前面介绍过dubbo远程接口调用的简单使用，这里我们将开始学习如何使用springcloud微服务架构中的服务注册与发现。

一，eureka-server

eureka分为服务端和客户端两部分， eureka server是一个服务注册中心，类似于zookeeper，当然，也可以使用zookeeper代替，后面会详细说明。
首先，新建一个maven springboot应用，这里命名为eureka-server
1，添加依赖包 
<dependency>
	<groupId>org.springframework.cloud</groupId>
	<artifactId>spring-cloud-starter-eureka-server</artifactId>
</dependency>
2，添加配置文件application.properties 
#应用名称
spring.application.name=eureka-server
#服务端口
server.port=8080
#实例ip地址
eureka.instance.hostname=localhost
#设置当前的eureka服务禁止被当做客户端注册
eureka.client.register-with-eureka=false
eureka.client.fetch-registry=false
#设置服务发现地址
eureka.client.serviceUrl.defaultZone=http://localhost:${server.port}/eureka/
3，启动类Application.java添加注解@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，启动访问，此时还没有任何服务注册


二，eureka-client
还是新建一个maven springboot应用，这里命名为eureka-client
1，添加依赖包 
<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，添加application.properties配置 
spring.application.name=eureka-client
server.port=8081
eureka.client.serviceUrl.defaultZone=http://localhost:8080/eureka
3，启动类Application.java添加注解注册服务@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，启动后刷新eureka-server界面，会发现多了一个注册的客户端实例eureka-client

三，feign

上面简单演示了使用eureka发现和注册服务，下面我们来看，如何使用feign来实现远程接口的调用。

还是新建一个maven springboot应用，这里命名为eureka-feign

1，添加依赖包

<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，添加配置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启动类开启注解@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);
	}

	/**
	 * 自定义feign连接超时时间
	 * @return
	 */
	@Bean
    Request.Options feignOptions() {
        return new Request.Options(/**connectTimeoutMillis**/1000 * 1000, /** readTimeoutMillis **/1000 * 1000);
    }
}
4，启动，刷新eureka-server界面，可以看到服务已经注册成功

5，添加测试类，从eureka-feign服务中调用eureka-client中的接口

(1) 在eureka-feign中添加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) 定义接口TestClient.java，指定实现服务的@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中添加接口实现

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接口调用使用的仍然是http协议，且支持spring注解，参数需与调用方一致。

接下来启动服务，访问http://localhost:8082/test，查看测试结果：

6，feign还支持负载均衡，不需要额外配置，继续保存服务开启状态，修改eureka-client的port=8083，然后启动

此时有两个eureka-client实例提供服务：

再次访问http://localhost:8082/test，这里共测试了4次，查看控制台日志，端口为8081和端口为8083的服务各调用了两次。

8081端口日志：

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端口日志： 

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，上面我们提到过，服务注册不一定要用eureka，下面我们使用zookeeper来代替使用。

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

1，修改依赖包，将eureka包注释掉，添加zookeeper依赖

<!--         <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，将application.properties中的eureka服务地址注释掉 

#eureka.client.serviceUrl.defaultZone=http://localhost:8080/eureka
3，添加bootstrap.properties，指定zookeeper地址 

spring.cloud.zookeeper.connectString=localhost:2181
spring.cloud.zookeeper.discovery.instancePort=${server.port}
4，其他配置都不变，开启zookeeper，然后同时开启eureka-feign和eureka-client

访问http://localhost:8082/test，同样可以得到相同的测试结果：




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