（七）spring cloud微服务分布式云架构-服务消费者（rest+ribbon）

- 日理万妓 2022-03-09 20:06 239阅读 0赞

一、ribbon简介

Ribbon is a client side load balancer which gives you a lot of control over the behaviour of HTTP and TCP clients. Feign already uses Ribbon, so if you are using @FeignClient then this section also applies.

—–摘自官网 Spring Cloud大型企业分布式微服务云架构源码请加一七九一七四三三八零

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。Feign默认集成了ribbon。

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

二、建一个服务消费者

重新新建一个spring-boot工程，取名为：service-ribbon;

在它的pom.xml文件分别引入起步依赖spring-cloud-starter-eureka、spring-cloud-starter-ribbon、spring-boot-starter-web，代码如下：

<?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.forezp</groupId>
        <artifactId>service-ribbon</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <packaging>jar</packaging>
     
        <name>service-ribbon</name>
        <description>Demo project for Spring Boot</description>
     
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>1.5.2.RELEASE</version>
            <relativePath/> 
        </parent>
     
        <properties>
            <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
            <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
            <java.version>1.8</java.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.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>
        </dependencies>
     
        <dependencyManagement>
            <dependencies>
                <dependency>
                    <groupId>org.springframework.cloud</groupId>
                    <artifactId>spring-cloud-dependencies</artifactId>
                    <version>Dalston.RC1</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>
     
        <repositories>
            <repository>
                <id>spring-milestones</id>
                <name>Spring Milestones</name>
                <url>https://repo.spring.io/milestone</url>
                <snapshots>
                    <enabled>false</enabled>
                </snapshots>
            </repository>
        </repositories>
    </project>

在工程的配置文件指定服务的注册中心地址为http:/ /localhost:8761/eureka/，程序名称为 service-ribbon，程序端口为8764。配置文件application.yml如下：

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

在工程的启动类中,通过@EnableDiscoveryClient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。

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

写一个测试类HelloService，通过之前注入ioc容器的restTemplate来消费service-hi服务的“/hi”接口，在这里我们直接用的程序名替代了具体的url地址，在ribbon中它会根据服务名来选择具体的服务实例，根据服务实例在请求的时候会用具体的url替换掉服务名，代码如下：

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

写一个controller，在controller中用调用HelloService 的方法，代码如下：

/**
     * Created by fangzhipeng on 2017/4/6.
     */
    @RestController
    public class HelloControler {
     
        @Autowired
        HelloService helloService;
        @RequestMapping(value = "/hi")
        public String hi(@RequestParam String name){
            return helloService.hiService(name);
        }
     
     
    }

在浏览器上多次访问http:/ /localhost:8764/hi?name=forezp，浏览器交替显示：

hi forezp,i am from port:8762
     
    hi forezp,i am from port:8763

这说明当我们通过调用restTemplate.getForObject(“http:/ /SERVICE-HI/hi?name=“+name,String.class)方法时，已经做了负载均衡，访问了不同的端口的服务实例。