Spring Cloud Eureka 服務發現與消費

服務發現與消費，其服務發現的任務是由Eureka的客戶端完成，而服務的消費任務由Ribbon、JerseyClient等完成，Ribbon是一個基於HTTP和TCP的客戶端負載均衡器；使用JerseyClient是一個基於HTTP的客戶端調用組件，需要需要增加負載均衡器，需要自己來實現，示例代碼如下：

• 創建一個Spring Boot 的基礎工程來實現服務消費者，並在pom.xml 中引入必須依賴項 spring-cloud-starter-eureka，引入 spring-cloud-starter-web 來實現Spring MVC 的REST服務進行測試

  <?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>org.drsoft.consumer</groupId>

          <artifactId>consumer-helloservice</artifactId>

          <version>0.0.1-SNAPSHOT</version>

          <packaging>jar</packaging>

          <name>consumer-helloservice</name>

          <description>Demo project for Spring Boot</description>

          <parent>

                  <groupId>org.springframework.boot</groupId>

                  <artifactId>spring-boot-starter-parent</artifactId>

                  <version>1.5.6.RELEASE</version>

                  <relativePath/> <!-- lookup parent from repository -->

          </parent>

          <properties>

                  <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

                  <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>

                  <java.version>1.8</java.version>

                  <spring-cloud.version>Dalston.SR2</spring-cloud.version>

          </properties>

          <dependencies>

                  <dependency>

                          <groupId>org.springframework.cloud</groupId>

                          <artifactId>spring-cloud-starter-eureka</artifactId>

                  </dependency>

                  <dependency>

                          <groupId>org.springframework.boot</groupId>

                          <artifactId>spring-boot-starter-web</artifactId>

                  </dependency>

                  <dependency>

                          <groupId>org.springframework.boot</groupId>

                          <artifactId>spring-boot-starter-test</artifactId>

                          <scope>test</scope>

                  </dependency>

          </dependencies>

          <dependencyManagement>

                  <dependencies>

                          <dependency>

                                  <groupId>org.springframework.cloud</groupId>

                                  <artifactId>spring-cloud-dependencies</artifactId>

                                  <version>${spring-cloud.version}</version>

                                  <type>pom</type>

                                  <scope>import</scope>

                          </dependency>

                  </dependencies>

          </dependencyManagement>

          <build>

                  <plugins>

                          <plugin>

                                  <groupId>org.springframework.boot</groupId>

                                  <artifactId>spring-boot-maven-plugin</artifactId>

                          </plugin>

                  </plugins>

          </build>

  </project>

• 創建應用主類 ConsumerHelloserviceApplication ，通過 @EanbleDiscoveryClient 注解將應用注冊為Eureka 客戶端應用，以獲取服務發現的能力，代碼如下：

  @EnableDiscoveryClient

  @SpringBootApplication

  public class ConsumerHelloserviceApplication {

     

          public static void main(String[] args) {

                  SpringApplication.run(ConsumerHelloserviceApplication.class, args);

          }

  }

• 創建 ConsumerController 類，並實現 /consumer 接口，在接口中對服務的調用，這里使用的是服務的名而不是一個具體的地址，服務消費Java代碼：

  @RestController

  public class ConsumerController {

          @Autowired

          private DiscoveryClient discoveryClient;

     

          @RequestMapping (value = "/consumer", method = RequestMethod.GET)

          public String helloConsumer() {

                  List<ServiceInstance> serviceInstanceList = discoveryClient.getInstances("org.drsoft.webservice.helloservice");

                  StringBuilder stringBuilder = new StringBuilder();

                  URI uri = null;

                  for (ServiceInstance instance : serviceInstanceList) {

                          stringBuilder.append("host=" + instance.getHost());

                          stringBuilder.append("port=" + instance.getPort());

                          stringBuilder.append("serviceId=" + instance.getServiceId());

                          stringBuilder.append("uri=" + instance.getUri());

                          stringBuilder.append("\n");

     

                          uri = instance.getUri();

                  }

     

                  String uriString = uri.toString() + "/hello/get";

                  stringBuilder.append("response body=" + new RestTemplate().getForEntity(uriString, String.class).getBody());

                  return stringBuilder.toString();

          }

  }

• 在 application.properties 中配置Eureka 服務注冊中心的位置，需要和服務提供者的一致，否則是無法發現服務的，同時設置該消費者的端口號，代碼如下：

  server.port=8090

  spring.application.name=consumer-helloservice

     

  eureka.client.service-url.defaultZone=http://eurekaserver1:1111/eureka/,http://eurekaserver2:1112/eureka

• 啟動consumer-helloservice應用后，我們可以在Eureka信息面板中看到，我們實現的 CONSUMER-HELLOSERVICE 服務，訪問地址 http://localhost:8090/consumer 可以看到請求返回內容：

  host=192.168.196.187port=8085serviceId=ORG.DRSOFT.WEBSERVICE.HELLOSERVICEuri=http://192.168.196.187:8085 response body=get ok