【前面的话】书接上文，本文的某些知识依赖我的上一篇文章：SpringCloud之Eureka，如果没有看过可以先移步去看一下。另外在微服务架构中，业务都会被拆分成一个个独立的服务，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。在这一篇文章首先讲解下基于ribbon+rest。

壹、Ribbon简介

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

贰、准备工作

新建一个ribbon子工程lovin-ribbon-client，用于后面的操作。下面是主要的pom依赖

<parent>
        <artifactId>lovincloud</artifactId>
        <groupId>com.eelve.lovincloud</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>lovin-ribbon-client</artifactId>
    <packaging>jar</packaging>
    <name>ribbonclient</name>
    <version>0.0.1</version>
    <description>ribbon的client</description>

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-security</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

这里为了安全，我这里还是添加spring-boot-starter-security

server:
  port: 8805   # 服务端口号
spring:
  application:
    name: lovinribbonclient     # 服务名称
  security:
    basic:
      enabled: true
    user:
      name: lovin
      password: ${REGISTRY_SERVER_PASSWORD:lovin}
eureka:
  client:
    serviceUrl:
      defaultZone: http://lovin:lovin@localhost:8881/eureka/   # 注册到的eureka服务地址

配置spring-boot-starter-security，这里为了方便我这里放开所有请求

package com.eelve.lovin.cofig;

import org.springframework.context.annotation.Configuration;
import org.springframework.core.annotation.Order;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;

/**
 * @ClassName SecurityConfig
 * @Description TDO
 * @Author zhao.zhilue
 * @Date 2019/8/16 14:12
 * @Version 1.0
 **/
@Configuration
@Order(0)
public class WebSecurityConfig extends WebSecurityConfigurerAdapter {

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http.authorizeRequests().anyRequest().permitAll()
                .and().csrf().disable();
    }
}

然后向程序的ioc容器中注入一个bean: restTemplate;并通过@LoadBalanced注解表明这个restRemplate开启负载均衡的功能。

package com.eelve.lovin;

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.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

/**
 * @ClassName LovinRibbonClientApplication
 * @Description TDO
 * @Author zhao.zhilue
 * @Date 2019/8/15 16:59
 * @Version 1.0
 **/
@SpringBootApplication
@EnableDiscoveryClient
public class LovinRibbonClientApplication {

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

    @Bean
    @LoadBalanced
    RestTemplate restTemplate() {
        return new RestTemplate();
    }
}

然后编写一个HelloService

package com.eelve.lovin.service;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;

/**
 * @ClassName HelloService
 * @Description TDO
 * @Author zhao.zhilue
 * @Date 2019/8/15 17:02
 * @Version 1.0
 **/
@Service
public class HelloService {
    @Autowired
    RestTemplate restTemplate;

    public String getHello() {
        //这里的**lovineurkaclient**是我上一篇文章新建的eureka客户端的名称
        return restTemplate.getForObject("http://lovineurkaclient/hello",String.class);
    }
}

再编写一个HelloController

package com.eelve.lovin.controller;

import com.eelve.lovin.service.HelloService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

/**
 * @ClassName HelloController
 * @Description TDO
 * @Author zhao.zhilue
 * @Date 2019/8/15 17:05
 * @Version 1.0
 **/
@RestController
public class HelloController {

    @Autowired
    HelloService helloService;

    @RequestMapping("hello")
    public String hello(){
        return helloService.getHello();
    }
}