Spring Cloud 入门教程2、服务消费者（Ribbon）
一、前言
1、什么是Ribbon
Ribbon是Netflix开源的实现了负载均衡等功能的RPC客户端。 支持HTTP、TCP、UDP协议，且有一定的容错、缓存等机制。
Spring Cloud基于Ribbon封装了Spring Cloud Ribbon，方便结合Eureka、Consul等服务治理框架使用。Ribbon的主要作用是：从服务器端拿到对应服务列表后以负载均衡的方式访问对应服务。
从这张图上来说，Ribbon主要是从Eureka拿到服务列表之后，以负载均衡的策略选择其中一台发起调用。
2、本篇环境信息
框架
版本
Spring Boot
2.0.0.RELEASE
Spring Cloud
Finchley.BUILD-SNAPSHOT
JDK
1.8.x
3、准备工作
Eureka服务端搭建
参考：https://ken.io/note/spring-cloud-eureka-quickstart
服务提供者搭建
参考：https://ken.io/note/spring-cloud-eureka-quickstart
项
说明
GroupId
io.ken.springcloud.testservice
ArtifactId
testservice
pom.xml、启动类（App.java）保持不变
二、服务提供者准备
1、配置Eureka地址
application.yml 配置
server:
port: 8602
spring:
application:
name: testservice
eureka:
client:
serviceUrl:
defaultZone: http://localhost:8800/eureka/
app:
ip: localhost
2、DTO准备
创建共用的ResponseDTO：Result.java
package io.ken.springcloud.testservice.model;
public class Result {
private int code;
private String message;
private Object content;
private String serviceName;
private String host;
public int getCode() {
return code;
}
public void setCode(int code) {
this.code = code;
}
public String getMessage() {
return message;
}
public void setMessage(String message) {
this.message = message;
}
public Object getContent() {
return content;
}
public void setContent(Object content) {
this.content = content;
}
public String getServiceName() {
return serviceName;
}
public void setServiceName(String serviceName) {
this.serviceName = serviceName;
}
public String getHost() {
return host;
}
public void setHost(String host) {
this.host = host;
}
}
创建Plus.java用作加法运算RequestDTO
package io.ken.springcloud.testservice.model;
public class Plus {
private int numA;
private int numB;
public int getNumA() {
return numA;
}
public void setNumA(int numA) {
this.numA = numA;
}
public int getNumB() {
return numB;
}
public void setNumB(int numB) {
this.numB = numB;
}
}
3、编写服务入口
创建服务入口 TestController.java
package io.ken.springcloud.testservice.controller;
import io.ken.springcloud.testservice.model.Plus;
import io.ken.springcloud.testservice.model.Result;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class TestController {
@Value("${spring.application.name}")
private String serviceName;
@Value("${app.ip}")
private String address;
@Value("${server.port}")
private String port;
@RequestMapping("/")
public Object index() {
Result result = new Result();
result.setServiceName(serviceName);
result.setHost(String.format("%s:%s", address, port));
result.setMessage("hello");
return result;
}
@RequestMapping("/plus")
public Object plus(Plus plus) {
Result result = new Result();
result.setServiceName(serviceName);
result.setHost(String.format("%s:%s", address, port));
result.setMessage("success");
result.setContent(plus.getNumA() + plus.getNumB());
return result;
}
}
4、访问测试
启动TestService
分别以端口8602,8603启动testservice。 此时testservice等于是在Eureka Server注册了两个实例
分别访问 http://localhost:8602 ，http://localhost:8603
将会看到以下信息：
http://localhost:8602
{
"code": 0,
"message": "success",
"content": 0,
"serviceName": "testservice",
"host": "localhost:8062"
}
http://localhost:8603
{
"code": 0,
"message": "success",
"content": 0,
"serviceName": "testservice",
"host": "localhost:8063"
}
三、服务消费者搭建（Ribbon）
1、创建Ribbon项目
创建一个Spring Boot工程
使用maven-archtype-quickstart模板创建项目
项
说明
GroupId
io.ken.springcloud.ribbonclient
ArtifactId
ribbonclient
在pom.xml加入相关依赖
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
配置启动类
修改\src\main\java\io\ken\springcloud\eurekaserver\App.java 基于Spring Boot创建启动类，添加上 @EnableDiscoveryClient 注解
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。
package io.ken.springcloud.ribbonclient;
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;
@EnableDiscoveryClient
@SpringBootApplication
public class App {
public static void main(String[] args) {
SpringApplication.run(App.class, args);
}
@Bean
@LoadBalanced
public RestTemplate restTemplate() {
return new RestTemplate();
}
}
3、编写Eureka服务访问
创建TestService.java
TestService作为访问testservice的代理服务类，通过RestTemplate访问远程testservice，Ribbon会负责把servicename替换成实际要访问的host
package io.ken.springcloud.ribbonclient.service;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;
@Service
public class TestService {
@Autowired
private RestTemplate restTemplate;
public Object index() {
return restTemplate.getForObject("http://testservice", String.class);
}
public Object plus(int numA, int numB) {
String url = String.format("http://testservice/plus?numA=%s&numB=%s", numA, numB);
return restTemplate.getForObject(url, String.class);
}
}
4、编写服务入口
创建TestController
TestController作为访问服务testservice的入口
package io.ken.springcloud.ribbonclient.controller;
import io.ken.springcloud.ribbonclient.service.TestService;
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 TestController {
@Autowired
private TestService testService;
@RequestMapping("/")
public Object index() {
return "ribbon client";
}
@RequestMapping("/ti")
public Object ti() {
return testService.index();
}
@RequestMapping("/plus")
public Object plus(@RequestParam("numa") int numA, @RequestParam("numb") int numB) {
return testService.plus(numA, numB);
}
}
5、配置Eureka Client
在\src\main下创建文件夹resources文件夹并设置为Resources Root
在resources文件夹下创建application.yml文件并配置Eureka Client
server:
port: 8604
spring:
application:
name: ribbonclient
eureka:
client:
serviceUrl:
defaultZone: http://localhost:8800/eureka/
6、服务访问/消费测试
RibonClient项目启动后，访问 http://localhost:8604/ti 会交替显示以下内容
{
"code": 0,
"message": "hello",
"content": null,
"serviceName": "testservice",
"host": "localhost:8602"
}
{
"code": 0,
"message": "hello",
"content": null,
"serviceName": "testservice",
"host": "localhost:8603"
}
四、备注
本篇示例代码
https://github.com/ken-io/springcloud-course/tree/master/chapter-02
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