you deploy applications behind a firewall, you may prefer that all your actuator endpoints can be accessed without requiring authentication. You can do so by changing the management.endpoints.web.expose property, as follows:
application.properties.
management.endpoints.web.expose=*
Endpoints can be customized by using Spring properties. You can change whether an endpoint is enabled and the amount of time it will cache responses.
For example, the following application.properties changes the time-to-live of the beans endpoint and also enables shutdown:
management.endpoint.beans.cache.time-to-live=10
management.endpoint.shutdown.enabled=true
|
| The prefix |
By default, all endpoints except for shutdown are enabled. If you prefer to specifically “opt-in” endpoint enablement, you can use themanagement.endpoints.enabled-by-default property. For example, the following settings disable all endpoints except for info:
management.endpoints.enabled-by-default=false
management.endpoint.info.enabled=true
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| Disabled endpoints are removed entirely from the |
A “discovery page” is added with links to all the endpoints. The “discovery page” is available on /application by default.
When a custom management context path is configured, the “discovery page” automatically moves from /application to the root of the management context. For example, if the management context path is /management, then the discovery page is available from /management. When the management context path is set to /, the discovery page is disabled to prevent the possibility of a clash with other mappings.
By default, endpoints are exposed over HTTP under the /application path using ID of the endpoint. For example, the beans endpoint is exposed under /application/beans. If you want to map endpoints to a different path you can use the management.endpoints.web.path-mapping property. You can also usemanagement.endpoints.web.base-path if you want change the base path.
Here’s an example that remaps /application/health to /healthcheck:
application.properties.
management.endpoints.web.base-path=/
management.endpoints.path-mapping.health=healthcheck
Cross-origin resource sharing (CORS) is a W3C specification that allows you to specify in a flexible way what kind of cross domain requests are authorized. If you use Spring MVC or Spring WebFlux, Actuator’s web endpoints can be configured to support such scenarios.
CORS support is disabled by default and is only enabled once the management.endpoints.web.cors.allowed-origins property has been set. The following configuration permits GET and POST calls from the example.com domain:
management.endpoints.web.cors.allowed-origins=http://example.com
management.endpoints.web.cors.allowed-methods=GET,POST
|
| See CorsEndpointProperties for a complete list of options. |
If you add a @Bean annotated with @Endpoint, any methods annotated with @ReadOperation, @WriteOperation or @DeleteOperation are automatically exposed over JMX and, in a web application, over HTTP as well.
You can also write technology specific endpoints by using @JmxEndpoint or @WebEndpoint. These endpoints are filtered to their respective technologies. For example, @WebEndpoint will be exposed only over HTTP and not over JMX.
Finally, it’s possible to write technology specific extensions using @EndpointWebExtension and @EndpointJmxExtension. These annotations allow you to provide technology specific operations to augment an existing endpoint.
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| If you add endpoints as a library feature, consider adding a configuration class annotated with |
You can use health information to check the status of your running application. It is often used by monitoring software to alert someone when a production system goes down. The default information exposed by the health endpoint depends on how it is accessed. For an unauthenticated connection in a secure application, a simple ‘status’ message is returned. For an authenticated connection, additional details are also displayed. (See Section 50.6, “HTTP Health Endpoint Format and Access Restrictions” for HTTP details.)
Health information is collected from all HealthIndicator beans defined in your ApplicationContext. Spring Boot includes a number of auto-configuredHealthIndicators, and you can also write your own. By default, the final system state is derived by the HealthAggregator, which sorts the statuses from eachHealthIndicator based on an ordered list of statuses. The first status in the sorted list is used as the overall health status. If no HealthIndicator returns a status that is known to the HealthAggregator, an UNKNOWN status is used.
The following HealthIndicators are auto-configured by Spring Boot when appropriate:
| Name | Description |
|---|---|
| Checks that a Cassandra database is up. |
|
| Checks for low disk space. |
|
| Checks that a connection to |
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| Checks that an Elasticsearch cluster is up. |
|
| Checks that a JMS broker is up. |
|
| Checks that a mail server is up. |
|
| Checks that a Mongo database is up. |
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| Checks that a Rabbit server is up. |
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| Checks that a Redis server is up. |
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| Checks that a Solr server is up. |
|
| It is possible to disable them all using the |
To provide custom health information, you can register Spring beans that implement the HealthIndicator interface. You need to provide an implementation of the health() method and return a Health response. The Health response should include a status and can optionally include additional details to be displayed. The following code shows a sample HealthIndicator implementation:
import org.springframework.boot.actuate.health.Health;
import org.springframework.boot.actuate.health.HealthIndicator; import org.springframework.stereotype.Component; @Component public class MyHealthIndicator implements HealthIndicator { @Override public Health health() { int errorCode = check(); // perform some specific health check if (errorCode != 0) { return Health.down().withDetail("Error Code", errorCode).build(); } return Health.up().build(); } }
|
| The identifier for a given |
In addition to Spring Boot’s predefined Status types, it is also possible for Health to return a custom Status that represents a new system state. In such cases, a custom implementation of the HealthAggregator interface also needs to be provided, or the default implementation has to be configured by using the management.health.status.order configuration property.
For example, assume a new Status with code FATAL is being used in one of your HealthIndicator implementations. To configure the severity order, add the following to your application properties:
management.health.status.order=FATAL, DOWN, OUT_OF_SERVICE, UNKNOWN, UP
The HTTP status code in the response reflects the overall health status (for example, UP maps to 200, while OUT_OF_SERVICE and DOWN map to 503). You might also want to register custom status mappings if you access the health endpoint over HTTP. For example, the following property maps FATAL to 503 (service unavailable):
management.health.status.http-mapping.FATAL=503
|
| If you need more control, you can define your own |
The following table shows the default status mappings for the built-in statuses:
| Status | Mapping |
|---|---|
| DOWN |
SERVICE_UNAVAILABLE (503) |
| OUT_OF_SERVICE |
SERVICE_UNAVAILABLE (503) |
| UP |
No mapping by default, so http status is 200 |
| UNKNOWN |
No mapping by default, so http status is 200 |
Application information exposes various information collected from all InfoContributor beans defined in your ApplicationContext. Spring Boot includes a number of auto-configured InfoContributors, and you can write your own.
The following InfoContributors are auto-configured by Spring Boot, when appropriate:
| Name | Description |
|---|---|
| Expose any key from the |
|
| Expose git information if a |
|
| Expose build information if a |
|
| It is possible to disable them all using the |
You can customize the data exposed by the info endpoint by setting info.* Spring properties. All Environment properties under the info key are automatically exposed. For example, you could add the following settings to your application.properties file:
info.app.encoding=UTF-8
info.app.java.source=1.8 info.app.java.target=1.8
|
| Rather than hardcoding those values, you could also expand info properties at build time. Assuming you use Maven, you could rewrite the preceding example as follows: info.app.encoding=@project.build.sourceEncoding@
info.app.java.source=@java.version@ info.app.java.target=@java.version@ |
Another useful feature of the info endpoint is its ability to publish information about the state of your git source code repository when the project was built. If aGitProperties bean is available, the git.branch, git.commit.id and git.commit.time properties are exposed.
|
| A |
If you want to display the full git information (that is, the full content of git.properties), use the management.info.git.mode property, as follows:
management.info.git.mode=full
If a BuildProperties bean is available, the info endpoint can also publish information about your build. This happens if a META-INF/build-info.properties file is available in the classpath.
|
| The Maven and Gradle plugins can both generate that file. See "Generate build information" for more details. |
To provide custom application information, you can register Spring beans that implement the InfoContributor interface.
The following example contributes an example entry with a single value:
import java.util.Collections;
import org.springframework.boot.actuate.info.Info; import org.springframework.boot.actuate.info.InfoContributor; import org.springframework.stereotype.Component; @Component public class ExampleInfoContributor implements InfoContributor { @Override public void contribute(Info.Builder builder) { builder.withDetail("example", Collections.singletonMap("key", "value")); } }
If you reach the info endpoint, you should see a response that contains the following additional entry:
{
"example": { "key" : "value" } }
If you are developing a Spring MVC application, Spring Boot Actuator auto-configures all enabled endpoints to be exposed over HTTP. The default convention is to use the id of the endpoint with a prefix of /application as the URL path. For example, health is exposed as /application/health.
Sometimes, it is useful to customize the prefix for the management endpoints. For example, your application might already use /application for another purpose. You can use the management.endpoints.web.base-path property to change the prefix for your management endpoint, as shown in the following example:
management.endpoints.web.base-path=/manage
The preceding application.properties example changes the endpoint from /application/{id} to /manage/{id} (e.g. /manage/info).
|
| Unless the management port has been configured to expose endpoints using a different HTTP port, |
Exposing management endpoints by using the default HTTP port is a sensible choice for cloud based deployments. If, however, your application runs inside your own data center, you may prefer to expose endpoints by using a different HTTP port.
You can set the management.server.port property to change the HTTP port, as shown in the following example:
management.server.port=8081
Since your management port is often protected by a firewall and not exposed to the public, you might not need security on the management endpoints, even if your main application is secure. In that case, you should have Spring Security on the classpath, and you can disable management security as follows:
management.security.enabled=false
(If you do not have Spring Security on the classpath, there is no need to explicitly disable the management security in this way. Doing so might even break the application.)
When configured to use a custom port, the management server can also be configured with its own SSL by using the various management.server.ssl.* properties. For example, doing so lets a management server be available via HTTP while the main application uses HTTPS, as shown in the following property settings:
server.port=8443
server.ssl.enabled=true server.ssl.key-store=classpath:store.jks server.ssl.key-password=secret management.server.port=8080 management.server.ssl.enabled=false
Alternatively, both the main server and the management server can use SSL but with different key stores, as follows:
server.port=8443
server.ssl.enabled=true server.ssl.key-store=classpath:main.jks server.ssl.key-password=secret management.server.port=8080 management.server.ssl.enabled=true management.server.ssl.key-store=classpath:management.jks management.server.ssl.key-password=secret
You can customize the address that the management endpoints are available on by setting the management.server.address property. Doing so can be useful if you want to listen only on an internal or ops-facing network or to listen only for connections from localhost.
|
| You can only listen on a different address if the port is different from the main server port. |
The following example application.properties does not allow remote management connections:
management.server.port=8081
management.server.address=127.0.0.1
If you do not want to expose endpoints over HTTP, you can set the management port to -1, as shown in the following example:
management.server.port=-1
The information exposed by the health endpoint varies, depending on whether it is accessed anonymously and whether the enclosing application is secure. By default, when accessed anonymously in a secure application, any details about the server’s health are hidden and the endpoint indicates whether the server is up or down.
The following example shows a summarized HTTP response (default for anonymous request):
$ curl -i localhost:8080/health
HTTP/1.1 200
X-Application-Context: application
Content-Type: application/vnd.spring-boot.actuator.v2+json;charset=UTF-8
Content-Length: 15
{"status":"UP"}
The following example shows a summarized HTTP response for status "DOWN" (notice the 503 status code):
$ curl -i localhost:8080/health
HTTP/1.1 503
X-Application-Context: application
Content-Type: application/vnd.spring-boot.actuator.v2+json;charset=UTF-8
Content-Length: 17
{"status":"DOWN"}
The following example shows a detailed HTTP response:
$ curl -i localhost:8080/health
HTTP/1.1 200 OK
X-Application-Context: application
Content-Type: application/vnd.spring-boot.actuator.v2+json;charset=UTF-8
Content-Length: 221
{
"status" : "UP",
"diskSpace" : {
"status" : "UP",
"total" : 63251804160,
"free" : 31316164608,
"threshold" : 10485760
},
"db" : {
"status" : "UP",
"database" : "H2",
"hello" : 1
}
}
Java Management Extensions (JMX) provide a standard mechanism to monitor and manage applications. By default, Spring Boot exposes management endpoints as JMX MBeans under the org.springframework.boot domain.
The name of the MBean is usually generated from the id of the endpoint. For example the health endpoint is exposed as org.springframework.boot:type=Endpoint,name=Health.
If your application contains more than one Spring ApplicationContext, you may find that names clash. To solve this problem, you can set themanagement.endpoints.jmx.unique-names property to true so that MBean names are always unique.
You can also customize the JMX domain under which endpoints are exposed. The following settings show an example of doing so in application.properties:
management.endpoints.jmx.domain=com.example.myapp
management.endpoints.jmx.unique-names=true
If you do not want to expose endpoints over JMX, you can set the endpoints.default.jmx.enabled property to false, as shown in the following example:
endpoints.default.jmx.enabled=false
Jolokia is a JMX-HTTP bridge that provides an alternative method of accessing JMX beans. To use Jolokia, include a dependency to org.jolokia:jolokia-core. For example, with Maven, you would add the following dependency:
<dependency>
<groupId>org.jolokia</groupId> <artifactId>jolokia-core</artifactId> </dependency>
Jolokia can then be accessed by using /application/jolokia on your management HTTP server.
Jolokia has a number of settings that you would traditionally configure using servlet parameters. With Spring Boot, you can use your application.properties. Prefix the parameter with management.jolokia.config., as shown in the following example:
management.jolokia.config.debug=true
Spring Boot Actuator includes the ability to view and configure the log levels of your application at runtime. You can view either the entire list or an individual logger’s configuration, which is made up of both the explicitly configured logging level as well as the effective logging level given to it by the logging framework. These levels can be one of:
TRACEDEBUGINFOWARNERRORFATALOFFnull
null indicates that there is no explicit configuration.
In order to configure a given logger, you POST a partial entity to the resource’s URI, as shown in the following example:
{
"configuredLevel": "DEBUG" }
|
| To "reset" the specific level of the logger (and use the default configuration instead), you can pass a value of |
Spring Boot Actuator provides dependency management and auto-configuration for Micrometer, an application metrics facade that supports numerous monitoring systems:
Micrometer provides a separate module for each supported monitoring system. Depending on one (or more) of these modules is sufficient to get started with Micrometer in your Spring Boot application. To learn more about Micrometer’s capabilities, please refer to its reference documentation.
Auto-configuration enables the instrumentation of requests handled by Spring MVC. When spring.metrics.web.server.auto-time-requests is true, this instrumentation occurs for all requests. Alternatively, when set to false, you can enable instrumentation by adding @Timed to a request-handling method.
By default, metrics are generated with the name, http.server.requests. The name can be customized by setting the spring.metrics.web.server.requests-metrics-name property.
By default, Spring MVC-related metrics are tagged with the following information:
- The request’s method.
- The request’s URI (templated if possible).
- The simple class name of any exception that was thrown while handling the request.
- The response’s status.
To customize the tags, provide a @Bean that implements WebMvcTagsProvider.
Auto-configuration enables the instrumentation of all requests handled by WebFlux controllers. You can also use a helper class, RouterFunctionMetrics, to instrument applications that use WebFlux’s functional programming model.
By default, metrics are generated with the name http.server.requests. You can customize the name by setting the spring.metrics.web.server.requests-metrics-name property.
By default, WebFlux-related metrics for the annotation-based programming model are tagged with the following information:
- The request’s method.
- The request’s URI (templated if possible).
- The simple class name of any exception that was thrown while handling the request.
- The response’s status.
To customize the tags, provide a @Bean that implements WebFluxTagsProvider.
By default, metrics for the functional programming model are tagged with the following information:
- The request’s method
- The request’s URI (templated if possible).
- The response’s status.
To customize the tags, use the defaultTags method on your RouterFunctionMetrics instance.
Auto-configuration customizes the auto-configured RestTemplate to enable the instrumentation of its requests. MetricsRestTemplateCustomizer can be used to customize your own RestTemplate instances.
By default, metrics are generated with the name, http.client.requests. The name can be customized by setting the spring.metrics.web.client.requests-metrics-name property.
Auto-configuration will enable the instrumentation of all available DataSources with a metric named data.source. Data source instrumentation results in gauges representing the currently active, maximum allowed, and minimum allowed connections in the pool. Each of these gauges has a name which is prefixed by data.source by default. The prefix can be customized by using the spring.metrics.jdbc.datasource-metric-name property.
Metrics will also be tagged by the name of the DataSource computed based on the bean name.
Auto-configuration enables binding of a number of Spring Integration-related metrics:
Table 53.1. General metrics
| Metric | Description |
|---|---|
|
|
Number of Spring Integration channels |
|
|
Number of Spring Integration handlers |
|
|
Number of Spring Integration sources |
Table 53.2. Channel metrics
| Metric | Description |
|---|---|
|
|
Number of receives |
|
|
Number of failed sends |
|
|
Number of successful sends |
Table 53.3. Handler metrics
| Metric | Description |
|---|---|
|
|
Maximum handler duration in milliseconds |
|
|
Minimum handler duration in milliseconds |
|
|
Mean handler duration in milliseconds |
|
|
Number of active handlers |
Once Spring Security is in play Spring Boot Actuator has a flexible audit framework that publishes events (by default, ‘authentication success’, ‘failure’ and ‘access denied’ exceptions). This feature can be very useful for reporting and for implementing a lock-out policy based on authentication failures. To customize published security events, you can provide your own implementations of AbstractAuthenticationAuditListener and AbstractAuthorizationAuditListener.
You can also use the audit services for your own business events. To do so, either inject the existing AuditEventRepository into your own components and use that directly or publish an AuditApplicationEvent with the Spring ApplicationEventPublisher (by implementing ApplicationEventPublisherAware).
Tracing is automatically enabled for all HTTP requests. You can view the trace endpoint and obtain basic information about the last 100 requests. The following listing shows sample output:
[{
"timestamp": 1394343677415, "info": { "method": "GET", "path": "/trace", "headers": { "request": { "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8", "Connection": "keep-alive", "Accept-Encoding": "gzip, deflate", "User-Agent": "Mozilla/5.0 Gecko/Firefox", "Accept-Language": "en-US,en;q=0.5", "Cookie": "_ga=GA1.1.827067509.1390890128; ..." "Authorization": "Basic ...", "Host": "localhost:8080" }, "response": { "Strict-Transport-Security": "max-age=31536000 ; includeSubDomains", "X-Application-Context": "application:8080", "Content-Type": "application/json;charset=UTF-8", "status": "200" } } } },{ "timestamp": 1394343684465, ... }]
By default, the trace includes the following information:
| Name | Description |
|---|---|
| Request Headers |
Headers from the request. |
| Response Headers |
Headers from the response. |
| Cookies |
|
| Errors |
The error attributes (if any). |
| Time Taken |
The time taken to service the request in milliseconds. |
If you need to trace additional events, you can inject a TraceRepository into your Spring beans. The add method accepts a single Map structure that is converted to JSON and logged.
By default, an InMemoryTraceRepository that stores the last 100 events is used. If you need to expand the capacity, you can define your own instance of theInMemoryTraceRepository bean. You can also create your own alternative TraceRepository implementation.
In the spring-boot module, you can find two classes to create files that are often useful for process monitoring:
ApplicationPidFileWritercreates a file containing the application PID (by default, in the application directory with the file name,application.pid).EmbeddedServerPortFileWritercreates a file (or files) containing the ports of the embedded server (by default, in the application directory with the file nameapplication.port).
By default, these writers are not activated, but you can enable them in one of the ways described in the next section.
In the META-INF/spring.factories file, you can activate the listener(s) that writes a PID file, as shown in the following example:
org.springframework.context.ApplicationListener=\ org.springframework.boot.system.ApplicationPidFileWriter,\ org.springframework.boot.system.EmbeddedServerPortFileWriter
Spring Boot’s actuator module includes additional support that is activated when you deploy to a compatible Cloud Foundry instance. The /cloudfoundryapplicationpath provides an alternative secured route to all @Endpoint beans.
The extended support lets Cloud Foundry management UIs (such as the web application that you can use to view deployed applications) be augmented with Spring Boot actuator information. For example, an application status page may include full health information instead of the typical “running” or “stopped” status.
|
| The |
If you want to fully disable the /cloudfoundryapplication endpoints, you can add the following setting to your application.properties file:
application.properties.
management.cloudfoundry.enabled=false
By default, the security verification for /cloudfoundryapplication endpoints makes SSL calls to various Cloud Foundry services. If your Cloud Foundry UAA or Cloud Controller services use self-signed certificates, you need to set the following property:
application.properties.
management.cloudfoundry.skip-ssl-validation=true
If you define custom security configuration and you want extended Cloud Foundry actuator support, you should ensure that /cloudfoundryapplication/** paths are open. Without a direct open route, your Cloud Foundry application manager is not able to obtain endpoint data.
For Spring Security, you typically include something like mvcMatchers("/cloudfoundryapplication/**").permitAll() in your configuration, as shown in the following example:
@Override protected void configure(HttpSecurity http) throws Exception { http .authorizeRequests() .mvcMatchers("/cloudfoundryapplication/**") .permitAll() .mvcMatchers("/mypath") .hasAnyRole("SUPERUSER") .anyRequest() .authenticated().and() .httpBasic(); }
If you want to explore some of the concepts discussed in this chapter, you can take a look at the actuator sample applications. You also might want to read about graphing tools such as Graphite.
Otherwise, you can continue on, to read about ‘deployment options’ or jump ahead for some in-depth information about Spring Boot’s build tool plugins.
Spring Boot’s flexible packaging options provide a great deal of choice when it comes to deploying your application. You can deploy Spring Boot applications to a variety of cloud platforms, to container images (such as Docker), or to virtual/real machines.
This section covers some of the more common deployment scenarios.
Spring Boot’s executable jars are ready-made for most popular cloud PaaS (Platform-as-a-Service) providers. These providers tend to require that you “bring your own container”. They manage application processes (not Java applications specifically), so they need some intermediary layer that adapts your application to the cloud’s notion of a running process.
Two popular cloud providers, Heroku and Cloud Foundry, employ a “buildpack” approach. The buildpack wraps your deployed code in whatever is needed to start your application: it might be a JDK and a call to java, it might be an embedded web server, or it might be a full-fledged application server. A buildpack is pluggable, but ideally you should be able to get by with as few customizations to it as possible. This reduces the footprint of functionality that is not under your control. It minimizes divergence between development and production environments.
Ideally, your application, like a Spring Boot executable jar, has everything that it needs to run packaged within it.
In this section, we look at what it takes to get the simple application that we developed in the “Getting Started” section up and running in the Cloud.
Cloud Foundry provides default buildpacks that come into play if no other buildpack is specified. The Cloud Foundry Java buildpack has excellent support for Spring applications, including Spring Boot. You can deploy stand-alone executable jar applications as well as traditional .war packaged applications.
Once you have built your application (by using, for example, mvn clean package) and have installed the cf command line tool, deploy your application by using the cf push command, substituting the path to your compiled .jar. Be sure to have logged in with your cf command line client before pushing an application. The following line shows using the cf push command to deploy an application:
$ cf push acloudyspringtime -p target/demo-0.0.1-SNAPSHOT.jar
|
| In the preceding example, we substitute |
See the cf push documentation for more options. If there is a Cloud Foundry manifest.yml file present in the same directory, it is considered.
At this point, cf starts uploading your application, producing output similar to the following example:
Uploading acloudyspringtime... OK
Preparing to start acloudyspringtime... OK -----> Downloaded app package (8.9M) -----> Java Buildpack Version: v3.12 (offline) | https://github.com/cloudfoundry/java-buildpack.git#6f25b7e -----> Downloading Open Jdk JRE 1.8.0_121 from https://java-buildpack.cloudfoundry.org/openjdk/trusty/x86_64/openjdk-1.8.0_121.tar.gz (found in cache) Expanding Open Jdk JRE to .java-buildpack/open_jdk_jre (1.6s) -----> Downloading Open JDK Like Memory Calculator 2.0.2_RELEASE from https://java-buildpack.cloudfoundry.org/memory-calculator/trusty/x86_64/memory-calculator-2.0.2_RELEASE.tar.gz (found in cache) Memory Settings: -Xss349K -Xmx681574K -XX:MaxMetaspaceSize=104857K -Xms681574K -XX:MetaspaceSize=104857K -----> Downloading Container Certificate Trust Store 1.0.0_RELEASE from https://java-buildpack.cloudfoundry.org/container-certificate-trust-store/container-certificate-trust-store-1.0.0_RELEASE.jar (found in cache) Adding certificates to .java-buildpack/container_certificate_trust_store/truststore.jks (0.6s) -----> Downloading Spring Auto Reconfiguration 1.10.0_RELEASE from https://java-buildpack.cloudfoundry.org/auto-reconfiguration/auto-reconfiguration-1.10.0_RELEASE.jar (found in cache) Checking status of app 'acloudyspringtime'... 0 of 1 instances running (1 starting) ... 0 of 1 instances running (1 starting) ... 0 of 1 instances running (1 starting) ... 1 of 1 instances running (1 running) App started
Congratulations! The application is now live!
Once your application is live, you can verify the status of the deployed application by using the cf apps command, as shown in the following example:
$ cf apps Getting applications in ... OK name requested state instances memory disk urls ... acloudyspringtime started 1/1 512M 1G acloudyspringtime.cfapps.io ...
Once Cloud Foundry acknowledges that your application has been deployed, you should be able to find the application at the URI given. In the preceding example, you could find it at http://acloudyspringtime.cfapps.io/.
By default, metadata about the running application as well as service connection information is exposed to the application as environment variables (for example:$VCAP_SERVICES). This architecture decision is due to Cloud Foundry’s polyglot (any language and platform can be supported as a buildpack) nature. Process-scoped environment variables are language agnostic.
Environment variables do not always make for the easiest API, so Spring Boot automatically extracts them and flattens the data into properties that can be accessed through Spring’s Environment abstraction, as shown in the following example:
@Component class MyBean implements EnvironmentAware { private String instanceId; @Override public void setEnvironment(Environment environment) { this.instanceId = environment.getProperty("vcap.application.instance_id"); } // ... }
All Cloud Foundry properties are prefixed with vcap. You can use vcap properties to access application information (such as the public URL of the application) and service information (such as database credentials). See ‘CloudFoundryVcapEnvironmentPostProcessor’ Javadoc for complete details.
|
| The Spring Cloud Connectors project is a better fit for tasks such as configuring a DataSource. Spring Boot includes auto-configuration support and a |
Heroku is another popular PaaS platform. To customize Heroku builds, you provide a Procfile, which provides the incantation required to deploy an application. Heroku assigns a port for the Java application to use and then ensures that routing to the external URI works.
You must configure your application to listen on the correct port. The following example shows the Procfile for our starter REST application:
web: java -Dserver.port=$PORT -jar target/demo-0.0.1-SNAPSHOT.jar
Spring Boot makes -D arguments available as properties accessible from a Spring Environment instance. The server.port configuration property is fed to the embedded Tomcat, Jetty, or Undertow instance which, then uses the port when it starts up. The $PORT environment variable is assigned to us by the Heroku PaaS.
This should be everything you need. The most common deployment workflow for Heroku deployments is to git push the code to production, as shown in the following example:
$ git push heroku master
Initializing repository, done.
Counting objects: 95, done. Delta compression using up to 8 threads. Compressing objects: 100% (78/78), done. Writing objects: 100% (95/95), 8.66 MiB | 606.00 KiB/s, done. Total 95 (delta 31), reused 0 (delta 0) -----> Java app detected -----> Installing OpenJDK 1.8... done -----> Installing Maven 3.3.1... done -----> Installing settings.xml... done -----> Executing: mvn -B -DskipTests=true clean install [INFO] Scanning for projects... Downloading: http://repo.spring.io/... Downloaded: http://repo.spring.io/... (818 B at 1.8 KB/sec) .... Downloaded: http://s3pository.heroku.com/jvm/... (152 KB at 595.3 KB/sec) [INFO] Installing /tmp/build_0c35a5d2-a067-4abc-a232-14b1fb7a8229/target/... [INFO] Installing /tmp/build_0c35a5d2-a067-4abc-a232-14b1fb7a8229/pom.xml ... [INFO] ------------------------------------------------------------------------ [INFO] BUILD SUCCESS [INFO] ------------------------------------------------------------------------ [INFO] Total time: 59.358s [INFO] Finished at: Fri Mar 07 07:28:25 UTC 2014 [INFO] Final Memory: 20M/493M [INFO] ------------------------------------------------------------------------ -----> Discovering process types Procfile declares types -> web -----> Compressing... done, 70.4MB -----> Launching... done, v6 http://agile-sierra-1405.herokuapp.com/ deployed to Heroku To git@heroku.com:agile-sierra-1405.git * [new branch] master -> master
Your application should now be up and running on Heroku.
OpenShift is the Red Hat public (and enterprise) extension of the Kubernetes container orchestration platform. Similarly to Kubernetes, OpenShift has many options for installing Spring Boot based applications.
OpenShift has many resources describing how to deploy Spring Boot applications, which include:
Amazon Web Services offers multiple ways to install Spring Boot-based applications, either as traditional web applications (war) or as executable jar files with an embedded web server. The options include:
- AWS Elastic Beanstalk
- AWS Code Deploy
- AWS OPS Works
- AWS Cloud Formation
- AWS Container Registry
Each has different features and pricing model. In this document, we describe only the simplest option: AWS Elastic Beanstalk.
As described in the official Elastic Beanstalk Java guide, there are two main options to deploy a Java application. You can either use the “Tomcat Platform” or the “Java SE platform”.
This option applies to Spring Boot projects that produce a war file. There is no any special configuration required. You need only follow the official guide.
This option applies to Spring Boot projects that produce a jar file and run an embedded web container. Elastic Beanstalk environments run an nginx instance on port 80 to proxy the actual application, running on port 5000. To configure it, add the following line to your application.properties file:
server.port=5000
|
| By default, Elastic Beanstalk uploads sources and compiles them in AWS. However, it is best to upload the binaries instead. To do so, add the following lines to your deploy: artifact: target/demo-0.0.1-SNAPSHOT.jar |
|
| By default an Elastic Beanstalk environment is load balanced. The load balancer has a significant cost. To avoid that cost, set the environment type to “Single instance”, as described in the Amazon documentation. You can also create single instance environments by using the CLI and the following command: eb create -s |
This is one of the easiest ways to get to AWS, but there are more things to cover, such as how to integrate Elastic Beanstalk into any CI / CD tool, use the Elastic Beanstalk Maven plugin instead of the CLI, and others. There is a exampledriven.wordpress.com/2017/01/09/spring-boot-aws-elastic-beanstalk-example/ [blog post] covering these topics more in detail.
Boxfuse works by turning your Spring Boot executable jar or war into a minimal VM image that can be deployed unchanged either on VirtualBox or on AWS. Boxfuse comes with deep integration for Spring Boot and uses the information from your Spring Boot configuration file to automatically configure ports and health check URLs. Boxfuse leverages this information both for the images it produces as well as for all the resources it provisions (instances, security groups, elastic load balancers, and so on).
Once you have created a Boxfuse account, connected it to your AWS account, installed the latest version of the Boxfuse Client, and ensured that the application has been built by Maven or Gradle (by using, for example, mvn clean package), you can deploy your Spring Boot application to AWS with a command similar to the following:
$ boxfuse run myapp-1.0.jar -env=prod
See the boxfuse run documentation for more options. If there is a boxfuse.com/docs/commandline/#configuration [boxfuse.conf] file present in the current directory, it is considered.
|
| By default, Boxfuse activates a Spring profile named |
At this point, boxfuse creates an image for your application, uploads it, and configures and starts the necessary resources on AWS resulting in output similar to the following example:
Fusing Image for myapp-1.0.jar ... Image fused in 00:06.838s (53937 K) -> axelfontaine/myapp:1.0 Creating axelfontaine/myapp ... Pushing axelfontaine/myapp:1.0 ... Verifying axelfontaine/myapp:1.0 ... Creating Elastic IP ... Mapping myapp-axelfontaine.boxfuse.io to 52.28.233.167 ... Waiting for AWS to create an AMI for axelfontaine/myapp:1.0 in eu-central-1 (this may take up to 50 seconds) ... AMI created in 00:23.557s -> ami-d23f38cf Creating security group boxfuse-sg_axelfontaine/myapp:1.0 ... Launching t2.micro instance of axelfontaine/myapp:1.0 (ami-d23f38cf) in eu-central-1 ... Instance launched in 00:30.306s -> i-92ef9f53 Waiting for AWS to boot Instance i-92ef9f53 and Payload to start at http://52.28.235.61/ ... Payload started in 00:29.266s -> http://52.28.235.61/ Remapping Elastic IP 52.28.233.167 to i-92ef9f53 ... Waiting 15s for AWS to complete Elastic IP Zero Downtime transition ... Deployment completed successfully. axelfontaine/myapp:1.0 is up and running at http://myapp-axelfontaine.boxfuse.io/
Your application should now be up and running on AWS.
See the blog post on deploying Spring Boot apps on EC2 as well as the documentation for the Boxfuse Spring Boot integration to get started with a Maven build to run the app.
Google Cloud has several options that can be used to launch Spring Boot applications. The easiest to get started with is probably App Engine, but you could also find ways to run Spring Boot in a container with Container Engine or on a virtual machine with Compute Engine.
To run in App Engine, you can create a project in the UI first, which sets up a unique identifier for you and also sets up HTTP routes. Add a Java app to the project and leave it empty and then use the Google Cloud SDK to push your Spring Boot app into that slot from the command line or CI build.
App Engine needs you to create an app.yaml file to describe the resources your app requires. Normally you put this file in src/main/appengine, and it should resemble the following file:
service: default
runtime: java env: flex runtime_config: jdk: openjdk8 handlers: - url: /.* script: this field is required, but ignored manual_scaling: instances: 1 health_check: enable_health_check: False env_variables: ENCRYPT_KEY: your_encryption_key_here
You can deploy the app (for example, with a Maven plugin) by adding the project ID to the build configuration, as shown in the following example:
<plugin>
<groupId>com.google.cloud.tools</groupId> <artifactId>appengine-maven-plugin</artifactId> <version>1.3.0</version> <configuration> <project>myproject</project> </configuration> </plugin>
Then deploy with mvn appengine:deploy (if you need to authenticate first, the build fails).
|
| Google App Engine Classic is tied to the Servlet 2.5 API, so you cannot deploy a Spring Application there without some modifications. See the Servlet 2.5 section of this guide. |
In additional to running Spring Boot applications by using java -jar, it is also possible to make fully executable applications for Unix systems. A fully executable jar can be executed like any other executable binary or it can be registered with init.d or systemd. This makes it very easy to install and manage Spring Boot applications in common production environments.
|
| Fully executable jars work by embedding an extra script at the front of the file. Currently, some tools do not accept this format, so you may not always be able to use this technique. For example, |
To create a ‘fully executable’ jar with Maven, use the following plugin configuration:
<plugin>
<groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> <configuration> <executable>true</executable> </configuration> </plugin>
The following example shows the equivalent Gradle configuration:
bootJar {
launchScript()
}
You can then run your application by typing ./my-application.jar (where my-application is the name of your artifact). The directory containing the jar is used as your application’s working directory.
The default script supports most Linux distributions and is tested on CentOS and Ubuntu. Other platforms, such as OS X and FreeBSD, require the use of a customembeddedLaunchScript.
Spring Boot application can be easily started as Unix/Linux services by using either init.d or systemd.
If you configured Spring Boot’s Maven or Gradle plugin to generate a fully executable jar, and you do not use a custom embeddedLaunchScript, your application can be used as an init.d service. To do so, symlink the jar to init.d to support the standard start, stop, restart and status commands.
The script supports the following features:
- Starts the services as the user that owns the jar file
- Tracks the application’s PID by using
/var/run/<appname>/<appname>.pid - Writes console logs to
/var/log/<appname>.log
Assuming that you have a Spring Boot application installed in /var/myapp, to install a Spring Boot application as an init.d service, create a symlink, as follows:
$ sudo ln -s /var/myapp/myapp.jar /etc/init.d/myapp
Once installed, you can start and stop the service in the usual way. For example, on a Debian based system, you could start it with the following command:
$ service myapp start
|
| If your application fails to start, check the log file written to |
You can also flag the application to start automatically by using your standard operating system tools. For example, on Debian, you could use the following command:
$ update-rc.d myapp defaults <priority>
|
| The following is a set of guidelines on how to secure a Spring Boot application that runs as an init.d service. It is not intended to be an exhaustive list of everything that should be done to harden an application and the environment in which it runs. |
When executed as root, as is the case when root is being used to start an init.d service, the default executable script runs the application as the user who owns the jar file. You should never run a Spring Boot application as root, so your application’s jar file should never be owned by root. Instead, create a specific user to run your application and use chown to make it the owner of the jar file, as shown in the following example:
$ chown bootapp:bootapp your-app.jar
In this case, the default executable script runs the application as the bootapp user.
|
| To reduce the chances of the application’s user account being compromised, you should consider preventing it from using a login shell. For example, you can set the account’s shell to |
You should also take steps to prevent the modification of your application’s jar file. Firstly, configure its permissions so that it cannot be written and can only be read or executed by its owner, as shown in the following example:
$ chmod 500 your-app.jar
Second, you should also take steps to limit the damage if your application or the account that’s running it is compromised. If an attacker does gain access, they could make the jar file writable and change its contents. One way to protect against this is to make it immutable by using chattr, as shown in the following example:
$ sudo chattr +i your-app.jar
This will prevent any user, including root, from modifying the jar.
If root is used to control the application’s service and you use a .conf file to customize its startup, the .conf file is read and evaluated by the root user. It should be secured accordingly. Use chmod so that the file can only be read by the owner and use chown to make root the owner, as shown in the following example:
$ chmod 400 your-app.conf $ sudo chown root:root your-app.conf
systemd is the successor of the System V init system and is now being used by many modern Linux distributions. Although you can continue to use init.d scripts with systemd, it is also possible to launch Spring Boot applications by using systemd ‘service’ scripts.
Assuming that you have a Spring Boot application installed in /var/myapp, to install a Spring Boot application as a systemd service, create a script named myapp.service and place it in /etc/systemd/system directory. The following script offers an example:
[Unit] Description=myapp After=syslog.target [Service] User=myapp ExecStart=/var/myapp/myapp.jar SuccessExitStatus=143 [Install] WantedBy=multi-user.target
|
Important |
|---|---|
| Remember to change the |
|
| The |
Note that, unlike when running as an init.d service, the user that runs the application, the PID file, and the console log file are managed by systemd itself and therefore must be configured by using appropriate fields in the ‘service’ script. Consult the service unit configuration man page for more details.
To flag the application to start automatically on system boot, use the following command:
$ systemctl enable myapp.service
Refer to man systemctl for more details.
The default embedded startup script written by the Maven or Gradle plugin can be customized in a number of ways. For most people, using the default script along with a few customizations is usually enough. If you find you cannot customize something that you need to, you can always use the embeddedLaunchScript option to write your own file entirely.
It often makes sense to customize elements of the start script as it is written into the jar file. For example, init.d scripts can provide a “description”. Since you know the description up front (and it need not change), you may as well provide it when the jar is generated.
To customize written elements, use the embeddedLaunchScriptProperties option of the Spring Boot Maven or Gradle plugins.
The following property substitutions are supported with the default script:
| Name | Description |
|---|---|
|
|
The script mode. Defaults to |
|
|
The |
|
|
The |
|
|
The |
|
|
The |
|
|
The |
|
|
The |
|
|
The |
|
|
The |
|
|
The default value for |
|
|
Reference to a file script that should be inlined in the default launch script. This can be used to set environmental variables such as |
|
|
The default value for |
|
|
The default value for |
|
|
The default value for |
|
|
The default value for the name of the PID file in |
|
|
Whether the |
|
|
The default value for |
For items of the script that need to be customized after the jar has been written, you can use environment variables or a config file.
The following environment properties are supported with the default script:
| Variable | Description |
|---|---|
|
|
The “mode” of operation. The default depends on the way the jar was built but is usually |
|
|
Whether the |
|
|
The root name of the pid folder ( |
|
|
The name of the folder in which to put log files ( |
|
|
The name of the folder from which to read .conf files (same folder as jar-file by default). |
|
|
The name of the log file in the |
|
|
The name of the app. If the jar is run from a symlink, the script guesses the app name if it is not a symlink or you want to explicitly set the app name, this can be useful. |
|
|
The arguments to pass to the program (the Spring Boot app). |
|
|
The location of the |
|
|
Options that are passed to the JVM when it is launched. |
|
|
The explicit location of the jar file, in case the script is being used to launch a jar that it is not actually embedded. |
|
|
If not empty, sets the |
|
|
The time in seconds to wait when stopping the application before forcing a shutdown ( |
|
| The |
With the exception of JARFILE and APP_NAME, the above settings can be configured by using a .conf file. The file is expected to be next to the jar file and have the same name but suffixed with .conf rather than .jar. For example, a jar named /var/myapp/myapp.jar uses the configuration file named /var/myapp/myapp.conf.
myapp.conf.
JAVA_OPTS=-Xmx1024M LOG_FOLDER=/custom/log/folder
|
| If you do not like having the config file next to the jar file, you can set a |
To learn about securing this file appropriately, see the guidelines for securing an init.d service.
A Spring Boot application can be started as a Windows service by using winsw.
A sample (maintained separately) describes step-by-step how you can create a Windows service for your Spring Boot application.
Check out the Cloud Foundry, Heroku, OpenShift, and Boxfuse web sites for more information about the kinds of features that a PaaS can offer. These are just four of the most popular Java PaaS providers. Since Spring Boot is so amenable to cloud-based deployment, you can freely consider other providers as well.
The next section goes on to cover the Spring Boot CLI, or you can jump ahead to read about build tool plugins.
The Spring Boot CLI is a command line tool that you can use if you want to quickly develop a Spring application. It lets you run Groovy scripts, which means that you have a familiar Java-like syntax without so much boilerplate code. You can also bootstrap a new project or write your own command for it.
The Spring Boot CLI (Command-Line Interface) can be installed manually by using SDKMAN! (the SDK Manager) or by using Homebrew or MacPorts if you are an OSX user. See Section 10.2, “Installing the Spring Boot CLI” in the “Getting started” section for comprehensive installation instructions.
Once you have installed the CLI, you can run it by typing spring and pressing Enter at the command line. If you run spring without any arguments, a simple help screen is displayed, as follows:
$ spring
usage: spring [--help] [--version]
<command> [<args>]
Available commands are:
run [options] <files> [--] [args]
Run a spring groovy script
... more command help is shown here
You can type spring help to get more details about any of the supported commands, as shown in the following example:
$ spring help run
spring run - Run a spring groovy script
usage: spring run [options] <files> [--] [args]
Option Description
------ -----------
--autoconfigure [Boolean] Add autoconfigure compiler
transformations (default: true)
--classpath, -cp Additional classpath entries
-e, --edit Open the file with the default system
editor
--no-guess-dependencies Do not attempt to guess dependencies
--no-guess-imports Do not attempt to guess imports
-q, --quiet Quiet logging
-v, --verbose Verbose logging of dependency
resolution
--watch Watch the specified file for changes
The version command provides a quick way to check which version of Spring Boot you are using, as follows:
$ spring version Spring CLI v2.0.0.BUILD-SNAPSHOT
You can compile and run Groovy source code by using the run command. The Spring Boot CLI is completely self-contained, so you don’t need any external Groovy installation.
The following example shows a “hello world” web application written in Groovy:
hello.groovy.
@RestController class WebApplication { @RequestMapping("/") String home() { "Hello World!" } }
To compile and run the application type the following command:
$ spring run hello.groovy
To pass command-line arguments to the application, use a -- to separate the commands from the “spring” command arguments, as shown in the following example:
$ spring run hello.groovy -- --server.port=9000
To set JVM command line arguments, you can use the JAVA_OPTS environment variable, as shown in the following example:
$ JAVA_OPTS=-Xmx1024m spring run hello.groovy
|
| When setting |
Standard Groovy includes a @Grab annotation, which lets you declare dependencies on third-party libraries. This useful technique lets Groovy download jars in the same way as Maven or Gradle would but without requiring you to use a build tool.
Spring Boot extends this technique further and tries to deduce which libraries to “grab” based on your code. For example, since the WebApplication code shown previously uses @RestController annotations, Spring Boot grabs"`Tomcat`" and “Spring MVC”.
The following items are used as “grab hints”:
| Items | Grabs |
|---|---|
|
|
JDBC Application. |
|
|
JMS Application. |
|
|
Caching abstraction. |
|
|
JUnit. |
|
|
RabbitMQ. |
|
|
Project Reactor. |
| extends |
Spock test. |
|
|
Spring Batch. |
|
|
Spring Integration. |
|
|
Spring MVC + Embedded Tomcat. |
|
|
Spring Security. |
|
|
Spring Transaction Management. |
|
| See subclasses of |
Spring Boot extends Groovy’s standard @Grab support by letting you specify a dependency without a group or version (for example, @Grab('freemarker')). Doing so consults Spring Boot’s default dependency metadata to deduce the artifact’s group and version. Note that the default metadata is tied to the version of the CLI that you use – it changes only when you move to a new version of the CLI, putting you in control of when the versions of your dependencies may change. A table showing the dependencies and their versions that are included in the default metadata can be found in the appendix.
To help reduce the size of your Groovy code, several import statements are automatically included. Notice how the preceding example refers to @Component, @RestController, and @RequestMapping without needing to use fully-qualified names or import statements.
|
| Many Spring annotations work without using |
Unlike the equivalent Java application, you do not need to include a public static void main(String[] args) method with your Groovy scripts. ASpringApplication is automatically created, with your compiled code acting as the source.
By default, the CLI uses the dependency management declared in spring-boot-dependencies when resolving @Grab dependencies. Additional dependency management, which overrides the default dependency management, can be configured by using the @DependencyManagementBom annotation. The annotation’s value should specify the coordinates (groupId:artifactId:version) of one or more Maven BOMs.
For example, consider the following declaration:
@DependencyManagementBom("com.example.custom-bom:1.0.0")
The preceding declaration picks up custom-bom-1.0.0.pom in a Maven repository under com/example/custom-versions/1.0.0/.
When you specify multiple BOMs, they are applied in the order in which you declare them, as shown in the following example:
@DependencyManagementBom(["com.example.custom-bom:1.0.0",
"com.example.another-bom:1.0.0"])
The preceding example indicates that dependency management in another-bom overrides the dependency management in custom-bom.
You can use @DependencyManagementBom anywhere that you can use @Grab. However, to ensure consistent ordering of the dependency management, you can use@DependencyManagementBom at most once in your application. A useful source of dependency management (which is a superset of Spring Boot’s dependency management) is the Spring IO Platform, which you might include with the following line:
`@DependencyManagementBom('io.spring.platform:platform-bom:1.1.2.RELEASE')`.
You can use “shell globbing” with all commands that accept file input. Doing so lets you use multiple files from a single directory, as shown in the following example:
$ spring run *.groovy
You can use the jar command to package your application into a self-contained executable jar file, as shown in the following example:
$ spring jar my-app.jar *.groovy
The resulting jar contains the classes produced by compiling the application and all of the application’s dependencies so that it can then be run by using java -jar. The jar file also contains entries from the application’s classpath. You can add explicit paths to the jar by using --include and --exclude. Both are comma-separated, and both accept prefixes, in the form of “+” and “-”, to signify that they should be removed from the defaults. The default includes are as follows:
public/**, resources/**, static/**, templates/**, META-INF/**, *
The default excludes are as follows:
.*, repository/**, build/**, target/**, **/*.jar, **/*.groovy
Type spring help jar on the command line for more information.
The init command lets you create a new project by using start.spring.io without leaving the shell, as shown in the following example:
$ spring init --dependencies=web,data-jpa my-project Using service at https://start.spring.io Project extracted to '/Users/developer/example/my-project'
The preceding example creates a my-project directory with a Maven-based project that uses spring-boot-starter-web and spring-boot-starter-data-jpa. You can list the capabilities of the service by using the --list flag, as shown in the following example:
$ spring init --list ======================================= Capabilities of https://start.spring.io ======================================= Available dependencies: ----------------------- actuator - Actuator: Production ready features to help you monitor and manage your application ... web - Web: Support for full-stack web development, including Tomcat and spring-webmvc websocket - Websocket: Support for WebSocket development ws - WS: Support for Spring Web Services Available project types: ------------------------ gradle-build - Gradle Config [format:build, build:gradle] gradle-project - Gradle Project [format:project, build:gradle] maven-build - Maven POM [format:build, build:maven] maven-project - Maven Project [format:project, build:maven] (default) ...
The init command supports many options. See the help output for more details. For instance, the following command creates a Gradle project that uses Java 8 and war packaging:
$ spring init --build=gradle --java-version=1.8 --dependencies=websocket --packaging=war sample-app.zip Using service at https://start.spring.io Content saved to 'sample-app.zip'
Spring Boot includes command-line completion scripts for the BASH and zsh shells. If you do not use either of these shells (perhaps you are a Windows user), you can use the shell command to launch an integrated shell, as shown in the following example:
$ spring shell
Spring Boot (v2.0.0.BUILD-SNAPSHOT)
Hit TAB to complete. Type \'help' and hit RETURN for help, and \'exit' to quit.
From inside the embedded shell, you can run other commands directly:
$ version Spring CLI v2.0.0.BUILD-SNAPSHOT
The embedded shell supports ANSI color output as well as tab completion. If you need to run a native command, you can use the ! prefix. To exit the embedded shell, press ctrl-c.
You can add extensions to the CLI by using the install command. The command takes one or more sets of artifact coordinates in the format group:artifact:version, as shown in the following example:
$ spring install com.example:spring-boot-cli-extension:1.0.0.RELEASE
In addition to installing the artifacts identified by the coordinates you supply, all of the artifacts' dependencies are also installed.
To uninstall a dependency, use the uninstall command. As with the install command, it takes one or more sets of artifact coordinates in the format group:artifact:version, as shown in the following example:
$ spring uninstall com.example:spring-boot-cli-extension:1.0.0.RELEASE
It uninstalls the artifacts identified by the coordinates you supply and their dependencies.
To uninstall all additional dependencies, you can use the --all option, as shown in the following example:
$ spring uninstall --all
Spring Framework 4.0 has native support for a beans{} “DSL” (borrowed from Grails), and you can embed bean definitions in your Groovy application scripts by using the same format. This is sometimes a good way to include external features like middleware declarations, as shown in the following example:
@Configuration class Application implements CommandLineRunner { @Autowired SharedService service @Override void run(String... args) { println service.message } } import my.company.SharedService beans { service(SharedService) { message = "Hello World" } }
You can mix class declarations with beans{} in the same file as long as they stay at the top level, or, if you prefer, you can put the beans DSL in a separate file.
The Spring Boot CLI uses Aether, Maven’s dependency resolution engine, to resolve dependencies. The CLI makes use of the Maven configuration found in ~/.m2/settings.xml to configure Aether. The following configuration settings are honored by the CLI:
- Offline
- Mirrors
- Servers
- Proxies
-
Profiles
- Activation
- Repositories
- Active profiles
See Maven’s settings documentation for further information.
There are some sample groovy scripts available from the GitHub repository that you can use to try out the Spring Boot CLI. There is also extensive Javadoc throughout the source code.
If you find that you reach the limit of the CLI tool, you probably want to look at converting your application to a full Gradle or Maven built “Groovy project”. The next section covers Spring Boot’s "Build tool plugins", which you can use with Gradle or Maven.
Spring Boot provides build tool plugins for Maven and Gradle. The plugins offer a variety of features, including the packaging of executable jars. This section provides more details on both plugins as well as some help should you need to extend an unsupported build system. If you are just getting started, you might want to read “Chapter 13, Build Systems” from the “Part III, “Using Spring Boot”” section first.
The Spring Boot Maven Plugin provides Spring Boot support in Maven, letting you package executable jar or war archives and run an application “in-place”. To use it, you must use Maven 3.2 (or later).
|
| See the Spring Boot Maven Plugin Site for complete plugin documentation. |
To use the Spring Boot Maven Plugin, include the appropriate XML in the plugins section of your pom.xml, as shown in the following example:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <!-- ... --> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> <version>2.0.0.BUILD-SNAPSHOT</version> <executions> <execution> <goals> <goal>repackage</goal> </goals> </execution> </executions> </plugin> </plugins> </build> </project>
The preceding configuration repackages a jar or war that is built during the package phase of the Maven lifecycle. The following example shows both the repackaged jar as well as the original jar in the target directory:
$ mvn package $ ls target/*.jar target/myproject-1.0.0.jar target/myproject-1.0.0.jar.original
If you do not include the <execution/> configuration as shown in the prior example, you can run the plugin on its own (but only if the package goal is used as well). For example:
$ mvn package spring-boot:repackage $ ls target/*.jar target/myproject-1.0.0.jar target/myproject-1.0.0.jar.original
If you use a milestone or snapshot release, you also need to add the appropriate pluginRepository elements as shown in the following listing:
<pluginRepositories>
<pluginRepository> <id>spring-snapshots</id> <url>http://repo.spring.io/snapshot</url> </pluginRepository> <pluginRepository> <id>spring-milestones</id> <url>http://repo.spring.io/milestone</url> </pluginRepository> </pluginRepositories>
Once spring-boot-maven-plugin has been included in your pom.xml, it automatically tries to rewrite archives to make them executable by using the spring-boot:repackage goal. You should configure your project to build a jar or war (as appropriate) by using the usual packaging element, as shown in the following example:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <!-- ... --> <packaging>jar</packaging> <!-- ... --> </project>
Your existing archive is enhanced by Spring Boot during the package phase. The main class that you want to launch can either be specified by using a configuration option or by adding a Main-Class attribute to the manifest in the usual way. If you do not specify a main class, the plugin searches for a class with apublic static void main(String[] args) method.
To build and run a project artifact, you can type the following:
$ mvn package $ java -jar target/mymodule-0.0.1-SNAPSHOT.jar
To build a war file that is both executable and deployable into an external container, you need to mark the embedded container dependencies as “provided”, as shown in the following example:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <!-- ... --> <packaging>war</packaging> <!-- ... --> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-tomcat</artifactId> <scope>provided</scope> </dependency> <!-- ... --> </dependencies> </project>
|
| See the “Section 86.1, “Create a Deployable War File”” section for more details on how to create a deployable war file. |
Advanced configuration options and examples are available in the plugin info page.
The Spring Boot Gradle Plugin provides Spring Boot support in Gradle, letting you package executable jar or war archives, run Spring Boot applications, and use the dependency management provided by spring-boot-dependencies. It requires Gradle 4.0 or later. Please refer to the plugin’s documentation to learn more:
The Spring Boot AntLib module provides basic Spring Boot support for Apache Ant. You can use the module to create executable jars. To use the module, you need to declare an additional spring-boot namespace in your build.xml, as shown in the following example:
<project xmlns:ivy="antlib:org.apache.ivy.ant" xmlns:spring-boot="antlib:org.springframework.boot.ant" name="myapp" default="build"> ... </project>
You need to remember to start Ant using the -lib option, as shown in the following example:
$ ant -lib <folder containing spring-boot-antlib-2.0.0.BUILD-SNAPSHOT.jar>
|
| The “Using Spring Boot” section includes a more complete example of using Apache Ant with |
Once the spring-boot-antlib namespace has been declared, the following additional tasks are available:
You can use the exejar task to create a Spring Boot executable jar. The following attributes are supported by the task:
| Attribute | Description | Required |
|---|---|---|
|
|
The destination jar file to create |
Yes |
|
|
The root directory of Java class files |
Yes |
|
|
The main application class to run |
No (default is first class found declaring a |
The following nested elements can be used with the task:
| Element | Description |
|---|---|
|
|
One or more Resource Collections describing a set of Resources that should be added to the content of the created jar file. |
|
|
One or more Resource Collections that should be added to the set of jar libraries that make up the runtime dependency classpath of the application. |
Specify start-class.
<spring-boot:exejar destfile="target/my-application.jar" classes="target/classes" start-class="com.foo.MyApplication"> <resources> <fileset dir="src/main/resources" /> </resources> <lib> <fileset dir="lib" /> </lib> </spring-boot:exejar>
Detect start-class.
<exejar destfile="target/my-application.jar" classes="target/classes"> <lib> <fileset dir="lib" /> </lib> </exejar>
The findmainclass task is used internally by exejar to locate a class declaring a main. You can also use this task directly in your build, if needed. The following attributes are supported:
| Attribute | Description | Required |
|---|---|---|
|
|
The root directory of Java class files |
Yes (unless |
|
|
Can be used to short-circuit the |
No |
|
|
The Ant property that should be set with the result |
No (result will be logged if unspecified) |
If you want to use a build tool other than Maven, Gradle, or Ant, you likely need to develop your own plugin. Executable jars need to follow a specific format and certain entries need to be written in an uncompressed form (see the “executable jar format” section in the appendix for details).
The Spring Boot Maven and Gradle plugins both make use of spring-boot-loader-tools to actually generate jars. If you need to, you may use this library directly.
To repackage an existing archive so that it becomes a self-contained executable archive, use org.springframework.boot.loader.tools.Repackager. The Repackager class takes a single constructor argument that refers to an existing jar or war archive. Use one of the two available repackage() methods to either replace the original file or write to a new destination. Various settings can also be configured on the repackager before it is run.
When repackaging an archive, you can include references to dependency files by using the org.springframework.boot.loader.tools.Libraries interface. We do not provide any concrete implementations of Libraries here as they are usually build-system-specific.
If your archive already includes libraries, you can use Libraries.NONE.
If you do not use Repackager.setMainClass() to specify a main class, the repackager uses ASM to read class files and tries to find a suitable class with a public static void main(String[] args) method. An exception is thrown if more than one candidate is found.
The following listing shows a typical example repackage:
Repackager repackager = new Repackager(sourceJarFile);
repackager.setBackupSource(false);
repackager.repackage(new Libraries() { @Override public void doWithLibraries(LibraryCallback callback) throws IOException { // Build system specific implementation, callback for each dependency // callback.library(new Library(nestedFile, LibraryScope.COMPILE)); } });
If you are interested in how the build tool plugins work, you can look at the spring-boot-tools module on GitHub. More technical details of the executable jar format are covered in the appendix.
If you have specific build-related questions, you can check out the “how-to” guides.
This section provides answers to some common ‘how do I do that…’ questions that often arise when using Spring Boot. Its coverage is not exhaustive, but it does cover quite a lot.
If you have a specific problem that we do not cover here, you might want to check out stackoverflow.com to see if someone has already provided an answer. This is also a great place to ask new questions (please use the spring-boot tag).
We are also more than happy to extend this section. If you want to add a ‘how-to’, send us a pull request.
FailureAnalyzer is a great way to intercept an exception on startup and turn it into a human-readable message, wrapped in a FailureAnalysis. Spring Boot provides such an analyzer for application-context-related exceptions, JSR-303 validations, and more. You can also create your own.
AbstractFailureAnalyzer is a convenient extension of FailureAnalyzer that checks the presence of a specified exception type in the exception to handle. You can extend from that so that your implementation gets a chance to handle the exception only when it is actually present. If, for whatever reason, you cannot handle the exception, return null to give another implementation a chance to handle the exception.
FailureAnalyzer implementations must be registered in META-INF/spring.factories. The following example registers ProjectConstraintViolationFailureAnalyzer:
org.springframework.boot.diagnostics.FailureAnalyzer=\
com.example.ProjectConstraintViolationFailureAnalyzer
The Spring Boot auto-configuration tries its best to ‘do the right thing’, but sometimes things fail, and it can be hard to tell why.
There is a really useful ConditionEvaluationReport available in any Spring Boot ApplicationContext. You can see it if you enable DEBUG logging output. If you use the spring-boot-actuator, there is also a conditions endpoint that renders the report in JSON. Use that endpoint to debug the application and see what features have been added (and which not) by Spring Boot at runtime.
Many more questions can be answered by looking at the source code and the Javadoc. When reading the code, remember the following rules of thumb:
- Look for classes called
*AutoConfigurationand read their sources. Pay special attention to the@Conditional*annotations to find out what features they enable and when. Add--debugto the command line or a System property-Ddebugto get a log on the console of all the auto-configuration decisions that were made in your app. In a running Actuator app, look at theconditionsendpoint (/application/conditionsor the JMX equivalent) for the same information. - Look for classes that are
@ConfigurationProperties(such asServerProperties) and read from there the available external configuration options. The@ConfigurationPropertieshas anameattribute that acts as a prefix to external properties. Thus,ServerPropertieshasprefix="server"and its configuration properties areserver.port,server.address, and others. In a running Actuator app, look at theconfigpropsendpoint. - Look for uses of the
bindmethod on theBinderto pull configuration values explicitly out of theEnvironmentin a relaxed manner. It is often used with a prefix. - Look for
@Valueannotations that bind directly to theEnvironment. - Look for
@ConditionalOnExpressionannotations that switch features on and off in response to SpEL expressions, normally evaluated with placeholders resolved from theEnvironment.
A SpringApplication has ApplicationListeners and ApplicationContextInitializers that are used to apply customizations to the context or environment. Spring Boot loads a number of such customizations for use internally from META-INF/spring.factories. There is more than one way to register additional ones:
- Programmatically, per application, by calling the
addListenersandaddInitializersmethods onSpringApplicationbefore you run it. - Declaratively, per application, by setting the
context.initializer.classesorcontext.listener.classesproperties. - Declaratively, for all applications, by adding a
META-INF/spring.factoriesand packaging a jar file that the applications all use as a library.
The SpringApplication sends some special ApplicationEvents to the listeners (some even before the context is created) and then registers the listeners for events published by the ApplicationContext as well. See “Section 23.4, “Application Events and Listeners”” in the ‘Spring Boot features’ section for a complete list.
It is also possible to customize the Environment before the application context is refreshed by using EnvironmentPostProcessor. Each implementation should be registered in META-INF/spring.factories, as shown in the following example:
org.springframework.boot.env.EnvironmentPostProcessor=com.example.YourEnvironmentPostProcessor
The implementation can load arbitrary files and add them to the Environment. For instance, the following example loads a YAML configuration file from the classpath:
public class EnvironmentPostProcessorExample implements EnvironmentPostProcessor { private final YamlPropertySourceLoader loader = new YamlPropertySourceLoader(); @Override public void postProcessEnvironment(ConfigurableEnvironment environment, SpringApplication application) { Resource path = new ClassPathResource("com/example/myapp/config.yml"); PropertySource<?> propertySource = loadYaml(path); environment.getPropertySources().addLast(propertySource); } private PropertySource<?> loadYaml(Resource path) { if (!path.exists()) { throw new IllegalArgumentException("Resource " + path + " does not exist"); } try { return this.loader.load("custom-resource", path, null); } catch (IOException ex) { throw new IllegalStateException( "Failed to load yaml configuration from " + path, ex); } } }
|
| The |
|
Caution |
|---|---|
| While using |
You can use the ApplicationBuilder class to create parent/child ApplicationContext hierarchies. See “Section 23.3, “Fluent Builder API”” in the ‘Spring Boot features’ section for more information.
Not all Spring applications have to be web applications (or web services). If you want to execute some code in a main method but also bootstrap a Spring application to set up the infrastructure to use, you can use the SpringApplication features of Spring Boot. A SpringApplication changes its ApplicationContext class, depending on whether it thinks it needs a web application or not. The first thing you can do to help it is to leave the servlet API dependencies off the classpath. If you cannot do that (for example, you run two applications from the same code base) then you can explicitly call setWebEnvironment(false) on your SpringApplicationinstance or set the applicationContextClass property (through the Java API or with external properties). Application code that you want to run as your business logic can be implemented as a CommandLineRunner and dropped into the context as a @Bean definition.
Rather than hardcoding some properties that are also specified in your project’s build configuration, you can automatically expand them by instead using the existing build configuration. This is possible in both Maven and Gradle.
You can automatically expand properties from the Maven project by using resource filtering. If you use the spring-boot-starter-parent, you can then refer to your Maven ‘project properties’ with @..@ placeholders, as shown in the following example:
app.encoding=@project.build.sourceEncoding@
app.java.version=@java.version@
|
| Only production configuration is filtered that way (in other words, no filtering is applied on |
|
| If you enable the |
If you do not use the starter parent, you need to include the following element inside the <build/> element of your pom.xml:
<resources>
<resource> <directory>src/main/resources</directory> <filtering>true</filtering> </resource> </resources>
You also need to include the following element inside <plugins/>:
<plugin>
<groupId>org.apache.maven.plugins</groupId> <artifactId>maven-resources-plugin</artifactId> <version>2.7</version> <configuration> <delimiters> <delimiter>@</delimiter> </delimiters> <useDefaultDelimiters>false</useDefaultDelimiters> </configuration> </plugin>
|
| The |
You can automatically expand properties from the Gradle project by configuring the Java plugin’s processResources task to do so, as shown in the following example:
processResources {
expand(project.properties)
}
You can then refer to your Gradle project’s properties via placeholders, as shown in the following example:
app.name=${name}
app.description=${description}
|
| Gradle’s |
A SpringApplication has bean properties (mainly setters), so you can use its Java API as you create the application to modify its behavior. Alternatively, you can externalize the configuration using properties in spring.main.*. For example, in application.properties, you might have the following settings:
spring.main.web-environment=false
spring.main.banner-mode=off
Then the Spring Boot banner is not printed on startup, and the application is not a web application.
|
| The preceding example also demonstrates how flexible binding allows the use of underscores ( |
Properties defined in external configuration overrides the values specified with the Java API, with the notable exception of the sources used to create the ApplicationContext. Consider the following application:
new SpringApplicationBuilder()
.bannerMode(Banner.Mode.OFF)
.sources(demo.MyApp.class) .run(args);
Now consider the following configuration:
spring.main.sources=com.acme.Config,com.acme.ExtraConfig
spring.main.banner-mode=console
The actual application now shows the banner (as overridden by configuration) and uses three sources for the ApplicationContext (in the following order): demo.MyApp, com.acme.Config, com.acme.ExtraConfig.
By default, properties from different sources are added to the Spring Environment in a defined order (see “Chapter 24, Externalized Configuration” in the ‘Spring Boot features’ section for the exact order).
A nice way to augment and modify this ordering is to add @PropertySource annotations to your application sources. Classes passed to the SpringApplication static convenience methods and those added using setSources() are inspected to see if they have @PropertySources. If they do, those properties are added to the Environment early enough to be used in all phases of the ApplicationContext lifecycle. Properties added in this way have lower priority than any added by using the default locations (such as application.properties), system properties, environment variables, or the command line.
You can also provide the following System properties (or environment variables) to change the behavior:
spring.config.name(SPRING_CONFIG_NAME): Defaults toapplicationas the root of the file name.spring.config.location(SPRING_CONFIG_LOCATION): The file to load (such as a classpath resource or a URL). A separateEnvironmentproperty source is set up for this document and it can be overridden by system properties, environment variables, or the command line.
No matter what you set in the environment, Spring Boot always loads application.properties as described above. By default, if YAML is used, then files with the ‘.yml’ extension are also added to the list.
Spring Boot logs the configuration files that are loaded at the DEBUG level and the candidates it has not found at TRACE level.
See ConfigFileApplicationListener for more detail.
Some people like to use (for example) --port=9000 instead of --server.port=9000 to set configuration properties on the command line. You can enable this behavior by using placeholders in application.properties, as shown in the following example:
server.port=${port:8080}
|
| If you inherit from the |
|
| In this specific case, the port binding works in a PaaS environment such as Heroku or Cloud Foundry In those two platforms, the |
YAML is a superset of JSON and, as such, is a convenient syntax for storing external properties in a hierarchical format, as shown in the following example:
spring:
application: name: cruncher datasource: driverClassName: com.mysql.jdbc.Driver url: jdbc:mysql://localhost/test server: port: 9000
Create a file called application.yml and put it in the root of your classpath. Then add snakeyaml to your dependencies (Maven coordinates org.yaml:snakeyaml, already included if you use the spring-boot-starter). A YAML file is parsed to a Java Map<String,Object> (like a JSON object), and Spring Boot flattens the map so that it is one level deep and has period-separated keys, as many people are used to with Properties files in Java.
The example YAML above corresponds to an application.properties file as follows:
spring.application.name=cruncher
spring.datasource.driverClassName=com.mysql.jdbc.Driver spring.datasource.url=jdbc:mysql://localhost/test server.port=9000
See “Section 24.6, “Using YAML Instead of Properties”” in the ‘Spring Boot features’ section for more information about YAML.
The Spring Environment has an API for this, but you would normally set a System property (spring.profiles.active) or an OS environment variable (SPRING_PROFILES_ACTIVE). Also, you can launch your application with a -D argument (remember to put it before the main class or jar archive), as follows:
$ java -jar -Dspring.profiles.active=production demo-0.0.1-SNAPSHOT.jar
In Spring Boot, you can also set the active profile in application.properties, as shown in the following example:
spring.profiles.active=production
A value set this way is replaced by the System property or environment variable setting but not by the SpringApplicationBuilder.profiles() method. Thus, the latter Java API can be used to augment the profiles without changing the defaults.
See “Chapter 25, Profiles” in the “Spring Boot features” section for more information.
A YAML file is actually a sequence of documents separated by --- lines, and each document is parsed separately to a flattened map.
If a YAML document contains a spring.profiles key, then the profiles value (a comma-separated list of profiles) is fed into the SpringEnvironment.acceptsProfiles() method. If any of those profiles is active, that document is included in the final merge (otherwise not), as shown in the following example:
server:
port: 9000 --- spring: profiles: development server: port: 9001 --- spring: profiles: production server: port: 0
In the preceding example, the default port is 9000. However, if the Spring profile called ‘development’ is active, then the port is 9001. If ‘production’ is active, then the port is 0.
The YAML documents are merged in the order in which they are encountered (so later values override earlier ones).
To do the same thing with properties files, you can use application-${profile}.properties to specify profile-specific values.
Spring Boot binds external properties from application.properties (or .yml) (and other places) into an application at runtime. There is not (and technically cannot be) an exhaustive list of all supported properties in a single location, because contributions can come from additional jar files on your classpath.
A running application with the Actuator features has a configprops endpoint that shows all the bound and bindable properties available through @ConfigurationProperties.
The appendix includes an application.properties example with a list of the most common properties supported by Spring Boot. The definitive list comes from searching the source code for @ConfigurationProperties and @Value annotations as well as the occasional use of Binder.
Each Spring Boot web application includes an embedded web server. This feature leads to a number of how-to questions, including how to change the embedded server and how to configure the embedded server. This section answers those questions.
Many Spring Boot starters include default embedded containers. spring-boot-starter-web includes Tomcat by including spring-boot-starter-tomcat, but you can use spring-boot-starter-jetty and spring-boot-starter-undertow instead. spring-boot-starter-webflux includes Reactor Netty by includingspring-boot-starter-reactor-netty, but you can use spring-boot-starter-tomcat, spring-boot-starter-jetty, and spring-boot-starter-undertowinstead.
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If you need to use a different HTTP server, you need to exclude the default dependencies and include the one you need. Spring Boot provides separate starters for HTTP servers to help make this process as easy as possible.
The following Maven example shows how to exclude Tomcat and include Jetty for Spring MVC:
<dependency>
<groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> <exclusions> <!-- Exclude the Tomcat dependency --> <exclusion> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-tomcat</artifactId> </exclusion> </exclusions> </dependency> <!-- Use Jetty instead --> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-jetty</artifactId> </dependency>
The following Gradle example shows how to exclude Netty and include Undertow for Spring WebFlux:
configurations {
// exclude Reactor Netty
compile.exclude module: 'spring-boot-starter-reactor-netty' } dependencies { compile 'org.springframework.boot:spring-boot-starter-webflux' // Use Undertow instead compile 'org.springframework.boot:spring-boot-starter-undertow' // ... }
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Generally, you can follow the advice from “Section 73.8, “Discover Built-in Options for External Properties”” about @ConfigurationProperties (ServerProperties is the main one here). However, you should also look at ServletWebServerFactoryCustomizer. The Jetty APIs are quite rich, so, once you have access to the JettyServletWebServerFactory, you can modify it in a number of ways. Alternatively, if you need more control and customization, you can add your ownJettyServletWebServerFactory.
There are two ways to add Servlet, Filter, ServletContextListener, and the other listeners supported by the Servlet spec to your application. You can either provide Spring beans for them or enable scanning for Servlet components.
To add a Servlet, Filter, or Servlet *Listener by using a Spring bean, you must provide a @Bean definition for it. Doing so can be very useful when you want to inject configuration or dependencies. However, you must be very careful that they do not cause eager initialization of too many other beans, because they have to be installed in the container very early in the application lifecycle (for example, it is not a good idea to have them depend on your DataSource or JPA configuration). You can work around restrictions like that by initializing the beans lazily when first used instead of on initialization.
In the case of Filters and Servlets, you can also add mappings and init parameters by adding a FilterRegistrationBean or a ServletRegistrationBeaninstead of or in addition to the underlying component.
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As described above, any Servlet or Filter beans are registered with the servlet container automatically. To disable registration of a particular Filter or Servletbean, create a registration bean for it and mark it as disabled, as shown in the following example:
@Bean public FilterRegistrationBean registration(MyFilter filter) { FilterRegistrationBean registration = new FilterRegistrationBean(filter); registration.setEnabled(false); return registration; }
@WebServlet, @WebFilter, and @WebListener annotated classes can be automatically registered with an embedded servlet container by annotating a @Configuration class with @ServletComponentScan and specifying the package(s) containing the components that you want to register. By default, @ServletComponentScan scans from the package of the annotated class.
In a standalone application, the main HTTP port defaults to 8080 but can be set with server.port (for example, in application.properties or as a System property). Thanks to relaxed binding of Environment values, you can also use SERVER_PORT (for example, as an OS environment variable).
To switch off the HTTP endpoints completely but still create a WebApplicationContext, use server.port=-1. (Doing so is sometimes useful for testing.)
For more details, see “Section 27.4.4, “Customizing Embedded Servlet Containers”” in the ‘Spring Boot features’ section, or the ServerProperties source code.
To scan for a free port (using OS natives to prevent clashes) use server.port=0.
You can access the port the server is running on from log output or from the ServletWebServerApplicationContext through its EmbeddedWebServer. The best way to get that and be sure that it has been initialized is to add a @Bean of type ApplicationListener<ServletWebServerInitializedEvent> and pull the container out of the event when it is published.
Tests that use @SpringBootTest(webEnvironment=WebEnvironment.RANDOM_PORT) can also inject the actual port into a field by using the @LocalServerPortannotation, as shown in the following example:
@RunWith(SpringJUnit4ClassRunner.class) @SpringBootTest(webEnvironment=WebEnvironment.RANDOM_PORT) public class MyWebIntegrationTests { @Autowired ServletWebServerApplicationContext server; @LocalServerPort int port; // ... }
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SSL can be configured declaratively by setting the various server.ssl.* properties, typically in application.properties or application.yml. The following example shows setting SSL properties in application.properties:
server.port=8443
server.ssl.key-store=classpath:keystore.jks server.ssl.key-store-password=secret server.ssl.key-password=another-secret
See Ssl for details of all of the supported properties.
Using configuration such as the preceding example means the application no longer supports a plain HTTP connector at port 8080. Spring Boot does not support the configuration of both an HTTP connector and an HTTPS connector through application.properties. If you want to have both, you need to configure one of them programmatically. We recommend using application.properties to configure HTTPS, as the HTTP connector is the easier of the two to configure programmatically. See the spring-boot-sample-tomcat-multi-connectors sample project for an example.
You can enable HTTP/2 support in your Spring Boot application with the server.http2.enabled configuration property. This support depends on the chosen web server and the application environment, since that protocol is not supported out-of-the-box by JDK8.
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Currently, only Undertow and Tomcat are supported with this configuration key.
As of Undertow 1.4.0+, HTTP/2 is supported without any additional requirement on JDK8.
Spring Boot ships by default with Tomcat 8.5.x; with that version, HTTP/2 is only supported if the libtcnative library and its dependencies are installed on the host operating system.
The library folder must be made available, if not already, to the JVM library path; this can be done with a JVM argument such as-Djava.library.path=/usr/local/opt/tomcat-native/lib. More on this in the official Tomcat documentation.
Starting Tomcat 8.5.x without that native support will log the following error:
ERROR 8787 --- [ main] o.a.coyote.http11.Http11NioProtocol : The upgrade handler [org.apache.coyote.http2.Http2Protocol] for [h2] only supports upgrade via ALPN but has been configured for the ["https-jsse-nio-8443"] connector that does not support ALPN.
This error is not fatal, and the application starts with HTTP/1.1 SSL support still.
Running your application with Tomcat 9.0.x and JDK9 doesn’t require any native library installed. To use Tomcat 9, you can override the tomcat.version build property with the version of your choice.
Access logs can be configured for Tomcat, Undertow, and Jetty through their respective namespaces.
For instance, the following settings log access on Tomcat with a custom pattern.
server.tomcat.basedir=my-tomcat
server.tomcat.accesslog.enabled=true server.tomcat.accesslog.pattern=%t %a "%r" %s (%D ms)
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Access logging for undertow can be configured in a similar fashion, as shown in the following example:
server.undertow.accesslog.enabled=true
server.undertow.accesslog.pattern=%t %a "%r" %s (%D ms)
Logs are stored in a logs directory relative to the working directory of the application. You can customize this location by setting theserver.undertow.accesslog.directory property.
Finally, access logging for Jetty can also be configured as follows:
server.jetty.accesslog.enabled=true
server.jetty.accesslog.filename=/var/log/jetty-access.log
By default, logs are redirected to System.err. For more details, see the documentation.
Your application might need to send 302 redirects or render content with absolute links back to itself. When running behind a proxy, the caller wants a link to the proxy and not to the physical address of the machine hosting your app. Typically, such situations are handled through a contract with the proxy, which adds headers to tell the back end how to construct links to itself.
If the proxy adds conventional X-Forwarded-For and X-Forwarded-Proto headers (most proxy server do so), the absolute links should be rendered correctly, provided server.use-forward-headers is set to true in your application.properties.
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If you use Tomcat, you can additionally configure the names of the headers used to carry “forwarded” information, as shown in the following example:
server.tomcat.remote-ip-header=x-your-remote-ip-header server.tomcat.protocol-header=x-your-protocol-header
Tomcat is also configured with a default regular expression that matches internal proxies that are to be trusted. By default, IP addresses in 10/8, 192.168/16,169.254/16 and 127/8 are trusted. You can customize the valve’s configuration by adding an entry to application.properties, as shown in the following example:
server.tomcat.internal-proxies=192\\.168\\.\\d{1,3}\\.\\d{1,3}
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You can take complete control of the configuration of Tomcat’s RemoteIpValve by switching the automatic one off (to do so, set server.use-forward-headers=false) and adding a new valve instance in a TomcatServletWebServerFactory bean.
Generally, you can follow the advice from “Section 73.8, “Discover Built-in Options for External Properties”” about @ConfigurationProperties (ServerProperties is the main one here). However, you should also look at ServletWebServerFactoryCustomizer and various Tomcat-specific *Customizers that you can add. The Tomcat APIs are quite rich, so, once you have access to the TomcatServletWebServerFactory, you can modify it in a number of ways. Alternatively, if you need more control and customization, you can add your own TomcatServletWebServerFactory.
You can add an org.apache.catalina.connector.Connector to the TomcatServletWebServerFactory, which can allow multiple connectors, including HTTP and HTTPS connectors, as shown in the following example:
@Bean public ServletWebServerFactory servletContainer() { TomcatServletWebServerFactory tomcat = new TomcatServletWebServerFactory(); tomcat.addAdditionalTomcatConnectors(createSslConnector()); return tomcat; } private Connector createSslConnector() { Connector connector = new Connector("org.apache.coyote.http11.Http11NioProtocol"); Http11NioProtocol protocol = (Http11NioProtocol) connector.getProtocolHandler(); try { File keystore = new ClassPathResource("keystore").getFile(); File truststore = new ClassPathResource("keystore").getFile(); connector.setScheme("https"); connector.setSecure(true); connector.setPort(8443); protocol.setSSLEnabled(true); protocol.setKeystoreFile(keystore.getAbsolutePath()); protocol.setKeystorePass("changeit"); protocol.setTruststoreFile(truststore.getAbsolutePath()); protocol.setTruststorePass("changeit"); protocol.setKeyAlias("apitester"); return connector; } catch (IOException ex) { throw new IllegalStateException("can't access keystore: [" + "keystore" + "] or truststore: [" + "keystore" + "]", ex); } }
By default, the embedded Tomcat used by Spring Boot does not support "Version 0" of the Cookie format, so you may see the following error:
java.lang.IllegalArgumentException: An invalid character [32] was present in the Cookie value
If at all possible, you should consider updating your code to only store values compliant with later Cookie specifications. If, however, you cannot change the way that cookies are written, you can instead configure Tomcat to use a LegacyCookieProcessor. To switch to the LegacyCookieProcessor, use anServletWebServerFactoryCustomizer bean that adds a TomcatContextCustomizer, as shown in the following example:
@Bean public WebServerFactoryCustomizer<TomcatServletWebServerFactory> cookieProcessorCustomizer() { return (serverFactory) -> serverFactory.addContextCustomizers( (context) -> context.setCookieProcessor(new LegacyCookieProcessor())); }
Generally you can follow the advice from “Section 73.8, “Discover Built-in Options for External Properties”” about @ConfigurationProperties (ServerPropertiesand ServerProperties.Undertow are the main ones here). However, you should also look at ServletWebServerFactoryCustomizer. Once you have access to the UndertowServletWebServerFactory, you can use an UndertowBuilderCustomizer to modify Undertow’s configuration to meet your needs. Alternatively, if you need more control and customization, you can add your own UndertowServletWebServerFactory.
Add an UndertowBuilderCustomizer to the UndertowServletWebServerFactory and add a listener to the Builder, as shown in the following example:
@Bean public UndertowServletWebServerFactory servletWebServerFactory() { UndertowServletWebServerFactory factory = new UndertowServletWebServerFactory(); factory.addBuilderCustomizers(new UndertowBuilderCustomizer() { @Override public void customize(Builder builder) { builder.addHttpListener(8080, "0.0.0.0"); } }); return factory; }
If you want to use @ServerEndpoint in a Spring Boot application that used an embedded container, you must declare a single ServerEndpointExporter @Bean, as shown in the following example:
@Bean public ServerEndpointExporter serverEndpointExporter() { return new ServerEndpointExporter(); }
The bean shown in the preceding example registers any @ServerEndpoint annotated beans with the underlying WebSocket container. When deployed to a standalone servlet container, this role is performed by a servlet container initializer, and the ServerEndpointExporter bean is not required.
HTTP response compression is supported by Jetty, Tomcat, and Undertow. It can be enabled in application.properties, as follows:
server.compression.enabled=true
By default, responses must be at least 2048 bytes in length for compression to be performed. You can configure this behavior by setting theserver.compression.min-response-size property.
By default, responses are compressed only if their content type is one of the following:
text/htmltext/xmltext/plaintext/css
You can configure this behavior by setting the server.compression.mime-types property.
Spring Boot has a number of starters that include Spring MVC. Note that some starters include a dependency on Spring MVC rather than include it directly. This section answers common questions about Spring MVC and Spring Boot.
Any Spring @RestController in a Spring Boot application should render JSON response by default as long as Jackson2 is on the classpath, as shown in the following example:
@RestController public class MyController { @RequestMapping("/thing") public MyThing thing() { return new MyThing(); } }
As long as MyThing can be serialized by Jackson2 (true for a normal POJO or Groovy object), then localhost:8080/thing serves a JSON representation of it by default. Note that, in a browser, you might sometimes see XML responses, because browsers tend to send accept headers that prefer XML.
If you have the Jackson XML extension (jackson-dataformat-xml) on the classpath, you can use it to render XML responses. The previous example that we used for JSON would work. To use the Jackson XML renderer, add the following dependency to your project:
<dependency>
<groupId>com.fasterxml.jackson.dataformat</groupId> <artifactId>jackson-dataformat-xml</artifactId> </dependency>
You may also want to add a dependency on Woodstox. It is faster than the default StAX implementation provided by the JDK and also adds pretty-print support and improved namespace handling. The following listing shows how to include a dependency on Woodstox:
<dependency>
<groupId>org.codehaus.woodstox</groupId> <artifactId>woodstox-core-asl</artifactId> </dependency>
If Jackson’s XML extension is not available, JAXB (provided by default in the JDK) is used, with the additional requirement of having MyThing annotated as@XmlRootElement, as shown in the following example:
@XmlRootElement public class MyThing { private String name; // .. getters and setters }
To get the server to render XML instead of JSON, you might have to send an Accept: text/xml header (or use a browser).
Spring MVC (client and server side) uses HttpMessageConverters to negotiate content conversion in an HTTP exchange. If Jackson is on the classpath, you already get the default converter(s) provided by Jackson2ObjectMapperBuilder, an instance of which is auto-configured for you.
The ObjectMapper (or XmlMapper for Jackson XML converter) instance (created by default) has the following customized properties:
MapperFeature.DEFAULT_VIEW_INCLUSIONis disabledDeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIESis disabled
Spring Boot has also some features to make it easier to customize this behavior.
You can configure the ObjectMapper and XmlMapper instances by using the environment. Jackson provides an extensive suite of simple on/off features that can be used to configure various aspects of its processing. These features are described in six enums (in Jackson) that map onto properties in the environment:
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For example, to enable pretty print, set spring.jackson.serialization.indent_output=true. Note that, thanks to the use of relaxed binding, the case of indent_output does not have to match the case of the corresponding enum constant, which is INDENT_OUTPUT.
This environment-based configuration is applied to the auto-configured Jackson2ObjectMapperBuilder bean and applies to any mappers created by using the builder, including the auto-configured ObjectMapper bean.
The context’s Jackson2ObjectMapperBuilder can be customized by one or more Jackson2ObjectMapperBuilderCustomizer beans. Such customizer beans can be ordered (Boot’s own customizer has an order of 0), letting additional customization be applied both before and after Boot’s customization.
Any beans of type com.fasterxml.jackson.databind.Module are automatically registered with the auto-configured Jackson2ObjectMapperBuilder and are applied to any ObjectMapper instances that it creates. This provides a global mechanism for contributing custom modules when you add new features to your application.
If you want to replace the default ObjectMapper completely, either define a @Bean of that type and mark it as @Primary or, if you prefer the builder-based approach, define a Jackson2ObjectMapperBuilder @Bean. Note that, in either case, doing so disables all auto-configuration of the ObjectMapper.
If you provide any @Beans of type MappingJackson2HttpMessageConverter, they replace the default value in the MVC configuration. Also, a convenience bean of type HttpMessageConverters is provided (always available if you use the default MVC configuration). It has some useful methods to access the default and user-enhanced message converters.
See the “Section 75.4, “Customize the @ResponseBody Rendering”” section and the WebMvcAutoConfiguration source code for more details.
Spring uses HttpMessageConverters to render @ResponseBody (or responses from @RestController). You can contribute additional converters by adding beans of the appropriate type in a Spring Boot context. If a bean you add is of a type that would have been included by default anyway (such as MappingJackson2HttpMessageConverter for JSON conversions), it replaces the default value. A convenience bean of type HttpMessageConverters is provided and is always available if you use the default MVC configuration. It has some useful methods to access the default and user-enhanced message converters (For example, it can be useful if you want to manually inject them into a custom RestTemplate).
As in normal MVC usage, any WebMvcConfigurer beans that you provide can also contribute converters by overriding the configureMessageConverters method. However, unlike with normal MVC, you can supply only additional converters that you need (because Spring Boot uses the same mechanism to contribute its defaults). Finally, if you opt out of the Spring Boot default MVC configuration by providing your own @EnableWebMvc configuration, you can take control completely and do everything manually by using getMessageConverters from WebMvcConfigurationSupport.
See the WebMvcAutoConfiguration source code for more details.
Spring Boot embraces the Servlet 3 javax.servlet.http.Part API to support uploading files. By default, Spring Boot configures Spring MVC with a maximum size of 1MB per file and a maximum of 10MB of file data in a single request. You may override these values, the location to which intermediate data is stored (for example, to the /tmp directory), and the threshold past which data is flushed to disk by using the properties exposed in the MultipartProperties class. For example, if you want to specify that files be unlimited, set the spring.servlet.multipart.max-file-size property to -1.
The multipart support is helpful when you want to receive multipart encoded file data as a @RequestParam-annotated parameter of type MultipartFile in a Spring MVC controller handler method.
See the MultipartAutoConfiguration source for more details.
Spring Boot wants to serve all content from the root of your application (/) down. If you would rather map your own servlet to that URL, you can do it. However, you may lose some of the other Boot MVC features. To add your own servlet and map it to the root resource, declare a @Bean of type Servlet and give it the special bean name, dispatcherServlet. (You can also create a bean of a different type with that name if you want to switch it off and not replace it.)
The easiest way to take complete control over MVC configuration is to provide your own @Configuration with the @EnableWebMvc annotation. Doing so leaves all MVC configuration in your hands.
A ViewResolver is a core component of Spring MVC, translating view names in @Controller to actual View implementations. Note that ViewResolvers are mainly used in UI applications, rather than REST-style services (a View is not used to render a @ResponseBody). There are many implementations of ViewResolver to choose from, and Spring on its own is not opinionated about which ones you should use. Spring Boot, on the other hand, installs one or two for you, depending on what it finds on the classpath and in the application context. The DispatcherServlet uses all the resolvers it finds in the application context, trying each one in turn until it gets a result, so, if you add your own, you have to be aware of the order and in which position your resolver is added.
WebMvcAutoConfiguration adds the following ViewResolvers to your context:
- An
InternalResourceViewResolvernamed ‘defaultViewResolver’. This one locates physical resources that can be rendered by using theDefaultServlet(including static resources and JSP pages, if you use those). It applies a prefix and a suffix to the view name and then looks for a physical resource with that path in the servlet context (the defaults are both empty but are accessible for external configuration throughspring.mvc.view.prefixandspring.mvc.view.suffix). You can override it by providing a bean of the same type. - A
BeanNameViewResolvernamed ‘beanNameViewResolver’. This is a useful member of the view resolver chain and picks up any beans with the same name as theViewbeing resolved. It should not be necessary to override or replace it. - A
ContentNegotiatingViewResolvernamed ‘viewResolver’ is added only if there are actually beans of typeViewpresent. This is a ‘master’ resolver, delegating to all the others and attempting to find a match to the ‘Accept’ HTTP header sent by the client. There is a useful blog aboutContentNegotiatingViewResolverthat you might like to study to learn more, and you might also look at the source code for detail. You can switch off the auto-configuredContentNegotiatingViewResolverby defining a bean named ‘viewResolver’. - If you use Thymeleaf, you also have a
ThymeleafViewResolvernamed ‘thymeleafViewResolver’. It looks for resources by surrounding the view name with a prefix and suffix. The prefix isspring.thymeleaf.prefix, and the suffix isspring.thymeleaf.suffix. The values of the prefix and suffix default to ‘classpath:/templates/’ and ‘.html’, respectively. You can overrideThymeleafViewResolverby providing a bean of the same name. - If you use FreeMarker, you also have a
FreeMarkerViewResolvernamed ‘freeMarkerViewResolver’. It looks for resources in a loader path (which is externalized tospring.freemarker.templateLoaderPathand has a default value of ‘classpath:/templates/’) by surrounding the view name with a prefix and suffix. The prefix is externalized tospring.freemarker.prefix, and the suffix is externalized tospring.freemarker.suffix. The default values of the prefix and suffix are empty and ‘.ftl’, respectively. You can overrideFreeMarkerViewResolverby providing a bean of the same name. - If you use Groovy templates (actually, if
groovy-templatesis on your classpath), you also have aGroovyMarkupViewResolvernamed ‘groovyMarkupViewResolver’. It looks for resources in a loader path by surrounding the view name with a prefix and suffix (externalized tospring.groovy.template.prefixandspring.groovy.template.suffix). The prefix and suffix have default values of ‘classpath:/templates/’ and ‘.tpl’, respectively. You can overrideGroovyMarkupViewResolverby providing a bean of the same name.
For more detail, see the following sections:
Spring Boot offers a number of starters that work with HTTP clients. This section answers questions related to doing so.
As described in Section 33.1, “RestTemplate Customization”, you can use a RestTemplateCustomizer with RestTemplateBuilder to build a customizedRestTemplate. This is the recommended approach for creating a RestTemplate configured to use a proxy.
The exact details of the proxy configuration depend on the underlying client request factory that is being used. The following example configuresHttpComponentsClientRequestFactory with an HttpClient that uses a proxy for all hosts except 192.168.0.5:
static class ProxyCustomizer implements RestTemplateCustomizer { @Override public void customize(RestTemplate restTemplate) { HttpHost proxy = new HttpHost("proxy.example.com"); HttpClient httpClient = HttpClientBuilder.create() .setRoutePlanner(new DefaultProxyRoutePlanner(proxy) { @Override public HttpHost determineProxy(HttpHost target, HttpRequest request, HttpContext context) throws HttpException { if (target.getHostName().equals("192.168.0.5")) { return null; } return super.determineProxy(target, request, context); } }).build(); restTemplate.setRequestFactory( new HttpComponentsClientHttpRequestFactory(httpClient)); } }
Spring Boot has no mandatory logging dependency, except for the Commons Logging API, of which there are many implementations to choose from. To use Logback, you need to include it and jcl-over-slf4j (which implements the Commons Logging API) on the classpath. The simplest way to do that is through the starters, which all depend on spring-boot-starter-logging. For a web application, you need only spring-boot-starter-web, since it depends transitively on the logging starter. If you use Maven, the following dependency adds logging for you:
<dependency>
<groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency>
Spring Boot has a LoggingSystem abstraction that attempts to configure logging based on the content of the classpath. If Logback is available, it is the first choice.
If the only change you need to make to logging is to set the levels of various loggers, you can do so in application.properties by using the "logging.level" prefix, as shown in the following example:
logging.level.org.springframework.web=DEBUG
logging.level.org.hibernate=ERROR
You can also set the location of a file to which to write the log (in addition to the console) by using "logging.file".
To configure the more fine-grained settings of a logging system, you need to use the native configuration format supported by the LoggingSystem in question. By default, Spring Boot picks up the native configuration from its default location for the system (such as classpath:logback.xml for Logback), but you can set the location of the config file by using the "logging.config" property.
If you put a logback.xml in the root of your classpath, it is picked up from there (or from logback-spring.xml, to take advantage of the templating features provided by Boot). Spring Boot provides a default base configuration that you can include if you want to set levels, as shown in the following example:
<?xml version="1.0" encoding="UTF-8"?>
<configuration> <include resource="org/springframework/boot/logging/logback/base.xml"/> <logger name="org.springframework.web" level="DEBUG"/> </configuration>
If you look at base.xml in the spring-boot jar, you can see that it uses some useful System properties that the LoggingSystem takes care of creating for you:
${PID}: The current process ID.${LOG_FILE}: Whetherlogging.filewas set in Boot’s external configuration.${LOG_PATH}: Whetherlogging.path(representing a directory for log files to live in) was set in Boot’s external configuration.${LOG_EXCEPTION_CONVERSION_WORD}: Whetherlogging.exception-conversion-wordwas set in Boot’s external configuration.
Spring Boot also provides some nice ANSI color terminal output on a console (but not in a log file) by using a custom Logback converter. See the default base.xmlconfiguration for details.
If Groovy is on the classpath, you should be able to configure Logback with logback.groovy as well. If present, this setting is given preference.
If you want to disable console logging and write output only to a file, you need a custom logback-spring.xml that imports file-appender.xml but not console-appender.xml, as shown in the following example:
<?xml version="1.0" encoding="UTF-8"?>
<configuration> <include resource="org/springframework/boot/logging/logback/defaults.xml" /> <property name="LOG_FILE" value="${LOG_FILE:-${LOG_PATH:-${LOG_TEMP:-${java.io.tmpdir:-/tmp}}/}spring.log}"/> <include resource="org/springframework/boot/logging/logback/file-appender.xml" /> <root level="INFO"> <appender-ref ref="FILE" /> </root> </configuration>
You also need to add logging.file to your application.properties, as shown in the following example:
logging.file=myapplication.log
Spring Boot supports Log4j 2 for logging configuration if it is on the classpath. If you use the starters for assembling dependencies, you have to exclude Logback and then include log4j 2 instead. If you do not use the starters, you need to provide (at least) jcl-over-slf4j in addition to Log4j 2.
The simplest path is probably through the starters, even though it requires some jiggling with excludes. The following example shows how to set up the starters in Maven:
<dependency>
<groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter</artifactId> <exclusions> <exclusion> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-logging</artifactId> </exclusion> </exclusions> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-log4j2</artifactId> </dependency>
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| The Log4j starters gather together the dependencies for common logging requirements (such as having Tomcat use |
In addition to its default XML configuration format, Log4j 2 also supports YAML and JSON configuration files. To configure Log4j 2 to use an alternative configuration file format, add the appropriate dependencies to the classpath and name your configuration files to match your chosen file format, as shown in the following example:
| Format | Dependencies | File names |
|---|---|---|
| YAML |
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| JSON |
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Spring Boot includes a number of starters for working with data sources. This section answers questions related to doing so.
To configure your own DataSource, define a @Bean of that type in your configuration. Spring Boot reuses your DataSource anywhere one is required, including database initialization. If you need to externalize some settings, you can bind your DataSource to the environment (see “Section 24.7.1, “Third-party Configuration””).
The following example shows how to define a data source in a bean:
@Bean @ConfigurationProperties(prefix="app.datasource") public DataSource dataSource() { return new FancyDataSource(); }
The following example shows how to define a data source by setting properties:
app.datasource.url=jdbc:h2:mem:mydb
app.datasource.username=sa app.datasource.pool-size=30
Assuming that your FancyDataSource has regular JavaBean properties for the URL, the username, and the pool size, these settings are bound automatically before theDataSource is made available to other components. The regular database initialization also happens (so the relevant sub-set of spring.datasource.* can still be used with your custom configuration).
You can apply the same principle if you configure a custom JNDI DataSource, as shown in the following example:
@Bean(destroyMethod="") @ConfigurationProperties(prefix="app.datasource") public DataSource dataSource() throws Exception { JndiDataSourceLookup dataSourceLookup = new JndiDataSourceLookup(); return dataSourceLookup.getDataSource("java:comp/env/jdbc/YourDS"); }
Spring Boot also provides a utility builder class, called DataSourceBuilder, that can be used to create one of the standard data sources (if it is on the classpath). The builder can detect the one to use based on what’s available on the classpath. It also auto-detects the driver based on the JDBC URL.
The following example shows how to create a data source by using a DataSourceBuilder:
@Bean @ConfigurationProperties("app.datasource") public DataSource dataSource() { return DataSourceBuilder.create().build(); }
To run an app with that DataSource, all you need is the connection information. Pool-specific settings can also be provided. Check the implementation that is going to be used at runtime for more details.
The following example shows how to define a JDBC data source by setting properties:
app.datasource.url=jdbc:mysql://localhost/test
app.datasource.username=dbuser app.datasource.password=dbpass app.datasource.pool-size=30
However, there is a catch. Because the actual type of the connection pool is not exposed, no keys are generated in the metadata for your custom DataSource and no completion is available in your IDE (because the DataSource interface exposes no properties). Also, if you happen to have Hikari on the classpath, this basic setup does not work, because Hikari has no url property (but does have a jdbcUrl property). In that case, you must rewrite your configuration as follows:
app.datasource.jdbc-url=jdbc:mysql://localhost/test
app.datasource.username=dbuser app.datasource.password=dbpass app.datasource.maximum-pool-size=30
You can fix that by forcing the connection pool to use and return a dedicated implementation rather than DataSource. You cannot change the implementation at runtime, but the list of options will be explicit.
The following example shows how create a HikariDataSource with DataSourceBuilder:
@Bean @ConfigurationProperties("app.datasource") public HikariDataSource dataSource() { return DataSourceBuilder.create().type(HikariDataSource.class).build(); }
You can even go further by leveraging what DataSourceProperties does for you — that is, by providing a default embedded database with a sensible username and password if no URL is provided. You can easily initialize a DataSourceBuilder from the state of any DataSourceProperties object, so you could also inject the one Spring Boot creates automatically. However, that would split your configuration into two namespaces: url, username, password, type, and driver on spring.datasource and the rest on your custom namespace (app.datasource). To avoid that, you can redefine a custom DataSourceProperties on your custom namespace, as shown in the following example:
@Bean @Primary @ConfigurationProperties("app.datasource") public DataSourceProperties dataSourceProperties() { return new DataSourceProperties(); } @Bean @ConfigurationProperties("app.datasource") public HikariDataSource dataSource(DataSourceProperties properties) { return properties.initializeDataSourceBuilder().type(HikariDataSource.class) .build(); }
This setup puts you in sync with what Spring Boot does for you by default, except that a dedicated connection pool is chosen (in code) and its settings are exposed in the same namespace. Because DataSourceProperties is taking care of the url/jdbcUrl translation for you, you can configure it as follows:
app.datasource.url=jdbc:mysql://localhost/test
app.datasource.username=dbuser app.datasource.password=dbpass app.datasource.maximum-pool-size=30
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| Because your custom configuration chooses to go with Hikari, |
See “Section 29.1, “Configure a DataSource”” in the ‘Spring Boot features’ section and the DataSourceAutoConfiguration class for more details.
If you need to configure multiple data sources, you can apply the same tricks that are described in the previous section. You must, however, mark one of the DataSource instances as @Primary, because various auto-configurations down the road expect to be able to get one by type.
If you create your own DataSource, the auto-configuration backs off. In the following example, we provide the exact same feature set as the auto-configuration provides on the primary data source:
@Bean @Primary @ConfigurationProperties("app.datasource.foo") public DataSourceProperties fooDataSourceProperties() { return new DataSourceProperties(); } @Bean @Primary @ConfigurationProperties("app.datasource.foo") public DataSource fooDataSource() { return fooDataSourceProperties().initializeDataSourceBuilder().build(); } @Bean @ConfigurationProperties("app.datasource.bar") public BasicDataSource barDataSource() { return DataSourceBuilder.create().type(BasicDataSource.class).build(); }
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Both data sources are also bound for advanced customizations. For instance, you could configure them as follows:
app.datasource.foo.type=com.zaxxer.hikari.HikariDataSource
app.datasource.foo.maximum-pool-size=30 app.datasource.bar.url=jdbc:mysql://localhost/test app.datasource.bar.username=dbuser app.datasource.bar.password=dbpass app.datasource.bar.max-total=30
You can apply the same concept to the secondary DataSource as well, as shown in the following example:
@Bean @Primary @ConfigurationProperties("app.datasource.foo") public DataSourceProperties fooDataSourceProperties() { return new DataSourceProperties(); } @Bean @Primary @ConfigurationProperties("app.datasource.foo") public DataSource fooDataSource() { return fooDataSourceProperties().initializeDataSourceBuilder().build(); } @Bean @ConfigurationProperties("app.datasource.bar") public DataSourceProperties barDataSourceProperties() { return new DataSourceProperties(); } @Bean @ConfigurationProperties("app.datasource.bar") public DataSource barDataSource() { return barDataSourceProperties().initializeDataSourceBuilder().build(); }
The preceding example configures two data sources on custom namespaces with the same logic as Spring Boot would use in auto-configuration.
Spring Data can create implementations for you of @Repository interfaces of various flavors. Spring Boot handles all of that for you, as long as those @Repositoriesare included in the same package (or a sub-package) of your @EnableAutoConfiguration class.
For many applications, all you need is to put the right Spring Data dependencies on your classpath (there is a spring-boot-starter-data-jpa for JPA and aspring-boot-starter-data-mongodb for Mongodb) and create some repository interfaces to handle your @Entity objects. Examples are in the JPA sample and the Mongodb sample.
Spring Boot tries to guess the location of your @Repository definitions, based on the @EnableAutoConfiguration it finds. To get more control, use the @EnableJpaRepositories annotation (from Spring Data JPA).
Spring Boot tries to guess the location of your @Entity definitions, based on the @EnableAutoConfiguration it finds. To get more control, you can use the @EntityScan annotation, as shown in the following example:
@Configuration @EnableAutoConfiguration @EntityScan(basePackageClasses=City.class) public class Application { //... }
Spring Data JPA already provides some vendor-independent configuration options (such as those for SQL logging), and Spring Boot exposes those options and a few more for Hibernate as external configuration properties. Some of them are automatically detected according to the context so you should not have to set them.
The spring.jpa.hibernate.ddl-auto is a special case, because, depending on runtime conditions, it has different defaults. If an embedded database is used and no schema manager (such as Liquibase or Flyway) is handling the DataSource, it defaults to create-drop. In all other cases, it defaults to none.
The dialect to use is also automatically detected based on the current DataSource, but you can set spring.jpa.database yourself if you want to be explicit and bypass that check on startup.
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| Specifying a |
The most common options to set are shown in the following example:
spring.jpa.hibernate.naming.physical-strategy=com.example.MyPhysicalNamingStrategy spring.jpa.show-sql=true
In addition, all properties in spring.jpa.properties.* are passed through as normal JPA properties (with the prefix stripped) when the local EntityManagerFactory is created.
Hibernate uses two different naming strategies to map names from the object model to the corresponding database names. The fully qualified class name of the physical and the implicit strategy implementations can be configured by setting the spring.jpa.hibernate.naming.physical-strategy andspring.jpa.hibernate.naming.implicit-strategy properties, respectively.
By default, Spring Boot configures the physical naming strategy with SpringPhysicalNamingStrategy. This implementation provides the same table structure as Hibernate 4: all dots are replaced by underscores and camel casing is replaced by underscores as well. By default, all table names are generated in lower case, but it is possible to override that flag if your schema requires it.
For example, a TelephoneNumber entity is mapped to the telephone_number table.
If you prefer to use Hibernate 5’s default instead, set the following property:
spring.jpa.hibernate.naming.physical-strategy=org.hibernate.boot.model.naming.PhysicalNamingStrategyStandardImpl
See HibernateJpaAutoConfiguration and JpaBaseConfiguration for more details.
To take full control of the configuration of the EntityManagerFactory, you need to add a @Bean named ‘entityManagerFactory’. Spring Boot auto-configuration switches off its entity manager in the presence of a bean of that type.
Even if the default EntityManagerFactory works fine, you need to define a new one. Otherwise, the presence of the second bean of that type switches off the default. To make it easy to do, you can use the convenient EntityManagerBuilder provided by Spring Boot. Alternatively, you can just theLocalContainerEntityManagerFactoryBean directly from Spring ORM, as shown in the following example:
// add two data sources configured as above
@Bean
public LocalContainerEntityManagerFactoryBean customerEntityManagerFactory( EntityManagerFactoryBuilder builder) { return builder .dataSource(customerDataSource()) .packages(Customer.class) .persistenceUnit("customers") .build(); } @Bean public LocalContainerEntityManagerFactoryBean orderEntityManagerFactory( EntityManagerFactoryBuilder builder) { return builder .dataSource(orderDataSource()) .packages(Order.class) .persistenceUnit("orders") .build(); }
The configuration above almost works on its own. To complete the picture, you need to configure TransactionManagers for the two EntityManagers as well. One of them could be picked up by the default JpaTransactionManager in Spring Boot if you mark it as @Primary. The other would have to be explicitly injected into a new instance. Alternatively, you might be able to use a JTA transaction manager that spans both.
If you are using Spring Data, you need to configure @EnableJpaRepositories accordingly, as shown in the following example:
@Configuration @EnableJpaRepositories(basePackageClasses = Customer.class, entityManagerFactoryRef = "customerEntityManagerFactory") public class CustomerConfiguration { ... } @Configuration @EnableJpaRepositories(basePackageClasses = Order.class, entityManagerFactoryRef = "orderEntityManagerFactory") public class OrderConfiguration { ... }
Spring does not require the use of XML to configure the JPA provider, and Spring Boot assumes you want to take advantage of that feature. If you prefer to use persistence.xml, you need to define your own @Bean of type LocalEntityManagerFactoryBean (with an ID of ‘entityManagerFactory’) and set the persistence unit name there.
See JpaBaseConfiguration for the default settings.
Spring Data JPA and Spring Data Mongo can both automatically create Repository implementations for you. If they are both present on the classpath, you might have to do some extra configuration to tell Spring Boot which one (or both) you want to create repositories for you. The most explicit way to do that is to use the standard Spring Data @EnableJpaRepositories and @EnableMongoRepositories annotations and provide the location of your Repository interfaces.
There are also flags (spring.data.*.repositories.enabled) that you can use to switch the auto-configured repositories on and off in external configuration. Doing so is useful, for instance, in case you want to switch off the Mongo repositories and still use the auto-configured MongoTemplate.
The same obstacle and the same features exist for other auto-configured Spring Data repository types (Elasticsearch, Solr, and others). To work with them, change the names of the annotations and flags accordingly.
Spring Data REST can expose the Repository implementations as REST endpoints for you, provided Spring MVC has been enabled for the application.
Spring Boot exposes a set of useful properties (from the spring.data.rest namespace) that customize the RepositoryRestConfiguration. If you need to provide additional customization, you should use a RepositoryRestConfigurer bean.
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| If you do not specify any order on your custom |
If you want to configure a component that JPA uses, then you need to ensure that the component is initialized before JPA. When the component is auto-configured, Spring Boot takes care of this for you. For example, when Flyway is auto-configured, Hibernate is configured to depend upon Flyway so that Flyway has a chance to initialize the database before Hibernate tries to use it.
If you are configuring a component yourself, you can use an EntityManagerFactoryDependsOnPostProcessor subclass as a convenient way of setting up the necessary dependencies. For example, if you use Hibernate Search with Elasticsearch as its index manager, any EntityManagerFactory beans must be configured to depend on the elasticsearchClient bean, as shown in the following example:
/**
* {@link EntityManagerFactoryDependsOnPostProcessor} that ensures that
* {@link EntityManagerFactory} beans depend on the {@code elasticsearchClient} bean.
*/
@Configuration
static class ElasticsearchJpaDependencyConfiguration extends EntityManagerFactoryDependsOnPostProcessor { ElasticsearchJpaDependencyConfiguration() { super("elasticsearchClient"); } }
An SQL database can be initialized in different ways depending on what your stack is. Of course, you can also do it manually, provided the database is a separate process.
JPA has features for DDL generation, and these can be set up to run on startup against the database. This is controlled through two external properties:
spring.jpa.generate-ddl(boolean) switches the feature on and off and is vendor independent.spring.jpa.hibernate.ddl-auto(enum) is a Hibernate feature that controls the behavior in a more fine-grained way. This feature is described in more detail later in the document.
You can set spring.jpa.hibernate.ddl-auto explicitly and the standard Hibernate property values are none, validate, update, create, and create-drop. Spring Boot chooses a default value for you based on whether it thinks your database is embedded. It defaults to create-drop if no schema manager has been detected or none in all other cases. An embedded database is detected by looking at the Connection type. hsqldb, h2, and derby are embedded, and others are not. Be careful when switching from in-memory to a ‘real’ database that you do not make assumptions about the existence of the tables and data in the new platform. You either have to set ddl-auto explicitly or use one of the other mechanisms to initialize the database.
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| You can output the schema creation by enabling the |
In addition, a file named import.sql in the root of the classpath is executed on startup if Hibernate creates the schema from scratch (that is, if the ddl-auto property is set to create or create-drop). This can be useful for demos and for testing if you are careful but is probably not something you want to be on the classpath in production. It is a Hibernate feature (and has nothing to do with Spring).
Spring Boot can automatically create the schema (DDL scripts) of your DataSource and initialize it (DML scripts). It loads SQL from the standard root classpath locations: schema.sql and data.sql, respectively. In addition, Spring Boot processes the schema-${platform}.sql and data-${platform}.sql files (if present), where platform is the value of spring.datasource.platform. This allows you to switch to database-specific scripts if necessary. For example, you might choose to set it to the vendor name of the database (hsqldb, h2, oracle, mysql, postgresql, and so on).
Spring Boot automatically creates the schema of an embedded DataSource. This behavior can be customized by using the spring.datasource.initialization-mode property (and it can also be always or never).
By default, Spring Boot enables the fail-fast feature of the Spring JDBC initializer, so, if the scripts cause exceptions, the application fails to start. You can tune that behavior by setting spring.datasource.continue-on-error.
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| In a JPA-based app, you can choose to let Hibernate create the schema or use |
If you use Spring Batch, it comes pre-packaged with SQL initialization scripts for most popular database platforms. Spring Boot can detect your database type and execute those scripts on startup. If you use an embedded database, this happens by default. You can also enable it for any database type, as shown in the following example:
spring.batch.initialize-schema=always
You can also switch off the initialization explicitly by setting spring.batch.initialize-schema=never.
Spring Boot supports two higher-level migration tools: Flyway and Liquibase.
To automatically run Flyway database migrations on startup, add the org.flywaydb:flyway-core to your classpath.
The migrations are scripts in the form V<VERSION>__<NAME>.sql (with <VERSION> an underscore-separated version, such as ‘1’ or ‘2_1’). By default, they live in a folder called classpath:db/migration, but you can modify that location by setting spring.flyway.locations. You can also add a special {vendor} placeholder to use vendor-specific scripts. Assume the following:
spring.flyway.locations=db/migration/{vendor}
Rather than using db/migration, the preceding configuration sets the folder to use according to the type of the database (such as db/migration/mysql for MySQL). The list of supported database are available in DatabaseDriver.
See the Flyway class from flyway-core for details of available settings such as schemas and others. In addition, Spring Boot provides a small set of properties (inFlywayProperties) that can be used to disable the migrations or switch off the location checking. Spring Boot calls Flyway.migrate() to perform the database migration. If you would like more control, provide a @Bean that implements FlywayMigrationStrategy.
Flyway supports SQL and Java callbacks. To use SQL-based callbacks, place the callback scripts in the classpath:db/migration folder. To use Java-based callbacks, create one or more beans that implement FlywayCallback or, preferably, extend BaseFlywayCallback. Any such beans are automatically registered with Flyway. They can be ordered by using @Order or by implementing Ordered.
By default, Flyway autowires the (@Primary) DataSource in your context and uses that for migrations. If you like to use a different DataSource, you can create one and mark its @Bean as @FlywayDataSource. If you do so and want two data sources, remember to create another one and mark it as @Primary. Alternatively, you can use Flyway’s native DataSource by setting spring.flyway.[url,user,password] in external properties.
There is a Flyway sample so that you can see how to set things up.
You can also use Flyway to provide data for specific scenarios. For example, you can place test-specific migrations in src/test/resources and they are run only when your application starts for testing. If you want to be more sophisticated, you can use profile-specific configuration to customize spring.flyway.locations so that certain migrations run only when a particular profile is active. For example, in application-dev.properties, you might specify the following setting:
spring.flyway.locations=classpath:/db/migration,classpath:/dev/db/migration
With that setup, migrations in dev/db/migration run only when the dev profile is active.
To automatically run Liquibase database migrations on startup, add the org.liquibase:liquibase-core to your classpath.
By default, the master change log is read from db/changelog/db.changelog-master.yaml, but you can change the location by setting spring.liquibase.change-log. In addition to YAML, Liquibase also supports JSON, XML, and SQL change log formats.
By default, Liquibase autowires the (@Primary) DataSource in your context and uses that for migrations. If you like to use a different DataSource, you can create one and mark its @Bean as @LiquibaseDataSource. If you do so and you want two data sources, remember to create another one and mark it as @Primary. Alternatively, you can use Liquibase’s native DataSource by setting spring.liquibase.[url,user,password] in external properties.
See LiquibaseProperties for details about available settings such as contexts, the default schema, and others.
There is a Liquibase sample so that you can see how to set things up.
Spring Boot offers a number of starters that include messaging. This section answers questions that arise from using messaging with Spring Boot.
If your JMS broker does not support transacted session, you have to disable the support of transactions altogether. If you create your own JmsListenerContainerFactory, there is nothing to do, since, by default it cannot be transacted. If you want to use the DefaultJmsListenerContainerFactoryConfigurer to reuse Spring Boot’s default, you can disable transacted session, as follows:
@Bean public DefaultJmsListenerContainerFactory jmsListenerContainerFactory( ConnectionFactory connectionFactory, DefaultJmsListenerContainerFactoryConfigurer configurer) { DefaultJmsListenerContainerFactory listenerFactory = new DefaultJmsListenerContainerFactory(); configurer.configure(listenerFactory, connectionFactory); listenerFactory.setTransactionManager(null); listenerFactory.setSessionTransacted(false); return listenerFactory; }
The preceding example overrides the default factory, and it should be applied to any other factory that your application defines, if any.
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| By default, batch applications require a |
Spring Batch auto-configuration is enabled by adding @EnableBatchProcessing (from Spring Batch) somewhere in your context.
By default, it executes all Jobs in the application context on startup (see JobLauncherCommandLineRunner for details). You can narrow down to a specific job or jobs by specifying spring.batch.job.names (comma-separated job name patterns).
If the application context includes a JobRegistry, the jobs in spring.batch.job.names are looked up in the registry instead of being autowired from the context. This is a common pattern with more complex systems, where multiple jobs are defined in child contexts and registered centrally.
See BatchAutoConfiguration and @EnableBatchProcessing for more details.
Spring Boot includes the Spring Boot Actuator. This section answers questions that often arise from its use.
In a standalone application, the Actuator HTTP port defaults to the same as the main HTTP port. To make the application listen on a different port, set the external property, management.server.port. To listen on a completely different network address (such as when you have an internal network for management and an external one for user applications), you can also set management.server.address to a valid IP address to which the server is able to bind.
For more detail, see the ManagementServerProperties source code and “Section 50.2, “Customizing the Management Server Port”” in the ‘Production-ready features’ section.
Spring Boot installs a ‘whitelabel’ error page that you see in a browser client if you encounter a server error (machine clients consuming JSON and other media types should see a sensible response with the right error code).
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| Set |
Overriding the error page with your own depends on the templating technology that you use. For example, if you use Thymeleaf, you can add an error.html template. If you use FreeMarker, you can add an error.ftl template. In general, you need a View that resolves with a name of error or a @Controller that handles the /error path. Unless you replaced some of the default configuration, you should find a BeanNameViewResolver in your ApplicationContext, so a @Bean named error would be a simple way of doing that. See ErrorMvcAutoConfiguration for more options.
See also the section on “Error Handling” for details of how to register handlers in the servlet container.
Actuator HTTP endpoints are available only for Spring MVC-based applications. If you want to use Jersey and still use the actuator, you need to enable Spring MVC (by depending on spring-boot-starter-web, for example). By default, both Jersey and the Spring MVC dispatcher servlet are mapped to the same path (/). You need to change the path for one of them (by configuring server.servlet.path for Spring MVC or spring.jersey.application-path for Jersey). For example, if you addserver.servlet.path=/system into application.properties, the actuator HTTP endpoints are available under /system.
If you define a @Configuration with @EnableWebSecurity anywhere in your application, it switches off the default webapp security settings in Spring Boot (but leaves the Actuator’s security enabled). To tweak the defaults try setting properties in security.* (see SecurityProperties for details of available settings) and the SECURITY section of “Common Application Properties”.
If you provide a @Bean of type AuthenticationManager, the default one is not created, so you have the full feature set of Spring Security available (such as various authentication options).
Spring Security also provides a convenient AuthenticationManagerBuilder, which can be used to build an AuthenticationManager with common options. The recommended way to use this in a webapp is to inject it into a void method in a WebSecurityConfigurerAdapter, as shown in the following example:
@Configuration public class SecurityConfiguration extends WebSecurityConfigurerAdapter { @Autowired public void configureGlobal(AuthenticationManagerBuilder auth) throws Exception { auth.inMemoryAuthentication() .withUser("barry").password("password").roles("USER"); // ... etc. } // ... other stuff for application security }
You get the best results if you put this in a nested class or a standalone class (that is, not mixed in with a lot of other @Beans that might be allowed to influence the order of instantiation). The secure web sample is a useful template to follow.
If you experience instantiation issues (for example, when using JDBC or JPA for the user detail store), it might be worth extracting the AuthenticationManagerBuilder callback into a GlobalAuthenticationConfigurerAdapter (in the init() method so that it happens before the authentication manager is needed elsewhere), as shown in the following example:
@Configuration public class AuthenticationManagerConfiguration extends GlobalAuthenticationConfigurerAdapter { @Override public void init(AuthenticationManagerBuilder auth) { auth.inMemoryAuthentication() // ... etc. } }
Ensuring that all your main endpoints are only available over HTTPS is an important chore for any application. If you use Tomcat as a servlet container, then Spring Boot adds Tomcat’s own RemoteIpValve automatically if it detects some environment settings, and you should be able to rely on the HttpServletRequest to report whether it is secure or not (even downstream of a proxy server that handles the real SSL termination). The standard behavior is determined by the presence or absence of certain request headers (x-forwarded-for and x-forwarded-proto), whose names are conventional, so it should work with most front-end proxies. You can switch on the valve by adding some entries to application.properties, as shown in the following example:
server.tomcat.remote-ip-header=x-forwarded-for
server.tomcat.protocol-header=x-forwarded-proto
(The presence of either of those properties switches on the valve. Alternatively, you can add the RemoteIpValve yourself by adding a TomcatServletWebServerFactory bean.)
Spring Security can also be configured to require a secure channel for all (or some) requests. To switch that on in a Spring Boot application, setsecurity.require_ssl to true in application.properties.
Spring Boot supports hot swapping. This section answers questions about how it works.
There are several options for hot reloading. The recommended approach is to use spring-boot-devtools, as it provides additional development-time features, such as support for fast application restarts and LiveReload as well as sensible development-time configuration (such as template caching). Devtools works by monitoring the classpath for changes. This means that static resource changes must be "built" for the change to take affect. By default, this happens automatically in Eclipse when you save your changes. In IntelliJ IDEA, Make Project triggers the necessary build. Due to the default restart exclusions, changes to static resources do not trigger a restart of your application. They do, however, trigger a live reload.
Alternatively, running in an IDE (especially with debugging on) is a good way to do development (all modern IDEs allow reloading of static resources and usually also hot-swapping of Java class changes).
Finally, the Maven and Gradle plugins can be configured (see the addResources property) to support running from the command line with reloading of static files directly from source. You can use that with an external css/js compiler process if you are writing that code with higher-level tools.
Most of the templating technologies supported by Spring Boot include a configuration option to disable caching (described later in this document). If you use thespring-boot-devtools module, these properties are automatically configured for you at development time.
If you use Thymeleaf, set spring.thymeleaf.cache to false. See ThymeleafAutoConfiguration for other Thymeleaf customization options.
If you use FreeMarker, set spring.freemarker.cache to false. See FreeMarkerAutoConfiguration for other FreeMarker customization options.
If you use Groovy templates, set spring.groovy.template.cache to false. See GroovyTemplateAutoConfiguration for other Groovy customization options.
The spring-boot-devtools module includes support for automatic application restarts. While not as fast as technologies such as JRebel it is usually significantly faster than a “cold start”. You should probably give it a try before investigating some of the more complex reload options discussed later in this document.
For more details, see the Chapter 20, Developer Tools section.
Spring Boot includes build plugins for Maven and Gradle. This section answers common questions about these plugins.
Both the Maven plugin and the Gradle plugin allow generating build information containing the coordinates, name, and version of the project. The plugins can also be configured to add additional properties through configuration. When such a file is present, Spring Boot auto-configures a BuildProperties bean.
To generate build information with Maven, add an execution for the build-info goal, as shown in the following example:
<build>
<plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> <version>2.0.0.BUILD-SNAPSHOT</version> <executions> <execution> <goals> <goal>build-info</goal> </goals> </execution> </executions> </plugin> </plugins> </build>
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| See the Spring Boot Maven Plugin documentation for more details. |
The following example does the same with Gradle:
springBoot {
buildInfo()
}
Additional properties can be added by using the DSL, as shown in the following example:
springBoot {
buildInfo {
additionalProperties = [
'foo': 'bar' ] } }
Both Maven and Gradle allow generating a git.properties file containing information about the state of your git source code repository when the project was built.
For Maven users, the spring-boot-starter-parent POM includes a pre-configured plugin to generate a git.properties file. To use it, add the following declaration to your POM:
<build>
<plugins> <plugin> <groupId>pl.project13.maven</groupId> <artifactId>git-commit-id-plugin</artifactId> </plugin> </plugins> </build>
Gradle users can achieve the same result by using the gradle-git-properties plugin, as shown in the following example:
plugins {
id "com.gorylenko.gradle-git-properties" version "1.4.17" }
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| The commit time in |
If you use a Maven build that inherits directly or indirectly from spring-boot-dependencies (for instance spring-boot-starter-parent) but you want to override a specific third-party dependency, you can add appropriate <properties> elements. Browse the spring-boot-dependencies POM for a complete list of properties. For example, to pick a different slf4j version you would add the following property:
<properties>
<slf4j.version>1.7.5<slf4j.version> </properties>
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| Doing so only works if your Maven project inherits (directly or indirectly) from |
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| Each Spring Boot release is designed and tested against a specific set of third-party dependencies. Overriding versions may cause compatibility issues. |
The spring-boot-maven-plugin can be used to create an executable ‘fat’ JAR. If you are using the spring-boot-starter-parent POM, you can simply declare the plugin and your jars are repackaged as follows:
<build>
<plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build>
If you do not use the parent POM, you can still use the plugin. However, you must additionally add an <executions> section, as follows:
<build>
<plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> <version>2.0.0.BUILD-SNAPSHOT</version> <executions> <execution> <goals> <goal>repackage</goal> </goals> </execution> </executions> </plugin> </plugins> </build>
See the plugin documentation for full usage details.
Like a war file, a Spring Boot application is not intended to be used as a dependency. If your application contains classes that you want to share with other projects, the recommended approach is to move that code into a separate module. The separate module can then be depended upon by your application and other projects.
If you cannot rearrange your code as recommended above, Spring Boot’s Maven and Gradle plugins must be configured to produce a separate artifact that is suitable for use as a dependency. The executable archive cannot be used as a dependency as the executable jar format packages application classes in BOOT-INF/classes. This means that they cannot be found when the executable jar is used as a dependency.
To produce the two artifacts, one that can be used as a dependency and one that is executable, a classifier must be specified. This classifier is applied to the name of the executable archive, leaving the default archive for use as a dependency.
To configure a classifier of exec in Maven, the following configuration can be used:
<build>
<plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> <configuration> <classifier>exec</classifier> </configuration> </plugin> </plugins> </build>
Most nested libraries in an executable jar do not need to be unpacked in order to run. However, certain libraries can have problems. For example, JRuby includes its own nested jar support, which assumes that the jruby-complete.jar is always directly available as a file in its own right.
To deal with any problematic libraries, you can flag that specific nested jars should be automatically unpacked to the ‘temp folder’ when the executable jar first runs.
For example, to indicate that JRuby should be flagged for unpacking by using the Maven Plugin, you would add the following configuration:
<build>
<plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> <configuration> <requiresUnpack> <dependency> <groupId>org.jruby</groupId> <artifactId>jruby-complete</artifactId> </dependency> </requiresUnpack> </configuration> </plugin> </plugins> </build>
Often, if you have an executable and a non-executable jar as build products, the executable version has additional configuration files that are not needed in a library jar. For example, the application.yml configuration file might by excluded from the non-executable JAR.
In Maven, the executable jar must be the main artifact and you can add a classified jar for the library, as follows:
<build>
<plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> <plugin> <artifactId>maven-jar-plugin</artifactId> <executions> <execution> <id>lib</id> <phase>package</phase> <goals> <goal>jar</goal> </goals> <configuration> <classifier>lib</classifier> <excludes> <exclude>application.yml</exclude> </excludes> </configuration> </execution> </executions> </plugin> </plugins> </build>
To attach a remote debugger to a Spring Boot application that was started with Maven, you can use the jvmArguments property of the maven plugin.
See this example for more details.
To build with Ant, you need to grab dependencies, compile, and then create a jar or war archive. To make it executable, you can either use the spring-boot-antlibmodule or you can follow these instructions:
- If you are building a jar, package the application’s classes and resources in a nested
BOOT-INF/classesdirectory. If you are building a war, package the application’s classes in a nestedWEB-INF/classesdirectory as usual. - Add the runtime dependencies in a nested
BOOT-INF/libdirectory for a jar orWEB-INF/libfor a war. Remember not to compress the entries in the archive. - Add the
provided(embedded container) dependencies in a nestedBOOT-INF/libdirectory for a jar orWEB-INF/lib-providedfor a war. Remember not to compress the entries in the archive. - Add the
spring-boot-loaderclasses at the root of the archive (so that theMain-Classis available). - Use the appropriate launcher (such as
JarLauncherfor a jar file) as aMain-Classattribute in the manifest and specify the other properties it needs as manifest entries — principally, by setting aStart-Classproperty.
The following example shows how to build an executable archive with Ant:
<target name="build" depends="compile"> <jar destfile="target/${ant.project.name}-${spring-boot.version}.jar" compress="false"> <mappedresources> <fileset dir="target/classes" /> <globmapper from="*" to="BOOT-INF/classes/*"/> </mappedresources> <mappedresources> <fileset dir="src/main/resources" erroronmissingdir="false"/> <globmapper from="*" to="BOOT-INF/classes/*"/> </mappedresources> <mappedresources> <fileset dir="${lib.dir}/runtime" /> <globmapper from="*" to="BOOT-INF/lib/*"/> </mappedresources> <zipfileset src="${lib.dir}/loader/spring-boot-loader-jar-${spring-boot.version}.jar" /> <manifest> <attribute name="Main-Class" value="org.springframework.boot.loader.JarLauncher" /> <attribute name="Start-Class" value="${start-class}" /> </manifest> </jar> </target>
The Ant Sample has a build.xml file with a manual task that should work if you run it with the following command:
$ ant -lib <folder containing ivy-2.2.jar> clean manual
Then you can run the application with the following command:
$ java -jar target/*.jar
Spring Boot supports traditional deployment as well as more modern forms of deployment. This section answers common questions about traditional deployment.
The first step in producing a deployable war file is to provide a SpringBootServletInitializer subclass and override its configure method. Doing so makes use of Spring Framework’s Servlet 3.0 support and lets you configure your application when it is launched by the servlet container. Typically, you should update your application’s main class to extend SpringBootServletInitializer, as shown in the following example:
@SpringBootApplication public class Application extends SpringBootServletInitializer { @Override protected SpringApplicationBuilder configure(SpringApplicationBuilder application) { return application.sources(Application.class); } public static void main(String[] args) throws Exception { SpringApplication.run(Application.class, args); } }
The next step is to update your build configuration such that your project produces a war file rather than a jar file. If you use Maven and spring-boot-starter-parent(which configures Maven’s war plugin for you) all you need to do is to modify pom.xml to change the packaging to war, as follows:
<packaging>war</packaging>
If you use Gradle, you need to modify build.gradle to apply the war plugin to the project, as follows:
apply plugin: 'war'
The final step in the process is to ensure that the embedded servlet container does not interfere with the servlet container to which the war file is deployed. To do so, you need to mark the embedded servlet container dependency as being provided.
If you use Maven, the following example marks the servlet container (Tomcat, in this case) as being provided:
<dependencies>
<!-- … --> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-tomcat</artifactId> <scope>provided</scope> </dependency> <!-- … --> </dependencies>
If you use Gradle, the following example marks the servlet container (Tomcat, in this case) as being provided:
dependencies {
// …
providedRuntime 'org.springframework.boot:spring-boot-starter-tomcat' // … }
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If you use the Spring Boot build tools, marking the embedded servlet container dependency as provided produces an executable war file with the provided dependencies packaged in a lib-provided directory. This means that, in addition to being deployable to a servlet container, you can also run your application by using java -jaron the command line.
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| Take a look at Spring Boot’s sample applications for a Maven-based example of the previously described configuration. |
Older Servlet containers do not have support for the ServletContextInitializer bootstrap process used in Servlet 3.0. You can still use Spring and Spring Boot in these containers but you are going to need to add a web.xml to your application and configure it to load an ApplicationContext via a DispatcherServlet.
For a non-web application, it should be easy to convert an existing Spring application to a Spring Boot application. To do so, throw away the code that creates yourApplicationContext and replace it with calls to SpringApplication or SpringApplicationBuilder. Spring MVC web applications are generally amenable to first creating a deployable war application and then migrating it later to an executable war or jar. See the Getting Started Guide on Converting a jar to a war.
To create a deployable war by extending SpringBootServletInitializer (for example, in a class called Application) and add the Spring Boot @SpringBootApplication annotation, use code similar to that shown in the following example:
@SpringBootApplication public class Application extends SpringBootServletInitializer { @Override protected SpringApplicationBuilder configure(SpringApplicationBuilder application) { // Customize the application or call application.sources(...) to add sources // Since our example is itself a @Configuration class (via @SpringBootApplication) // we actually don't need to override this method. return application; } }
Remember that, whatever you put in the sources is merely a Spring ApplicationContext. Normally, anything that already works should work here. There might be some beans you can remove later and let Spring Boot provide its own defaults for them, but it should be possible to get something working before you need to do that.
Static resources can be moved to /public (or /static or /resources or /META-INF/resources) in the classpath root. The same applies to messages.properties (which Spring Boot automatically detects in the root of the classpath).
Vanilla usage of Spring DispatcherServlet and Spring Security should require no further changes. If you have other features in your application (for instance, using other servlets or filters), you may need to add some configuration to your Application context, by replacing those elements from the web.xml as follows:
- A
@Beanof typeServletorServletRegistrationBeaninstalls that bean in the container as if it were a<servlet/>and<servlet-mapping/>inweb.xml. - A
@Beanof typeFilterorFilterRegistrationBeanbehaves similarly (as a<filter/>and<filter-mapping/>). - An
ApplicationContextin an XML file can be added through an@ImportResourcein yourApplication. Alternatively, simple cases where annotation configuration is heavily used already can be recreated in a few lines as@Beandefinitions.
Once the war file is working, you can make it executable by adding a main method to your Application, as shown in the following example:
public static void main(String[] args) { SpringApplication.run(Application.class, args); }
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| If you intend to start your application as a war or as an executable application, you need to share the customizations of the builder in a method that is both available to the @SpringBootApplication public class Application extends SpringBootServletInitializer { @Override protected SpringApplicationBuilder configure(SpringApplicationBuilder builder) { return configureApplication(builder); } public static void main(String[] args) { configureApplication(new SpringApplicationBuilder()).run(args); } private static SpringApplicationBuilder configureApplication(SpringApplicationBuilder builder) { return builder.sources(Application.class).bannerMode(Banner.Mode.OFF); } } |
Applications can fall into more than one category:
- Servlet 3.0+ applications with no
web.xml. - Applications with a
web.xml. - Applications with a context hierarchy.
- Applications without a context hierarchy.
All of these should be amenable to translation, but each might require slightly different techniques.
Servlet 3.0+ applications might translate pretty easily if they already use the Spring Servlet 3.0+ initializer support classes. Normally, all the code from an existingWebApplicationInitializer can be moved into a SpringBootServletInitializer. If your existing application has more than one ApplicationContext (for example, if it uses AbstractDispatcherServletInitializer) then you might be able to combine all your context sources into a single SpringApplication. The main complication you might encounter is if combining does not work and you need to maintain the context hierarchy. See the entry on building a hierarchy for examples. An existing parent context that contains web-specific features usually needs to be broken up so that all the ServletContextAware components are in the child context.
Applications that are not already Spring applications might be convertible to Spring Boot applications, and the previously mentioned guidance may help. However, you may yet encounter problems. In that case, we suggest asking questions on Stack Overflow with a tag of spring-boot.
To deploy a Spring Boot application to WebLogic, you must ensure that your servlet initializer directly implements WebApplicationInitializer (even if you extend from a base class that already implements it).
A typical initializer for WebLogic should resemble the following example:
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.context.web.SpringBootServletInitializer; import org.springframework.web.WebApplicationInitializer; @SpringBootApplication public class MyApplication extends SpringBootServletInitializer implements WebApplicationInitializer { }
If you use Logback, you also need to tell WebLogic to prefer the packaged version rather than the version that was pre-installed with the server. You can do so by adding a WEB-INF/weblogic.xml file with the following contents:
<?xml version="1.0" encoding="UTF-8"?>
<wls:weblogic-web-app xmlns:wls="http://xmlns.oracle.com/weblogic/weblogic-web-app" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/ejb-jar_3_0.xsd http://xmlns.oracle.com/weblogic/weblogic-web-app http://xmlns.oracle.com/weblogic/weblogic-web-app/1.4/weblogic-web-app.xsd"> <wls:container-descriptor> <wls:prefer-application-packages> <wls:package-name>org.slf4j</wls:package-name> </wls:prefer-application-packages> </wls:container-descriptor> </wls:weblogic-web-app>
Spring Boot uses Servlet 3.0 APIs to initialize the ServletContext (register Servlets and so on), so you cannot use the same application in a Servlet 2.5 container. It is, however, possible to run a Spring Boot application on an older container with some special tools. If you include org.springframework.boot:spring-boot-legacyas a dependency (maintained separately to the core of Spring Boot and currently available at 1.0.2.RELEASE), all you should need to do is create a web.xml and declare a context listener to create the application context and your filters and servlets. The context listener is a special purpose one for Spring Boot, but the rest of it is normal for a Spring application in Servlet 2.5. The following Maven example shows how to set up a Spring Boot project to run in a Servlet 2.5 container:
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"> <context-param> <param-name>contextConfigLocation</param-name> <param-value>demo.Application</param-value> </context-param> <listener> <listener-class>org.springframework.boot.legacy.context.web.SpringBootContextLoaderListener</listener-class> </listener> <filter> <filter-name>metricsFilter</filter-name> <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class> </filter> <filter-mapping> <filter-name>metricsFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <servlet> <servlet-name>appServlet</servlet-name> <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class> <init-param> <param-name>contextAttribute</param-name> <param-value>org.springframework.web.context.WebApplicationContext.ROOT</param-value> </init-param> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>appServlet</servlet-name> <url-pattern>/</url-pattern> </servlet-mapping> </web-app>
In the preceding example, we use a single application context (the one created by the context listener) and attach it to the DispatcherServlet by using an initparameter. This is normal in a Spring Boot application (you normally only have one application context).
By default, the Spring Boot starter (spring-boot-starter-data-redis) uses Lettuce. You need to exclude that dependency and include the Jedis one instead. Spring Boot manages these dependencies to help make this process as easy as possible.
The following example shows how to do so in Maven:
<dependency>
<groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-redis</artifactId> <exclusions> <exclusion> <groupId>io.lettuce</groupId> <artifactId>lettuce-core</artifactId> </exclusion> </exclusions> </dependency> <dependency> <groupId>redis.clients</groupId> <artifactId>jedis</artifactId> </dependency>
The following example shows how to do so in Gradle:
configurations {
compile.exclude module: "lettuce"
}
dependencies {
compile("redis.clients:jedis") // ... }
Various properties can be specified inside your application.properties/application.yml file or as command line switches. This section provides a list of common Spring Boot properties and references to the underlying classes that consume them.
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| Property contributions can come from additional jar files on your classpath so you should not consider this an exhaustive list. It is also perfectly legit to define your own properties. |
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| This sample file is meant as a guide only. Do not copy/paste the entire content into your application; rather pick only the properties that you need. |
# ===================================================================
# COMMON SPRING BOOT PROPERTIES # # This sample file is provided as a guideline. Do NOT copy it in its # entirety to your own application. ^^^ # =================================================================== # ---------------------------------------- # CORE PROPERTIES # ---------------------------------------- # BANNER banner.charset=UTF-8 # Banner file encoding. banner.location=classpath:banner.txt # Banner file location. banner.image.location=classpath:banner.gif # Banner image file location (jpg/png can also be used). banner.image.width= # Width of the banner image in chars (default 76) banner.image.height= # Height of the banner image in chars (default based on image height) banner.image.margin= # Left hand image margin in chars (default 2) banner.image.invert= # If images should be inverted for dark terminal themes (default false) # LOGGING logging.config= # Location of the logging configuration file. For instance `classpath:logback.xml` for Logback logging.exception-conversion-word=%wEx # Conversion word used when logging exceptions. logging.file= # Log file name. For instance `myapp.log` logging.file.max-history= # Maximum of archive log files to keep. Only supported with the default logback setup. logging.file.max-size= # Maximum log file size. Only supported with the default logback setup. logging.level.*= # Log levels severity mapping. For instance `logging.level.org.springframework=DEBUG` logging.path= # Location of the log file. For instance `/var/log` logging.pattern.console= # Appender pattern for output to the console. Only supported with the default logback setup. logging.pattern.file= # Appender pattern for output to the file. Only supported with the default logback setup. logging.pattern.level= # Appender pattern for log level (default %5p). Only supported with the default logback setup. logging.pattern.dateformat= # Appender pattern for log dateformat (default yyyy-MM-dd HH:mm:ss.SSS). Only supported with the default logback setup. logging.register-shutdown-hook=false # Register a shutdown hook for the logging system when it is initialized. # AOP spring.aop.auto=true # Add @EnableAspectJAutoProxy. spring.aop.proxy-target-class=true # Whether subclass-based (CGLIB) proxies are to be created (true) as opposed to standard Java interface-based proxies (false). # IDENTITY (ContextIdApplicationContextInitializer) spring.application.index= # Application index. spring.application.name= # Application name. # ADMIN (SpringApplicationAdminJmxAutoConfiguration) spring.application.admin.enabled=false # Enable admin features for the application. spring.application.admin.jmx-name=org.springframework.boot:type=Admin,name=SpringApplication # JMX name of the application admin MBean. # AUTO-CONFIGURATION spring.autoconfigure.exclude= # Auto-configuration classes to exclude. # SPRING CORE spring.beaninfo.ignore=true # Skip search of BeanInfo classes. # SPRING CACHE (CacheProperties) spring.cache.cache-names= # Comma-separated list of cache names to create if supported by the underlying cache manager. spring.cache.caffeine.spec= # The spec to use to create caches. Check CaffeineSpec for more details on the spec format. spring.cache.couchbase.expiration=0ms # Entry expiration. By default the entries never expire. spring.cache.ehcache.config= # The location of the configuration file to use to initialize EhCache. spring.cache.infinispan.config= # The location of the configuration file to use to initialize Infinispan. spring.cache.jcache.config= # The location of the configuration file to use to initialize the cache manager. spring.cache.jcache.provider= # Fully qualified name of the CachingProvider implementation to use to retrieve the JSR-107 compliant cache manager. Only needed if more than one JSR-107 implementation is available on the classpath. spring.cache.redis.cache-null-values=true # Allow caching null values. spring.cache.redis.key-prefix= # Key prefix. spring.cache.redis.time-to-live=0ms # Entry expiration. By default the entries never expire. spring.cache.redis.use-key-prefix=true # Whether to use the key prefix when writing to Redis. spring.cache.type= # Cache type, auto-detected according to the environment by default. # SPRING CONFIG - using environment property only (ConfigFileApplicationListener) spring.config.location= # Config file locations. spring.config.name=application # Config file name. # HAZELCAST (HazelcastProperties) spring.hazelcast.config= # The location of the configuration file to use to initialize Hazelcast. # PROJECT INFORMATION (ProjectInfoProperties) spring.info.build.location=classpath:META-INF/build-info.properties # Location of the generated build-info.properties file. spring.info.git.location=classpath:git.properties # Location of the generated git.properties file. # JMX spring.jmx.default-domain= # JMX domain name. spring.jmx.enabled=true # Expose management beans to the JMX domain. spring.jmx.server=mbeanServer # MBeanServer bean name. # Email (MailProperties) spring.mail.default-encoding=UTF-8 # Default MimeMessage encoding. spring.mail.host= # SMTP server host. For instance `smtp.example.com` spring.mail.jndi-name= # Session JNDI name. When set, takes precedence to others mail settings. spring.mail.password= # Login password of the SMTP server. spring.mail.port= # SMTP server port. spring.mail.properties.*= # Additional JavaMail session properties. spring.mail.protocol=smtp # Protocol used by the SMTP server. spring.mail.test-connection=false # Test that the mail server is available on startup. spring.mail.username= # Login user of the SMTP server. # APPLICATION SETTINGS (SpringApplication) spring.main.banner-mode=console # Mode used to display the banner when the application runs. spring.main.sources= # Sources (class name, package name or XML resource location) to include in the ApplicationContext. spring.main.web-application-type= # Flag to explicitly request a specific type of web application. Auto-detected based on the classpath if not set. # FILE ENCODING (FileEncodingApplicationListener) spring.mandatory-file-encoding= # Expected character encoding the application must use. # INTERNATIONALIZATION (MessageSourceAutoConfiguration) spring.messages.always-use-message-format=false # Set whether to always apply the MessageFormat rules, parsing even messages without arguments. spring.messages.basename=messages # Comma-separated list of basenames, each following the ResourceBundle convention. spring.messages.cache-duration=-1 # Loaded resource bundle files cache duration. When not set, bundles are cached forever. spring.messages.encoding=UTF-8 # Message bundles encoding. spring.messages.fallback-to-system-locale=true # Set whether to fall back to the system Locale if no files for a specific Locale have been found. spring.messages.use-code-as-default-message=false # Set whether to use the message code as default message instead of throwing a "NoSuchMessageException". Recommended during development only. # OUTPUT spring.output.ansi.enabled=detect # Configure the ANSI output. # PID FILE (ApplicationPidFileWriter) spring.pid.fail-on-write-error= # Fail if ApplicationPidFileWriter is used but it cannot write the PID file. spring.pid.file= # Location of the PID file to write (if ApplicationPidFileWriter is used). # PROFILES spring.profiles.active= # Comma-separated list (or list if using YAML) of active profiles. spring.profiles.include= # Unconditionally activate the specified comma separated profiles (or list of profiles if using YAML). # QUARTZ SCHEDULER (QuartzProperties) spring.quartz.job-store-type=memory # Quartz job store type. spring.quartz.properties.*= # Additional Quartz Scheduler properties. spring.quartz.jdbc.initialize-schema=embedded # Database schema initialization mode. spring.quartz.jdbc.schema=classpath:org/quartz/impl/jdbcjobstore/tables_@@platform@@.sql # Path to the SQL file to use to initialize the database schema. # Reactor spring.reactor.stacktrace-mode.enabled=false # Set whether Reactor should collect stacktrace information at runtime. # SENDGRID (SendGridAutoConfiguration) spring.sendgrid.api-key= # SendGrid API key. spring.sendgrid.proxy.host= # SendGrid proxy host. spring.sendgrid.proxy.port= # SendGrid proxy port. # ---------------------------------------- # WEB PROPERTIES # ---------------------------------------- # EMBEDDED SERVER CONFIGURATION (ServerProperties) server.address= # Network address to which the server should bind to. server.compression.enabled=false # If response compression is enabled. server.compression.excluded-user-agents= # List of user-agents to exclude from compression. server.compression.mime-types=text/html,text/xml,text/plain,text/css,text/javascript,application/javascript # Comma-separated list of MIME types that should be compressed. server.compression.min-response-size=2048 # Minimum response size that is required for compression to be performed. server.connection-timeout= # Time that connectors will wait for another HTTP request before closing the connection. When not set, the connector's container-specific default will be used. Use a value of -1ms to indicate no (i.e. infinite) timeout. server.display-name=application # Display name of the application. server.max-http-header-size=0 # Maximum size in bytes of the HTTP message header. server.error.include-exception=false # Include the "exception" attribute. server.error.include-stacktrace=never # When to include a "stacktrace" attribute. server.error.path=/error # Path of the error controller. server.error.whitelabel.enabled=true # Enable the default error page displayed in browsers in case of a server error. server.http2.enabled=true # Whether to enable HTTP/2 support, if the current environment supports it. server.jetty.acceptors= # Number of acceptor threads to use. server.jetty.accesslog.append=false # Append to log. server.jetty.accesslog.date-format=dd/MMM/yyyy:HH:mm:ss Z # Timestamp format of the request log. server.jetty.accesslog.enabled=false # Enable access log. server.jetty.accesslog.extended-format=false # Enable extended NCSA format. server.jetty.accesslog.file-date-format= # Date format to place in log file name. server.jetty.accesslog.filename= # Log filename. If not specified, logs will be redirected to "System.err". server.jetty.accesslog.locale= # Locale of the request log. server.jetty.accesslog.log-cookies=false # Enable logging of the request cookies. server.jetty.accesslog.log-latency=false # Enable logging of request processing time. server.jetty.accesslog.log-server=false # Enable logging of the request hostname. server.jetty.accesslog.retention-period=31 # Number of days before rotated log files are deleted. server.jetty.accesslog.time-zone=GMT # Timezone of the request log.