SpringCloud-服务的消费者(rest+ribbon)

在微服务架构中，业务都会被拆分成一个独立的服务，服务与服务的通讯是基于http restful的。Spring Cloud有两种服务调用方式，一种是ribbon+restTemplate,另一种是feign，先来说下ribbon+rest

Ribbon简介

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。Feign默认集成了ribbon
实现负载均衡，我们可以通过服务器端和客户端做负载均衡。服务器端做负载均衡，可以使用Nginx。而客户端做负载均衡，就是客户端有一个组件，知道有哪些可用的微服务，实现一个负载均衡算法。
Ribbon工作流程主要分为两步:
第一：先选择Eureka Server，优先选择在同一个Zone且负载较少的Server
第二：再根据用户指定的策略，再从server取到的服务注册列表中选择一个地址。其中Ribbon提供了很多种策略，例如轮询round bin ，随机random，很具响应时间加权

Ribbon已经默认实现了这些配置bean
IClientConfig ribbonClientConfig: DefaultClientConfigImpl
IRule ribbonRule: ZoneAvoidanceRule
IPing ribbonPing: NoOpPing
ServerList ribbonServerList: ConfigurationBasedServerList
ServerListFilter ribbonServerListFilter: ZonePreferenceServerListFilter
ILoadBalancer ribbonLoadBalancer: ZoneAwareLoadBalancer

项目创建

新建一个Eureka Client项目

pom文件如下

<?xml version="1.0" encoding="UTF-8"?>
<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.SpringCloud</groupId>
   <artifactId>service-ribbon</artifactId>
   <version>0.0.1-SNAPSHOT</version>
   <packaging>jar</packaging>
 
   <name>service-ribbon</name>
   <description>service-ribbon-description</description>
 
   <parent>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-parent</artifactId>
      <version>1.5.13.RELEASE</version>
      <relativePath/> <!-- lookup parent from repository -->
   </parent>
 
   <properties>
      <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
      <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
      <java.version>1.8</java.version>
      <spring-cloud.version>Edgware.SR3</spring-cloud.version>
   </properties>
 
   <dependencies>
      <dependency>
         <groupId>org.springframework.cloud</groupId>
         <artifactId>spring-cloud-starter-eureka</artifactId>
      </dependency>
      <dependency>
         <groupId>org.springframework.cloud</groupId>
         <artifactId>spring-cloud-starter-ribbon</artifactId>
      </dependency>
      <dependency>
         <groupId>org.springframework.cloud</groupId>
         <artifactId>spring-cloud-starter-web</artifactId>
      </dependency>
 
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-test</artifactId>
         <scope>test</scope>
      </dependency>
   </dependencies>
 
   <dependencyManagement>
      <dependencies>
         <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-dependencies</artifactId>
            <version>${spring-cloud.version}</version>
            <type>pom</type>
            <scope>import</scope>
         </dependency>
      </dependencies>
   </dependencyManagement>
 
   <build>
      <plugins>
         <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
         </plugin>
      </plugins>
   </build>
 
 
</project>

application.yml如下

spring:
  application:
    name: service-ribbon
server:
  port: 8764
eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka/

项目启动类修改如下

@EnableDiscoveryClient
@SpringBootApplication
public class ServiceRibbonApplication {
 
   public static void main(String[] args) {
      SpringApplication.run(ServiceRibbonApplication.class, args);
   }
    
   @Bean
   @LoadBalanced
   RestTemplate restTemplate(){
      return new RestTemplate();
   }
}

通过@EurekaDiscoveryClient向服务中心注册；并且向程序的IOC注入一个bean：restTemplate；并通过@LoadBalanced注解表明这个restRemplate开启负载均衡的功能。

新建测试service

@Service
public class HelloService {
 
    @Autowired
    RestTemplate restTemplate;
 
    public String hiService(String name) {
        return restTemplate.getForObject("http://eureka-client/hello?name=" + name, String.class);
    }
}

新建测试controller

@RestController
public class HelloController {
 
    @Autowired
    HelloService helloService;
 
    @RequestMapping("/hi")
    public String hi(@RequestParam String name) {
        return helloService.hiService(name);
    }
 
}