（二）spring-cloud入门学习：服务消费rest+ribbon

前面讲了如何将服务注册到Eureka服务端，为了保证服务的高可用，同一个服务都会采用集群形式注册多个节点，那如何去消费这些服务？通过IP+端口的形式明显不合理，那就需要通过服务应用名来进行访问，同时需要能够将请求均衡转发到各节点。而Ribbon就很好地解决了这个问题，Ribbon是一个负载均衡客户端，可以很好的控制htt和tcp的一些行为。

1. 创建一个服务消费者工程eureka_ribbon， pom.xml文件如下：

<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>com.kevin</groupId> <artifactId>eureka_ribbon</artifactId> <version>0.0.1-SNAPSHOT</version> <packaging>jar</packaging> <name>eureka_ribbon</name> <url>http://maven.apache.org</url> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> </properties> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.1.4.RELEASE</version> </parent> <dependencies> <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> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId> </dependency> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-netflix-ribbon</artifactId> </dependency> </dependencies> <dependencyManagement> <dependencies> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-dependencies</artifactId> <version>Greenwich.SR1</version> <type>pom</type> <scope>import</scope> </dependency> </dependencies> </dependencyManagement> </project>

2. application.properties

spring.application.name=eurekaRibbon server.port=9201 #注册到eureka eureka.client.serviceUrl.defaultZone=http://localhost:9101/eureka/

3. Application.java 使用@EnableDiscoveryClient开启服务发现，同时需要申明RestTemplate。

package com.kevin.eureka_ribbon; import org.springframework.boot.WebApplicationType; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.boot.builder.SpringApplicationBuilder; import org.springframework.cloud.client.discovery.EnableDiscoveryClient; import org.springframework.cloud.client.loadbalancer.LoadBalanced; import org.springframework.context.annotation.Bean; import org.springframework.web.client.RestTemplate; @SpringBootApplication @EnableDiscoveryClient public class Application { public static void main( String[] args ) { new SpringApplicationBuilder(Application.class) .web(WebApplicationType.SERVLET).run(args); } @Bean @LoadBalanced RestTemplate restTemplate() { return new RestTemplate(); } }

4. 创建一个service，HelloService.java 使用RestTemplate进行服务调用

package com.kevin.eureka_ribbon.service; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Service; import org.springframework.web.client.RestTemplate; @Service public class HelloService { @Autowired private RestTemplate restTemplate; public String sayHello() { return restTemplate.getForObject("http://eurekaClient/sayHello", String.class); } }

备注：通过服务注册的name来访问api，该name不能包含下划线，否则报错Request URI does not contain a valid hostname.

5. 创建一个api对外访问，HelloController.java

package com.kevin.eureka_ribbon.controller; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; import com.kevin.eureka_ribbon.service.HelloService; @RestController public class HelloController { @Autowired private HelloService helloService; @RequestMapping("sayHello") public String sayHello() { return helloService.sayHello(); } }

6. 启动项目并访问http://127.0.0.1:9201/sayHello

能够正常访问结果，同时查看两个服务client的后台，请求7次，eureka_client9102收到4次请求，eureka_client9103收到3次请求，说明ribbon会将请求负载均衡到各服务端。