笔记：Spring Cloud Eureka 服务发现与消费

服务发现与消费，其服务发现的任务是由Eureka的客户端完成，而服务的消费任务由Ribbon、JerseyClient等完成，Ribbon是一个基于HTTP和TCP的客户端负载均衡器；使用JerseyClient是一个基于HTTP的客户端调用组件，需要需要增加负载均衡器，需要自己来实现，示例代码如下：

• 创建一个Spring
  Boot
  的基础工程来实现服务消费者，并在pom.xml
  中引入必须依赖项
  spring-cloud-starter-eureka，引入
  spring-cloud-starter-web
  来实现Spring
  MVC
  的REST服务进行测试

  <?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>

• 创建应用主类
  ConsumerHelloserviceApplication ，通过 @EanbleDiscoveryClient
  注解将应用注册为Eureka
  客户端应用，以获取服务发现的能力，代码如下：

  @EnableDiscoveryClient

  @SpringBootApplication

  public class ConsumerHelloserviceApplication {

  public static
  void
  main(String[] args) {

  SpringApplication.run(ConsumerHelloserviceApplication.class, args);

  }

  }

• 创建 ConsumerController 类，并实现 /consumer 接口，在接口中对服务的调用，这里使用的是服务的名而不是一个具体的地址，服务消费Java代码：

  @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
  服务注册中心的位置，需要和服务提供者的一致，否则是无法发现服务的，同时设置该消费者的端口号，代码如下：

  server.port=8090

  spring.application.name=consumer-helloservice

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

• 启动consumer-helloservice应用后，我们可以在Eureka信息面板中看到，我们实现的 CONSUMER-HELLOSERVICE 服务，访问地址
  http://localhost:8090/consumer 可以看到请求返回内容：

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