SpringBoot項目新建遇到問題整理（一）

 

1.新建了一個SpringBoot項目：只引用需要用到的spring boot相關的jar包,除此之外沒有任何的配置

啟動application.java報錯：

APPLICATION FAILED TO START
***************************

Description:

Cannot determine embedded database driver class for database type NONE

Action:

If you want an embedded database please put a supported one on the classpath. If you have database settings to be loaded from a particular profile you may need to active it (no profiles are currently active).

--——————>原因：因為spring boot只要你在pom中引入了spring-boot-starter-data-jpa，他就會默認需要加載數據庫相關的配置

你要是沒有在配置文件中配置數據庫相關信息，它會加載默認的配置（不存在的） 然后就報錯了， 所以你要是要用數據庫相關的東西 你就完善配置
不用數據庫相關的東西 就不要在pom中引入相關依賴。

--------------------->解決:注釋掉引用的數據庫相關的jar，即可正常啟動

 

2.新建一個小項目，springboot使用1.5.16，項目啟動類使用注解@SpringBootApplication，controller使用注解@Controller,瀏覽器輸入ip地址報錯：

Whitelabel Error Page

This application has no explicit mapping for /error, so you are seeing this as a fallback.

Tue Jan 08 13:48:08 CST 2019

There was an unexpected error (type=Not Found, status=404).

No message available

原因： 控制器的URL路徑沒有找到

 

@controller改成@RestController頁面可正常顯示

3.pom.xml中配置了熱啟動，但是修改controller后沒有重新加載，console控制台也沒有加載新的內容-》熱啟動沒有生效

查找原因：熱部署依賴於項目的自動編譯功能：Project->Build Automatically（自動編譯）是否已經勾選，若沒勾選，則需要勾選，否則熱啟動無用

4.SpringBoot項目啟動類*Application.java：SpringBoot項目只能有一個main方法：

其中：@SpringBootApplication     等價於

@Controller
@EnableAutoConfiguration
@ComponentScan("com.yst.helloWOrld.web")

 5.Junit單元測試使用MockMvc做controller接口測試

（51）直接返回字符串中含有中文---》中文亂碼

JunitTest代碼為：

package com.yst.helloWorld;

import org.junit.Before;
import org.junit.Test;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.web.servlet.MockMvc;
import org.springframework.test.web.servlet.MvcResult;
import org.springframework.test.web.servlet.ResultHandler;
import org.springframework.test.web.servlet.request.MockMvcRequestBuilders;
import org.springframework.test.web.servlet.setup.MockMvcBuilders;
import com.yst.helloWorld.web.HelloWorldController;

@SpringBootTest
public class HelloWorldApplicationTests {
    //使用MockMvc做controller接口測試
    private MockMvc mockMvc;
    
    @Before //這個方法在每個方法執行之前都會執行一遍
    public void setUp() throws Exception {
        mockMvc = MockMvcBuilders.standaloneSetup(new HelloWorldController()).build();
    }
    @Test
    public void getHello() throws Exception  {
        mockMvc.perform(MockMvcRequestBuilders.post("/hello")//請求的url,請求的方法是post
//                .contentType(MediaType.APPLICATION_FORM_URLENCODED)
//                .param("name", "value")//添加參數
        ).andDo(new ResultHandler() {
            @Override
            public void handle(MvcResult result) throws Exception {
                result.getResponse().setCharacterEncoding("UTF-8");
                System.out.println("結果："+result.getResponse().getContentAsString());//result.getResponse().getContentAsString()不支持中文格式
                System.out.println("請求狀態碼："+result.getResponse().getStatus());//result.getResponse().getContentAsString()不支持中文格式
            }
        });
    }
    
//    @Test
//    public void hello() {
//        System.out.println("hello");
//    }
//    @Test
//    public void contextLoads() {
//    }

}

controller代碼：

package com.yst.helloWorld.web;

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
@RestController
//@Controller
public class HelloWorldController {
    
    @RequestMapping(value="/hello")
    public String hello() {
        return "hello my world! 我的世界";                
    }
    
    @RequestMapping(value="/findUser/{userId}")  
    public String findUser(@PathVariable String userId, Model model) {  
      return "my User:"+userId;   
    }  
    
    @RequestMapping(value="/{textualPart:[a-z-]+}.{numericPart:[\\d]+}")  
    public String regularExpression(  
      @PathVariable String textualPart,  
      @PathVariable String numericPart){  
      
        System.out.println("Textual part: " + textualPart +   
          ", numeric part: " + numericPart);  
        return "someResult";  
    }
    
      @RequestMapping(value = "/pets/{petId}", method = RequestMethod.GET, params="myParam=myValue")  
      public void findPet(@PathVariable String ownerId, @PathVariable String petId, Model model) {      
        // implementation omitted  
      }  

    
}

執行結果為：

結果：hello my world! ????     ----------》中文顯示正常
請求狀態碼：200

---》解決方式：暫時未解決

（52）返回對象或集合：對象字段含有中文--》返回結果正常顯示

controller代碼：

package com.yst.helloWorld.web;

import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

import com.yst.helloWorld.domain.User;
@RestController
public class HelloWorldController {
    
    @RequestMapping("/getUser")
    public User getUser() {
        User user = new User();
        user.setName("王火火");
        user.setAge(18);
        user.setPass("123456");
        return user;
        
    }
　　　　
}

JunitTest代碼：

package com.yst.helloWorld;

import org.junit.Before;
import org.junit.Test;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.web.servlet.MockMvc;
import org.springframework.test.web.servlet.MvcResult;
import org.springframework.test.web.servlet.ResultHandler;
import org.springframework.test.web.servlet.request.MockMvcRequestBuilders;
import org.springframework.test.web.servlet.setup.MockMvcBuilders;
import com.yst.helloWorld.web.HelloWorldController;

@SpringBootTest
public class HelloWorldApplicationTests {
    //使用MockMvc做controller接口測試
    private MockMvc mockMvc;
    
    @Before //這個方法在每個方法執行之前都會執行一遍
    public void setUp() throws Exception {
        mockMvc = MockMvcBuilders.standaloneSetup(new HelloWorldController()).build();
    }
    
    @Test
    public void getUser() throws Exception  {
        mockMvc.perform(MockMvcRequestBuilders.post("/getUser"))//請求的url,請求的方法是post
        .andDo(new ResultHandler() {
            @Override
            public void handle(MvcResult result) throws Exception {
//                result.getResponse().setCharacterEncoding("UTF-8");
                System.out.println("結果："+result.getResponse().getContentAsString());//
                System.out.println("請求狀態碼："+result.getResponse().getStatus());//
            }
        });
    }
    


}

結果為：

結果：{"name":"王火火","age":18,"pass":"123456"}      ------》說明SpringBoot自動將對象轉換為Json進行返回
請求狀態碼：200

若返回集合，代碼如下：

@RequestMapping("/getUsers")
    public List<User> getUsers() {
        List<User> users = new ArrayList<User>();
        User u1 = new User();
        u1.setName("王火火");
        u1.setAge(18);
        u1.setPass("123456");
        users.add(u1);
        User u2 = new User();
        u2.setName("張明");
        u2.setAge(18);
        u2.setPass("123");
        users.add(u2);
        return users;
        
}

添加測試方法進行測試，返回內容為：

結果：[{"name":"王火火","age":18,"pass":"123456"},{"name":"張明","age":18,"pass":"123"}]
請求狀態碼：200

so，這說明不管對象/集合/嵌套對象，SpringBoot均可以將其轉換為Json字符串，Spring天然對Json支持；

特別適用於給其他系統提供接口。

 6.查看SpringBoot匹配的環境版本：

Spring官網：https://spring.io/--->projects--->Spring boot--->Learn--->選取一個版本，點擊Reference Doc. --->往下拉：查看：

9.System Requirements 和 9.1 Servlet Containers

如圖：

 

7.限制請求方式：@RequestMapping(method=RequestMethod.POST)

@RequestMapping(name = "/getUser",method=RequestMethod.POST)//為安全，只允許post請求訪問
    public User getUser() {
        User user = new User();
        user.setName("王火火");
        user.setAge(18);
        user.setPass("123456");
        return user;
}

若以get方式請求，會返回：org.springframework.web.HttpRequestMethodNotSupportedException: Request method 'GET' not supported]

 8.傳參方式

（1）使用對象接收:適用於從頁面獲取值：頁面中只要是屬於User的屬性都會被自動填充到該對象中

@RequestMapping(name = "/getUser",method=RequestMethod.POST)//
public User getUser(User user) {
    return user;
}

(2)適用url進行傳參：@PathVariable（import org.springframework.web.bind.annotation.PathVariable;）

(

注意兩個區別

• @PathVariable是獲取url上數據的。
• @RequestParam獲取請求參數的（包括post表單提交）

)

//注意url模板中的占位符的值必須和@PathVariable中的值相同才能完成綁定
    @RequestMapping(name = "/getUser/{useName}",method=RequestMethod.GET)//
    public User getUser(@PathVariable  String useName) {
        User user = new User();  
        user.setName(useName);
        user.setAge(18);
        return user;
}

然后在瀏覽器輸入地址：http://localhost:8080/getUser/whh  ,結果竟然報錯：

報錯：

Whitelabel Error Page

This application has no explicit mapping for /error, so you are seeing this as a fallback.

Thu Jan 17 10:27:27 CST 2019

There was an unexpected error (type=Internal Server Error, status=500).

Missing URI template variable 'useName' for method parameter of type String

------>網上搜了很多資料，一般這種報錯都是因為：controller上的@RequestMapping的實參和方法里面的形參名字不一致，但是我的代碼兩個參數“userName”是一樣的

然后我又試了適用別名的方法，還是不行：代碼如下：

@RequestMapping(name = "/getUser/{userN}",method=RequestMethod.GET)//
    public User getUser(@PathVariable("userN") @Valid  String useName) {
        User user = new User();  
        user.setName(useName);
        user.setAge(18);
        return user;
}

---->最后終於找到了原因：竟是因為RequestMapping的參數問題:不小心把value寫成了name。   改成value后，瀏覽器頁面返回：

{"name":"whh","age":18,"pass":null}

查看下面源碼可知：name:Assign a name to this mapping.(給這個mapping分配一個名稱)，沒有實質性的作用;

類似於注釋，對程序沒什么影響，但是對人友好，因為有些url是拼音的，隔了幾個月沒有注釋的話可能不知道這個url干嗎的

所以，RequestMapping地址進行映射：只能用value或path,不能使用name.

@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Mapping
public @interface RequestMapping {

    /**
     * Assign a name to this mapping.
     * <p><b>Supported at the type level as well as at the method level!</b>
     * When used on both levels, a combined name is derived by concatenation
     * with "#" as separator.
     * @see org.springframework.web.servlet.mvc.method.annotation.MvcUriComponentsBuilder
     * @see org.springframework.web.servlet.handler.HandlerMethodMappingNamingStrategy
     */
    String name() default "";

    /**
     * The primary mapping expressed by this annotation.
     * <p>In a Servlet environment this is an alias for {@link #path}.
     * For example {@code @RequestMapping("/foo")} is equivalent to
     * {@code @RequestMapping(path="/foo")}.
     * <p>In a Portlet environment this is the mapped portlet modes
     * (i.e. "EDIT", "VIEW", "HELP" or any custom modes).
     * <p><b>Supported at the type level as well as at the method level!</b>
     * When used at the type level, all method-level mappings inherit
     * this primary mapping, narrowing it for a specific handler method.
     */
    @AliasFor("path")
    String[] value() default {};

    /**
     * In a Servlet environment only: the path mapping URIs (e.g. "/myPath.do").
     * Ant-style path patterns are also supported (e.g. "/myPath/*.do").
     * At the method level, relative paths (e.g. "edit.do") are supported
     * within the primary mapping expressed at the type level.
     * Path mapping URIs may contain placeholders (e.g. "/${connect}").
     * <p><b>Supported at the type level as well as at the method level!</b>
     * When used at the type level, all method-level mappings inherit
     * this primary mapping, narrowing it for a specific handler method.
     * @see org.springframework.web.bind.annotation.ValueConstants#DEFAULT_NONE
     * @since 4.2
     */
    @AliasFor("value")
    String[] path() default {};

    /**
     * The HTTP request methods to map to, narrowing the primary mapping:
     * GET, POST, HEAD, OPTIONS, PUT, PATCH, DELETE, TRACE.
     * <p><b>Supported at the type level as well as at the method level!</b>
     * When used at the type level, all method-level mappings inherit
     * this HTTP method restriction (i.e. the type-level restriction
     * gets checked before the handler method is even resolved).
     * <p>Supported for Servlet environments as well as Portlet 2.0 environments.
     */
    RequestMethod[] method() default {};

    

}

 9.參數校驗依賴於hibernate-validator：見下圖

SpringBoot使用:@Valid（package javax.validation;屬於validation-api-1.1.0.Final.jar）+BindingResult進行參數校驗：代碼如下:

User類：

package com.yst.helloWorld.domain;

import javax.validation.constraints.Max;
import javax.validation.constraints.Min;

import org.hibernate.validator.constraints.Length;
import org.hibernate.validator.constraints.NotEmpty;

public class User {
    @NotEmpty(message="姓名不能為空")
    private String name;
    @Max(value=100,message="年齡不能大於 100 歲")
    @Min(value=18,message="必須年滿 18 歲")
    private int age;
    @NotEmpty(message="密碼不能為空|")
    @Length(min=6,message="密碼長度不能小於6位")
    private String pass;
    //...
    

}

controller方法：

/**
     * 參數校驗@Valid+BindingResult
     * 打印錯誤信息
     * @param user
     * @param result
     */
    @RequestMapping("/saveUser")
    public void saveUser(@Valid User user,BindingResult result) {
        System.out.println("user:"+user);
        if(result.hasErrors()) {
            List<ObjectError> list = result.getAllErrors();
            for (ObjectError error : list) {
                System.out.println(error.getCode()+"-"+error.getDefaultMessage());
            }
        }
    }

測試方法：

@Test
    public void saveUser() throws Exception  {
        mockMvc.perform(MockMvcRequestBuilders.post("/saveUser")//請求的url,請求的方法是post
                .param("name", "")//添加參數
                .param("age", "222")//添加參數
                .param("pass", "123")//添加參數
        ).andDo(new ResultHandler() {
            @Override
            public void handle(MvcResult result) throws Exception {
                System.out.println("結果："+result.getResponse().getContentAsString());
                System.out.println("請求狀態碼："+result.getResponse().getStatus());
            }
        });
    }

 

結果返回：

user:com.yst.helloWorld.domain.User@119cbf96
Max-年齡不能大於 100 歲
NotEmpty-姓名不能為空
Length-密碼長度不能小於6位

 結果顯示已經觸發了校驗規則，返回了錯誤信息。實際項目開發中可以對錯誤信息進行包裝，返回前端頁面展示。

10.自定義資源文件Property:代碼如下

application.properties：

#application.properties
com.whh.title=whh
com.whh.description=分享技術和生活

自定義配置類：

package com.yst.helloWorld.domain;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
@Component
public class WhhProperties {
    @Value("${com.whh.title}")
    private String title;
    @Value("${com.whh.description}")
    private String description;
    public String getTitle() {
        return title;
    }
    public void setTitle(String title) {
        this.title = title;
    }
    public String getDescription() {
        return description;
    }
    public void setDescription(String description) {
        this.description = description;
    }
    
    

}

單元測試代碼：

package com.yst.helloWorld;

import javax.annotation.Resource;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.test.context.junit4.SpringRunner;
import com.yst.helloWorld.domain.WhhProperties;
//@RunWith:運行器，讓測試運行於Spring環境;
//@RunWith(SpringRunner.class)=@RunWith(SpringJUnit4ClassRunnerRunner.class);SpringRunner extends SpringJUnit4ClassRunner 
@RunWith(SpringRunner.class)
@SpringBootTest
public class PropertiesTest {
    @Resource
    private WhhProperties whhProperties;
    
    @Test
    public void testProperties() throws Exception {
        System.out.println("title:"+whhProperties.getTitle());
        System.out.println("description:"+whhProperties.getDescription());
    }

}

運行結果：

title:whh
description:分享技术和生活

------》出現中文亂碼，暫時未解決

 11.Spring Data Jpa數據庫連接：

（1）添加依賴：

 

　　　　　<!--jpa的jar包 ，操作數據庫的，類似hibernate-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency> 
        <!-- 由於Oracle授權問題，Maven不提供Oracle JDBC driver，
         為了在Maven項目中應用Oracle JDBC driver,必須手動添加到本地倉庫。 -->
　　　　<!-- oracle數據庫驅動 -->
  　　<dependency>
            <groupId>com.oracle</groupId>
            <artifactId>ojdbc6</artifactId>
            <version>11.2.0.1.0</version>
 　　 </dependency>

 

由於Oracle授權問題，Maven不提供Oracle JDBC driver，所以maven的中央倉庫中沒有這個資源（所以會報錯：Missing artifact com.oracle:ojdbc6:jar:11.2.0.1.0，如下圖），

為了在Maven項目中應用Oracle JDBC driver,必須手動添加到本地倉庫

 

 （2）將ojdbc6.jar添加到本地倉庫：

首先，oracle版本11.2.0，需要在--app\product\11.2.0\dbhome_1\jdbc\lib路徑下找到ojdbc6.jar,也可以到官網下載。

然后將

然后將ojdbc6.jar 放在某目錄:然后cmd--命令行：在該目錄下輸入：

mvn install:install-file -DgroupId=com.oracle -DartifactId=ojdbc6 -Dversion=11.2.0.1.0 -Dpackaging=jar -Dfile=ojdbc6.jar

執行成功。

然后右擊項目-》maven-》update Project-》OK

更新項目后pom.xml就不會報錯了

（3）添加配置文件

新建properties文件：點擊：src/main/resources目錄---》點擊File菜單---》new ---》FIle--》FIle name:datasource.properties---》finish。完成資源文件的創建

 

 

 

 

 （4）備注整理在springboot的application.properties中，配置各種數據庫的方法：

轉載自：http://blog.chinaunix.net/uid-24648266-id-5758602.html

mysql

spring.jpa.database=MYSQL
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL5Dialect
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.url=jdbc:mysql://127.0.0.1:3306/mydbname?useSSL=false
spring.datasource.username=user1
spring.datasource.password=user1

 <dependency>
     <groupId>mysql</groupId>
     <artifactId>mysql-connector-java</artifactId>
     <version>5.1.34</version>
 </dependency>

oracle

 spring.jpa.database = oracle
 spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.Oracle10gDialect
 spring.datasource.driverClassName=oracle.jdbc.driver.OracleDriver
 spring.datasource.url=jdbc:oracle:thin:@127.0.0.1:1521:xe
 spring.datasource.username=user1
 spring.datasource.password=user1

 <dependency>
     <groupId>com.oracle</groupId>
     <artifactId>ojdbc7</artifactId>
     <version>12.1.0.2.0</version>
 </dependency>

sqlserver

 spring.jpa.database = sql_server
 spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.SQLServerDialect
 spring.datasource.driverClassName=com.microsoft.sqlserver.jdbc.SQLServerDriver
 spring.datasource.url=jdbc:sqlserver://127.0.0.1:1433;databaseName=mydbname
 spring.datasource.username=user1
 spring.datasource.password=user1

 <dependency>
     <groupId>com.microsoft.sqlserver</groupId>
     <artifactId>mssql-jdbc</artifactId>
     <version>6.1.0.jre8</version>
 </dependency>

（5）啟動項目報錯：Cannot determine embedded database driver class for database type NONE

 （51）問題分析：

If you want an embedded database please put a supported one on the classpath. If you have database settings to be loaded from a particular profile you may need to active it (no profiles are currently active).

這是因為spring boot默認會加載org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration類，DataSourceAutoConfiguration類使用了@Configuration注解向spring注入了dataSource bean。因為工程中沒有關於dataSource相關的配置信息，當spring創建dataSource bean因缺少相關的信息就會報錯。所以阻止spring boot自動注入dataSource bean

因為我僅僅只是使用spring boot來寫一些很簡單的例子來學習它，在Application類上增加@EnableAutoConfiguration(exclude={DataSourceAutoConfiguration.class})

代碼如下：

package com.yst.helloWorld;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration;
import org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.stereotype.Controller;

@SpringBootApplication    
//@Controller
//@EnableAutoConfiguration
//@ComponentScan("com.yst.helloWOrld.web")
15 @EnableAutoConfiguration(exclude={DataSourceAutoConfiguration.class})
public class HelloWorldApplication {

    public static void main(String[] args) {
         //啟動Spring Boot項目的唯一入口  
        SpringApplication.run(HelloWorldApplication.class, args);
    }
}

但是重新啟動還是報錯：錯誤如下：

 

原因：@SpringBootApplication = (默認屬性)@Configuration + @EnableAutoConfiguration + @ComponentScan。springboot會自動注入數據源，而你卻沒有配，所以他就拋出該異常。

這說明剛才的@SpringBootApplication(exclude={DataSourceAutoConfiguration.class})並沒有起到不注入數據源的作用，是哪里出錯了嗎？

查資料好像應該是配置這個：@SpringBootApplication(exclude={DataSourceAutoConfiguration.class,HibernateJpaAutoConfiguration.class})

代碼如下

package com.yst.helloWorld;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration;
import org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.stereotype.Controller;

@SpringBootApplication    
//@Controller
//@EnableAutoConfiguration
//@ComponentScan("com.yst.helloWOrld.web")
@EnableAutoConfiguration(exclude={DataSourceAutoConfiguration.class,HibernateJpaAutoConfiguration.class}) 16 public class HelloWorldApplication {

    public static void main(String[] args) {
         //啟動Spring Boot項目的唯一入口  
        SpringApplication.run(HelloWorldApplication.class, args);
    }
}

啟動，報錯：

org.apache.catalina.LifecycleException: Failed to start component [Connector[HTTP/1.1-8080]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:167) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.apache.catalina.core.StandardService.addConnector(StandardService.java:225) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainer.addPreviouslyRemovedConnectors(TomcatEmbeddedServletContainer.java:265) [spring-boot-1.5.16.RELEASE.jar:1.5.16.RELEASE]
    at org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainer.start(TomcatEmbeddedServletContainer.java:208) [spring-boot-1.5.16.RELEASE.jar:1.5.16.RELEASE]
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.startEmbeddedServletContainer(EmbeddedWebApplicationContext.java:297) [spring-boot-1.5.16.RELEASE.jar:1.5.16.RELEASE]
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.finishRefresh(EmbeddedWebApplicationContext.java:145) [spring-boot-1.5.16.RELEASE.jar:1.5.16.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:546) [spring-context-4.3.19.RELEASE.jar:4.3.19.RELEASE]
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:122) [spring-boot-1.5.16.RELEASE.jar:1.5.16.RELEASE]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:693) [spring-boot-1.5.16.RELEASE.jar:1.5.16.RELEASE]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:360) [spring-boot-1.5.16.RELEASE.jar:1.5.16.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:303) [spring-boot-1.5.16.RELEASE.jar:1.5.16.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1118) [spring-boot-1.5.16.RELEASE.jar:1.5.16.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1107) [spring-boot-1.5.16.RELEASE.jar:1.5.16.RELEASE]
    at com.yst.helloWorld.HelloWorldApplication.main(HelloWorldApplication.java:20) [classes/:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_181]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_181]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_181]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_181]
    at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49) [spring-boot-devtools-1.5.16.RELEASE.jar:1.5.16.RELEASE]
Caused by: org.apache.catalina.LifecycleException: Protocol handler start failed
    at org.apache.catalina.connector.Connector.startInternal(Connector.java:1020) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
    ... 18 common frames omitted
Caused by: java.net.BindException: Address already in use: bind
    at sun.nio.ch.Net.bind0(Native Method) ~[na:1.8.0_181]
    at sun.nio.ch.Net.bind(Net.java:433) ~[na:1.8.0_181]
    at sun.nio.ch.Net.bind(Net.java:425) ~[na:1.8.0_181]
    at sun.nio.ch.ServerSocketChannelImpl.bind(ServerSocketChannelImpl.java:223) ~[na:1.8.0_181]
    at sun.nio.ch.ServerSocketAdaptor.bind(ServerSocketAdaptor.java:74) ~[na:1.8.0_181]
    at org.apache.tomcat.util.net.NioEndpoint.bind(NioEndpoint.java:219) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.apache.tomcat.util.net.AbstractEndpoint.start(AbstractEndpoint.java:1151) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.apache.coyote.AbstractProtocol.start(AbstractProtocol.java:591) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.apache.catalina.connector.Connector.startInternal(Connector.java:1018) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
    ... 19 common frames omitted

2019-02-25 18:38:49.873  INFO 9852 --- [  restartedMain] o.apache.catalina.core.StandardService   : Stopping service [Tomcat]
2019-02-25 18:38:49.973  INFO 9852 --- [  restartedMain] utoConfigurationReportLoggingInitializer : 

Error starting ApplicationContext. To display the auto-configuration report re-run your application with 'debug' enabled.
2019-02-25 18:38:50.009 ERROR 9852 --- [  restartedMain] o.s.b.d.LoggingFailureAnalysisReporter   : 

***************************
APPLICATION FAILED TO START
***************************

Description:

The Tomcat connector configured to listen on port 8080 failed to start. The port may already be in use or the connector may be misconfigured.

Action:

Verify the connector's configuration, identify and stop any process that's listening on port 8080, or configure this application to listen on another port.

 原來是8080端口被占用：

解決步驟：打開cmd命令窗口  輸入指令：netstat -ano 查看所有端口和PID，如下圖所示：

 

　　

然后找到對應的端口對應的PID  輸入指令： tasklist | findstr "15132"   找到對應的進程；輸入 命令：taskkill /f /t /im javaw.exe   殺掉該進程就可以啦(殺進程也可以使用kill命令：kill xxx，常用：：kill －9 pid)

重新啟動，啟動成功:如圖：