springCloud(4)---服务调用方式1：ribbon+restTemplate

在微服务架构中,应用被拆分为一个独立的服务,服务与服务之间的通讯是基于httpRestful

springCloud中有2种服务调用方式：一种是ribbon+restTemplate，一种是feign

本章讲解如何使用ribbon+restTemplate调用服务,以及实现负载均衡

第一步、创建一个maven工程,工程名为eureka-ribbon,结构图如下：

第二步、修改pom.xml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>
   <parent>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-parent</artifactId>
      <version>2.1.3.RELEASE</version>
      <relativePath/> <!-- lookup parent from repository -->
   </parent>
   <groupId>com.cn</groupId>
   <artifactId>eureka-ribbon</artifactId>
   <version>0.0.1-SNAPSHOT</version>
   <name>eureka-ribbon</name>
   <description>Demo project for Spring Boot</description>

   <properties>
      <java.version>1.8</java.version>
      <spring-cloud.version>Greenwich.SR1</spring-cloud.version>
   </properties>

   <dependencies>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter</artifactId>
      </dependency>

      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-test</artifactId>
         <scope>test</scope>
      </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-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>${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>

第三步、修改application.yml文件,内容如下：

server:
  port: 8503
spring:
  application:
    name: service-ribbon
eureka:
  client:
    service-url:
      defaultZone: http://localhost:8501/eureka/

第四步、新建包com.cn.service,然后在该包下新建类RibbonService

package com.cn.service;

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

/**
 * 写一个测试服务类,通过之前注入到IOC容器中的restTemplate来消费
 * eureka-client项目中的service-client1服务的/hello接口
 * 本示例：直接用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
 * */
@Service
public class RibbonService {
    @Autowired
    RestTemplate restTemplate;

    public String ribbonService(String name){
        return restTemplate.getForObject("http://SERVICE-CLIENT1/hello?name="+name,String.class);
    }
}

第五步、新建包com.cn.controller,然后在该包下新建类RibbonController

package com.cn.controller;

import com.cn.service.RibbonService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class RibbonController {
    @Autowired
    RibbonService ribbonService;
    @RequestMapping("/hi")
    public String test(@RequestParam String name){
        return ribbonService.ribbonService(name);
    }
}

第六步、修改启动类,代码如下：

package com.cn.eurekaribbon;

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

@SpringBootApplication
@EnableEurekaClient
@EnableDiscoveryClient //通过该注解向服务中心注册
@ComponentScan({"com.cn.service","com.cn.controller"})
public class EurekaRibbonApplication {

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

   @Bean  //向ioc容器中注入一个bean
   @LoadBalanced  //表明这个restTemplate开启了负载均衡的功能
   RestTemplate restTemplate(){
      return new RestTemplate();
   }

}

第七步、测试

修改eureka-client类的配置文件application.yml的端口号为8504和8506,8502端口启动一次启动类、修改端口8504然后启动一次启动类、修改端口8506然后启动一次启动类,如下

先启动eureka-server注册中心,再逐个启动eureka-client,再启动eureka-ribbon类，然后,打开浏览器测试,如下：

再次刷新,显示如下：

每次刷新,调用的eureka-client不同,说明实现负载均衡成功

springCloud(4)---服务调用方式1：ribbon+restTemplate

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