Ribbon简介

Ribbon则是一个客户端侧负载均衡组件——通俗地说，就是集成在客户端（服务消费者一侧），并提供负载均衡算法的一个组件。

引入Ribbon

在Spring Cloud中，当Ribbon与Eureka配合使用时，Ribbon可自动从Eureka Server获取服务提供者地址列表，并基于负载均衡算法，选择其中一个服务提供者实例。下图展示了Ribbon与Eureka配合使用时的大致架构。

Ribbon入门

1.添加父类pom.xml

<?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.bruobuqi</groupId>
    <artifactId>robbin</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>pom</packaging>

    <name>robbin</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.3.RELEASE</version>
        <relativePath/>
    </parent>

    <modules>
        <module>eurekaserver</module>
        <module>eurekaclient</module>
        <module>eurekaclient2</module>
        <module>ribbonclient</module>

    </modules>

    <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>Finchley.RELEASE</spring-cloud.version>
    </properties>

    <dependencies>
        <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>

2.新建一个spring-boot工程

ribbon-client

在它的pom.xml继承了父pom文件，并引入了以下依赖：

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.bruobuqi</groupId>
    <artifactId>ribbonclient</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>
    <name>ribbonclient</name>
    <description>Demo project for Spring Boot</description>


    <parent>
        <groupId>com.bruobuqi</groupId>
        <artifactId>robbin</artifactId>
        <version>0.0.1-SNAPSHOT</version>
    </parent>

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </dependency>
    </dependencies>
</project>

3.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：

server:
  port: 8766

spring:
  application:
    name: ribbon-client

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/

4.在工程的启动类中,通过@EnableDiscoveryClient向服务中心注册；

package com.bruobuqi;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

@SpringBootApplication
@EnableEurekaClient
@EnableDiscoveryClient
public class RibbonApplication {

    public static void main(String[] args) {
        SpringApplication.run(RibbonApplication.class, args);
    }

}

5.新建一个MyConfiger配置类并且向程序的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。（RestTemplate— 用更优雅的方式发HTTP请求(RestTemplate详解)）

package com.bruobuqi.config;

import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.client.RestTemplate;

@Configuration
public class MyConfiger {
    @Bean
    @LoadBalanced
    RestTemplate restTemplate() {
        return new RestTemplate();
    }
}

6.新建一个controller用来调用restTemplate

package com.bruobuqi.config;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

@RestController
public class AdminController {
    @Autowired
    RestTemplate restTemplate;
    @GetMapping(value = "/hi")
    public String hi(@RequestParam String name) {
        return hiService( name );
    }




        public String hiService(String name) {
            return restTemplate.getForObject("http://service-client/hi?name="+name,String.class);
        }

}

7.浏览器输入

http://localhost:8766/hi?name=nihao

页面交替显示

hi nihao ,i am from port:8764

hi nihao ,i am from port:8763