Ribbon是一个负载均衡客户端,可以很好的控制http和tcp的一些行为,一般都是Ribbon搭配Feign一起使用;Feign默认集成了ribbon

添加feign的依赖

compile('io.github.openfeign:feign-core:9.5.0')     compile('io.github.openfeign:feign-jackson:9.5.0')     compile('io.github.openfeign:feign-ribbon:9.5.0')     

build.gradle文件内容:

apply plugin: 'java' apply plugin: 'eclipse'  group = 'org.wjw.standardribbon' version = '1.0.0-SNAPSHOT' sourceCompatibility = 1.8 [compileJava, compileTestJava]*.options*.encoding = 'UTF-8'  repositories {   mavenLocal()   maven{ url "http://SVN:8081/nexus/content/groups/public"}   mavenCentral()   jcenter() }   dependencies { 	compile('org.slf4j:slf4j-api') 	compile('org.slf4j:slf4j-log4j12:1.7.25') 	compile('commons-logging:commons-logging:1.2') 	 	compile('io.github.openfeign:feign-core:9.5.0') 	compile('io.github.openfeign:feign-jackson:9.5.0') 	compile('io.github.openfeign:feign-ribbon:9.5.0') }  

创建一个 Java Application 项目

执行: gradle init --type java-library

• Feign声明式服务消费端接口
  RemoteService接口中定义了一个名为getAdd的方法

package org.wjw.standardribbon.service;  import feign.Headers; import feign.Param; import feign.RequestLine;  public interface RemoteService { 	/** 	GET /add?a=1&b=2 HTTP/1.1 	Content-Type: application/json 	Accept: application/json 	User-Agent: Java/1.8.0_121 	Host: 192.168.2.113:8861 	Connection: keep-alive 	*/ 	@Headers({ "Content-Type: application/json", "Accept: application/json" }) 	@RequestLine("GET /add?a={a}&b={b}") 	int getAdd(@Param("a") int a, @Param("b") int b); 	 }  

• 编写ribbon.properties,该文件位于src/main/resources下

#所有的key都以service-one开头,表明这些配置项作用于名为service-one的服务 service-one.ribbon.MaxAutoRetries=1 service-one.ribbon.MaxAutoRetriesNextServer=1 service-one.ribbon.OkToRetryOnAllOperations=true service-one.ribbon.ServerListRefreshInterval=2000 service-one.ribbon.ConnectTimeout=3000 service-one.ribbon.ReadTimeout=3000 service-one.ribbon.listOfServers=192.168.2.113:8861,192.168.2.114:8861 service-one.ribbon.EnablePrimeConnections=false  config-server.ribbon.MaxAutoRetries=1 config-server.ribbon.MaxAutoRetriesNextServer=1 config-server.ribbon.OkToRetryOnAllOperations=true config-server.ribbon.ServerListRefreshInterval=2000 config-server.ribbon.ConnectTimeout=3000 config-server.ribbon.ReadTimeout=3000 config-server.ribbon.listOfServers=192.168.2.114:7001 config-server.ribbon.EnablePrimeConnections=false   

> 现在来看ribbon.properties中的配置项 所有的key都以service-one开头,表明这些配置项作用于名为service-one的服务.其实就是与之前绑定RemoteService接口的URL地址的schema相对应.

> 重点看ribbon.properties文件里的service-one.ribbon.listOfServers配置项,该配置项指定了服务生产端的真实地址. > 与RemoteService接口绑定的URL地址是"http://service-one/",

> 在调用时会被替换为http://192.168.2.113:8861/或http://192.168.2.114:8861/,再与接口中@RequestLine指定的地址进行拼接,得到最终请求地址. > 本例中最终请求地址为http://192.168.2.113:8861/add或http://192.168.2.114:8861/add

> 由于使用的ribbon,所以feign不再需要配置超时时长,重试策略.ribbon提供了更为完善的策略实现.

• 本例中,服务端是一个简单的spring mvc,实现如下:

package org.wjw.cloud.service.controller;  import org.apache.log4j.Logger; 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.RequestMapping; import org.springframework.web.bind.annotation.RequestMethod; import org.springframework.web.bind.annotation.RequestParam; import org.springframework.web.bind.annotation.RestController;  @RestController public class ComputeController { 	private final Logger logger = Logger.getLogger(getClass());  	@Autowired 	private DiscoveryClient client;  	@RequestMapping(value = "/add", method = RequestMethod.GET) 	public int add(@RequestParam int a, @RequestParam int b) { 		int r = a + b;  		ServiceInstance instance = client.getInstances(client.getServices().get(0)).get(0); 		logger.info("/add, host:" + instance.getHost() + ", service_id:" + instance.getServiceId() + ", result:" + r); 		return r; 	}  }  

> 将服务生产端部署到Eureka中,在8861端口运行

• Java启动APP

package org.wjw.standardribbon;  import org.wjw.standardribbon.model.User; import org.wjw.standardribbon.service.PropService; import org.wjw.standardribbon.service.RemoteService;  import com.netflix.client.ClientFactory; import com.netflix.client.config.IClientConfig; import com.netflix.config.ConfigurationManager; import com.netflix.loadbalancer.ILoadBalancer; import com.netflix.loadbalancer.RandomRule; import com.netflix.loadbalancer.ZoneAwareLoadBalancer;  import feign.Feign; import feign.jackson.JacksonDecoder; import feign.jackson.JacksonEncoder; import feign.ribbon.LBClient; import feign.ribbon.LBClientFactory; import feign.ribbon.RibbonClient;  public class StdRibbon { 	public static void main(String[] args) throws Exception { 		ConfigurationManager.loadPropertiesFromResources("ribbon.properties");  		RibbonClient client = RibbonClient.builder().lbClientFactory(new LBClientFactory() { 			@Override 			public LBClient create(String clientName) { 				IClientConfig config = ClientFactory.getNamedConfig(clientName); 				ILoadBalancer lb = ClientFactory.getNamedLoadBalancer(clientName); 				ZoneAwareLoadBalancer zb = (ZoneAwareLoadBalancer) lb; 				zb.setRule(new RandomRule()); 				return LBClient.create(lb, config); 			} 		}).build();  		/* 		  重点看ribbon.properties文件里的service-one.ribbon.listOfServers配置项,该配置项指定了服务生产端的真实地址.                        与RemoteService接口绑定的URL地址是"http://service-one/",                        在调用时会被替换为http://192.168.2.113:8861/或http://192.168.2.114:8861/,再与接口中@RequestLine指定的地址进行拼接,得到最终请求地址                       本例中最终请求地址为"http://192.168.2.113:8861/add"或"http://192.168.2.114:8861/add" 		*/ 		RemoteService service = Feign.builder().client(client).encoder(new JacksonEncoder()) 				.decoder(new JacksonDecoder()).target(RemoteService.class, "http://service-one/");  		/** 		 * 调用测试 		 */ 		for (int i = 1; i <= 10; i++) { 			int result = service.getAdd(1, 2); 			System.out.println("result:" + result); 		}  	} }  

> 首先利用com.netflix.config.ConfigurationManager读取配置文件ribbon.properties,该文件位于src/main/resources下.
重点在于通过RibbonClient.create()使得Feign对象获得了Ribbon的特性.之后通过encoder,decoder设置编码器与解码器,并通过target方法将之前定义的接口RemoteService与一个URL地址http://service-one/进行了绑定.

启动Spring Boot程序

执行: gradlew bootRun > 默认端口号是:8080

在浏览器里测试

> 输入:http://127.0.0.1:8080/add?a=1&b=2

> 返回: 3