修改Controller。

package com.itmuch.cloud.study.user.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.discovery.DiscoveryClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

import com.itmuch.cloud.study.user.entity.User;

import java.util.List;

@RestController
public class MovieController {
  @Autowired
  private RestTemplate restTemplate;

  @Autowired
  private DiscoveryClient discoveryClient;

  @GetMapping("/user/{id}")
  public User findById(@PathVariable Long id) {
    return this.restTemplate.getForObject("http://localhost:8000/" + id, User.class);
  }

  /**
   * 查询microservice-provider-user服务的信息并返回
   * @return microservice-provider-user服务的信息
   */
  @GetMapping("/user-instance")
  public List<ServiceInstance> showInfo(){
    return this.discoveryClient.getInstances("microservice-provider-user");
  }
}

使用DiscoveryClient.getInstances(serviceId)，可查询指定微服务在Eureka上的实例列表。

测试

1. 启动microservice-discovery-eureka——服务注册组件。

2. 启动microserver-provider-user-my-metadata——服务提供者。

3. 启动microservice-consumer-movie-understanding-metadata——服务消费者。

4. 访问http://localhost:8761/eureka/apps可查看Eureka的metadata。

   This XML file does not appear to have any style information associated with it. The document tree is shown below.
   <?xml version="1.0" encoding="utf-8"?>
   
   <applications> 
     <versions__delta>1</versions__delta>  
     <apps__hashcode>UP_2_</apps__hashcode>  
     <application> 
       <name>MICROSERVICE-CONSUMER-MOVIE</name>  
       <instance> 
         <instanceId>YPThinkPad:microservice-consumer-movie:8010</instanceId>  
         <hostName>192.168.31.58</hostName>  
         <app>MICROSERVICE-CONSUMER-MOVIE</app>  
         <ipAddr>192.168.31.58</ipAddr>  
         <status>UP</status>  
         <overriddenstatus>UNKNOWN</overriddenstatus>  
         <port enabled="true">8010</port>  
         <securePort enabled="false">443</securePort>  
         <countryId>1</countryId>  
         <dataCenterInfo class="com.netflix.appinfo.InstanceInfo$DefaultDataCenterInfo"> 
           <name>MyOwn</name> 
         </dataCenterInfo>  
         <leaseInfo> 
           <renewalIntervalInSecs>30</renewalIntervalInSecs>  
           <durationInSecs>90</durationInSecs>  
           <registrationTimestamp>1563686373426</registrationTimestamp>  
           <lastRenewalTimestamp>1563693725912</lastRenewalTimestamp>  
           <evictionTimestamp>0</evictionTimestamp>  
           <serviceUpTimestamp>1563685966027</serviceUpTimestamp> 
         </leaseInfo>  
         <metadata class="java.util.Collections$EmptyMap"/>  
         <homePageUrl>http://192.168.31.58:8010/</homePageUrl>  
         <statusPageUrl>http://192.168.31.58:8010/info</statusPageUrl>  
         <healthCheckUrl>http://192.168.31.58:8010/health</healthCheckUrl>  
         <vipAddress>microservice-consumer-movie</vipAddress>  
         <secureVipAddress>microservice-consumer-movie</secureVipAddress>  
         <isCoordinatingDiscoveryServer>false</isCoordinatingDiscoveryServer>  
         <lastUpdatedTimestamp>1563686373426</lastUpdatedTimestamp>  
         <lastDirtyTimestamp>1563686372796</lastDirtyTimestamp>  
         <actionType>ADDED</actionType> 
       </instance> 
     </application>  
     <application> 
       <name>MICROSERVICE-PROVIDER-USER</name>  
       <instance> 
         <instanceId>YPThinkPad:microservice-provider-user:8000</instanceId>  
         <hostName>192.168.31.58</hostName>  
         <app>MICROSERVICE-PROVIDER-USER</app>  
         <ipAddr>192.168.31.58</ipAddr>  
         <status>UP</status>  
         <overriddenstatus>UNKNOWN</overriddenstatus>  
         <port enabled="true">8000</port>  
         <securePort enabled="false">443</securePort>  
         <countryId>1</countryId>  
         <dataCenterInfo class="com.netflix.appinfo.InstanceInfo$DefaultDataCenterInfo"> 
           <name>MyOwn</name> 
         </dataCenterInfo>  
         <leaseInfo> 
           <renewalIntervalInSecs>30</renewalIntervalInSecs>  
           <durationInSecs>90</durationInSecs>  
           <registrationTimestamp>1563685921736</registrationTimestamp>  
           <lastRenewalTimestamp>1563693723982</lastRenewalTimestamp>  
           <evictionTimestamp>0</evictionTimestamp>  
           <serviceUpTimestamp>1563685921035</serviceUpTimestamp> 
         </leaseInfo>  
         <metadata> 
           <my-metadata>我自定义的元数据</my-metadata> 
         </metadata>  
         <homePageUrl>http://192.168.31.58:8000/</homePageUrl>  
         <statusPageUrl>http://192.168.31.58:8000/info</statusPageUrl>  
         <healthCheckUrl>http://192.168.31.58:8000/health</healthCheckUrl>  
         <vipAddress>microservice-provider-user</vipAddress>  
         <secureVipAddress>microservice-provider-user</secureVipAddress>  
         <isCoordinatingDiscoveryServer>false</isCoordinatingDiscoveryServer>  
         <lastUpdatedTimestamp>1563685921736</lastUpdatedTimestamp>  
         <lastDirtyTimestamp>1563685920502</lastDirtyTimestamp>  
         <actionType>ADDED</actionType> 
       </instance> 
     </application> 
   </applications>
   

5. 访问http://localhost:8010/user-instance，可以返回类似如下的内容。

   [{
   	host: "192.168.31.58",
   	port: 8000,
   	metadata: {
   		my - metadata: "我自定义的元数据"
   	},
   	secure: false,
   	uri: "http://192.168.31.58:8000",
   	instanceInfo: {
   		instanceId: "YPThinkPad:microservice-provider-user:8000",
   		app: "MICROSERVICE-PROVIDER-USER",
   		appGroupName: null,
   		ipAddr: "192.168.31.58",
   		sid: "na",
   		homePageUrl: "http://192.168.31.58:8000/",
   		statusPageUrl: "http://192.168.31.58:8000/info",
   		healthCheckUrl: "http://192.168.31.58:8000/health",
   		secureHealthCheckUrl: null,
   		vipAddress: "microservice-provider-user",
   		secureVipAddress: "microservice-provider-user",
   		countryId: 1,
   		dataCenterInfo: {
   			@class: "com.netflix.appinfo.InstanceInfo$DefaultDataCenterInfo",
   			name: "MyOwn"
   		},
   		hostName: "192.168.31.58",
   		status: "UP",
   		leaseInfo: {
   			renewalIntervalInSecs: 30,
   			durationInSecs: 90,
   			registrationTimestamp: 1563685921736,
   			lastRenewalTimestamp: 1563686401290,
   			evictionTimestamp: 0,
   			serviceUpTimestamp: 1563685921035
   		},
   		isCoordinatingDiscoveryServer: false,
   		metadata: {
   			my - metadata: "我自定义的元数据"
   		},
   		lastUpdatedTimestamp: 1563685921736,
   		lastDirtyTimestamp: 1563685920502,
   		actionType: "ADDED",
   		asgName: null,
   		overriddenStatus: "UNKNOWN"
   	},
   	serviceId: "MICROSERVICE-PROVIDER-USER"
   }]
   

   可以看到，使用DiscoveryClient的API获得了用户微服务的各种信息，其中包括标准元数据和自定义元数据。例如IP、端口等信息都是标准元数据，用于服务之间的调用；同时，自定义的元数据my-metadata，也可通过客户端查询到，但是并不会改变客户端的行为。

Eureka Server提供了一些REST端点。非JVM的微服务可使用这些REST端点操作Eureka，从而实现注册与发现。事实上，前文所讲的Eureka Client就是一个使用Java写的、操作这些REST端点的类库。也可分析这些REST端点，编写其他语言的Eureka Client。

下表是Eureka提供的REST端点，可以使用XML或者JSON与这些端点通信，默认是XML。