前面介紹過dubbo遠端介面呼叫的簡單使用，這裡我們將開始學習如何使用springcloud微服務架構中的服務註冊與發現。

一，eureka-server

eureka分為服務端和客戶端兩部分， eureka server是一個服務註冊中心，類似於zookeeper，當然，也可以使用zookeeper代替，後面會詳細說明。 首先，新建一個maven springboot應用，這裡命名為eureka-server 1，新增依賴包

<dependency>
	<groupId>org.springframework.cloud</groupId>
	<artifactId>spring-cloud-starter-eureka-server</artifactId>
</dependency>
 

2，新增配置檔案application.properties

#應用名稱
spring.application.name=eureka-server
#服務埠
server.port=8080
#例項ip地址
eureka.instance.hostname=localhost
#設定當前的eureka服務禁止被當做客戶端註冊
eureka.client.register-with-eureka=false
eureka.client.fetch-registry=false
#設定服務發現地址
eureka.client.serviceUrl.defaultZone=http://localhost:${server.port}/eureka/
 

3，啟動類Application.java添加註解@EnableEurekaServer

package com.example;

import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;

@EnableEurekaServer
@SpringBootApplication
public class Application {

	public static void main(String[] args) {
		new SpringApplicationBuilder(Application.class).web(true).run(args);
	}

}
 

4，啟動訪問，此時還沒有任何服務註冊

二，eureka-client 還是新建一個maven springboot應用，這裡命名為eureka-client 1，新增依賴包

<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>

2，新增application.properties配置

spring.application.name=eureka-client
server.port=8081
eureka.client.serviceUrl.defaultZone=http://localhost:8080/eureka

3，啟動類Application.java添加註解註冊服務@EnableDiscoveryClient

package com.example;

import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;

@EnableDiscoveryClient
@SpringBootApplication
public class Application {

	public static void main(String[] args) {
		new SpringApplicationBuilder(Application.class).web(true).run(args);
	}

}

4，啟動後重新整理eureka-server介面，會發現多了一個註冊的客戶端例項eureka-client
三，feign

上面簡單演示了使用eureka發現和註冊服務，下面我們來看，如何使用feign來實現遠端介面的呼叫。

還是新建一個maven springboot應用，這裡命名為eureka-feign

1，新增依賴包

<dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-eureka</artifactId>
</dependency>
<dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-feign</artifactId>
</dependency>
<dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
</dependency>

2，新增配置application.properties

spring.application.name=eureka-feign
server.port=8082
eureka.client.serviceUrl.defaultZone=http://localhost:8080/eureka
feign.httpclient.enabled=true
feign.compression.request.enabled=true
feign.compression.request.mime-types=application/json
feign.compression.request.min-request-size=2048
feign.compression.response.enabled=true

3，Application.java啟動類開啟註解@EnableFeignClients

package com.example;

import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.netflix.feign.EnableFeignClients;
import org.springframework.context.annotation.Bean;

import feign.Request;

@EnableFeignClients
@EnableDiscoveryClient
@SpringBootApplication
public class Application {

	public static void main(String[] args) {
		new SpringApplicationBuilder(Application.class).web(true).run(args);
	}

	/**
	 * 自定義feign連線超時時間
	 * @return
	 */
	@Bean
    Request.Options feignOptions() {
        return new Request.Options(/**connectTimeoutMillis**/1000 * 1000, /** readTimeoutMillis **/1000 * 1000);
    }
}

4，啟動，重新整理eureka-server介面，可以看到服務已經註冊成功

5，新增測試類，從eureka-feign服務中呼叫eureka-client中的介面

(1) 在eureka-feign中新增TestController.java

package com.example;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class TestController {

    @Autowired
    TestClient testClient;
    
    @RequestMapping(value="/test",method=RequestMethod.GET)
    public String test() {
    	String msg = testClient.test();
    	return msg;
    }

}

(2) 定義介面TestClient.java，指定實現服務的@FeignClient("eureka-client")

package com.example;

import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

@FeignClient("eureka-client")
public interface TestClient {

    @RequestMapping(value="/test",method=RequestMethod.GET)
    String test();

}

(3) 在eureka-client中新增介面實現

package com.example;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class TestController {

    @RequestMapping(value="/test",method=RequestMethod.GET)
    public String test() {
        String msg = "this service is eureka-client";
        return msg;
    }

}

注意：feign介面呼叫使用的仍然是http協議，且支援spring註解，引數需與呼叫方一致。

接下來啟動服務，訪問http://localhost:8082/test，檢視測試結果：

6，feign還支援負載均衡，不需要額外配置，繼續儲存服務開啟狀態，修改eureka-client的port=8083，然後啟動

此時有兩個eureka-client例項提供服務：

再次訪問http://localhost:8082/test，這裡共測試了4次，檢視控制檯日誌，埠為8081和埠為8083的服務各呼叫了兩次。

8081埠日誌：

2017-08-09 16:50:24.671  INFO 3104 --- [           main] com.netflix.discovery.DiscoveryClient    : Saw local status change event StatusChangeEvent [timestamp=1502268624671, current=UP, previous=STARTING]
2017-08-09 16:50:24.674  INFO 3104 --- [nfoReplicator-0] com.netflix.discovery.DiscoveryClient    : DiscoveryClient_EUREKA-CLIENT/PC-201611261236:eureka-client:8081: registering service...
2017-08-09 16:50:24.739  INFO 3104 --- [nfoReplicator-0] com.netflix.discovery.DiscoveryClient    : DiscoveryClient_EUREKA-CLIENT/PC-201611261236:eureka-client:8081 - registration status: 204
2017-08-09 16:50:24.823  INFO 3104 --- [           main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s): 8081 (http)
2017-08-09 16:50:24.825  INFO 3104 --- [           main] .s.c.n.e.s.EurekaAutoServiceRegistration : Updating port to 8081
2017-08-09 16:50:24.830  INFO 3104 --- [           main] com.example.Application                  : Started Application in 8.949 seconds (JVM running for 9.584)
2017-08-09 16:53:24.596  INFO 3104 --- [nio-8081-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring FrameworkServlet 'dispatcherServlet'
2017-08-09 16:53:24.598  INFO 3104 --- [nio-8081-exec-1] o.s.web.servlet.DispatcherServlet        : FrameworkServlet 'dispatcherServlet': initialization started
2017-08-09 16:53:24.634  INFO 3104 --- [nio-8081-exec-1] o.s.web.servlet.DispatcherServlet        : FrameworkServlet 'dispatcherServlet': initialization completed in 36 ms
--------------this service is eureka-client
--------------this service is eureka-client
2017-08-09 16:55:24.319  INFO 3104 --- [trap-executor-0] c.n.d.s.r.aws.ConfigClusterResolver      : Resolving eureka endpoints via configuration

8083埠日誌：

2017-08-09 16:54:02.333  INFO 4640 --- [           main] com.netflix.discovery.DiscoveryClient    : Saw local status change event StatusChangeEvent [timestamp=1502268842333, current=UP, previous=STARTING]
2017-08-09 16:54:02.336  INFO 4640 --- [nfoReplicator-0] com.netflix.discovery.DiscoveryClient    : DiscoveryClient_EUREKA-CLIENT/PC-201611261236:eureka-client:8083: registering service...
2017-08-09 16:54:02.413  INFO 4640 --- [nfoReplicator-0] com.netflix.discovery.DiscoveryClient    : DiscoveryClient_EUREKA-CLIENT/PC-201611261236:eureka-client:8083 - registration status: 204
2017-08-09 16:54:02.466  INFO 4640 --- [           main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s): 8083 (http)
2017-08-09 16:54:02.467  INFO 4640 --- [           main] .s.c.n.e.s.EurekaAutoServiceRegistration : Updating port to 8083
2017-08-09 16:54:02.477  INFO 4640 --- [           main] com.example.Application                  : Started Application in 8.863 seconds (JVM running for 9.467)
2017-08-09 16:54:05.998  INFO 4640 --- [nio-8083-exec-2] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring FrameworkServlet 'dispatcherServlet'
2017-08-09 16:54:05.999  INFO 4640 --- [nio-8083-exec-2] o.s.web.servlet.DispatcherServlet        : FrameworkServlet 'dispatcherServlet': initialization started
2017-08-09 16:54:06.027  INFO 4640 --- [nio-8083-exec-2] o.s.web.servlet.DispatcherServlet        : FrameworkServlet 'dispatcherServlet': initialization completed in 28 ms
--------------this service is eureka-client
--------------this service is eureka-client
2017-08-09 16:59:01.991  INFO 4640 --- [trap-executor-0] c.n.d.s.r.aws.ConfigClusterResolver      : Resolving eureka endpoints via configuration

四，上面我們提到過，服務註冊不一定要用eureka，下面我們使用zookeeper來代替使用。

首先，對eureka-feign和eureka-client進行改造，主要是配置修改。

1，修改依賴包，將eureka包註釋掉，新增zookeeper依賴

<!--         <dependency> -->
<!--             <groupId>org.springframework.cloud</groupId> -->
<!--             <artifactId>spring-cloud-starter-eureka</artifactId> -->
<!--         </dependency> -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-zookeeper-all</artifactId>
        </dependency>

2，將application.properties中的eureka服務地址註釋掉

#eureka.client.serviceUrl.defaultZone=http://localhost:8080/eureka

3，新增bootstrap.properties，指定zookeeper地址

spring.cloud.zookeeper.connectString=localhost:2181
spring.cloud.zookeeper.discovery.instancePort=${server.port}

4，其他配置都不變，開啟zookeeper，然後同時開啟eureka-feign和eureka-client

訪問http://localhost:8082/test，同樣可以得到相同的測試結果：