<span>SpringCloud系列之使用Feign进行服务调用</span>

在上一章的学习中，我们知道了微服务的基本概念，知道怎么基于Ribbon+restTemplate的方式实现服务调用，接着上篇博客，我们学习怎么基于Feign实现服务调用，请先学习上篇博客，然后再学习本篇博客

Feign是一个声明式的web service客户端，它使得编写web service客户端更为容易。创建接口，为接口添加注解，即可使用Feign。Feign可以使用Feign注解或者JAX-RS注解，还支持热插拔的编码器和解码器。

环境准备：

JDK 1.8
SpringBoot2.2.3
SpringCloud(Hoxton.SR6)
Maven 3.2+
开发工具
- IntelliJ IDEA
- smartGit

创建一个SpringBoot Initialize项目，详情可以参考我之前博客：SpringBoot系列之快速创建项目教程

  port: 8083
spring:
  application:
    name: feign-service-consumer
eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka/
    healthcheck:
      enabled: false
  instance:
    status-page-url-path: http://localhost:8761/actuator/info
    health-check-url-path: http://localhost:8761/actuator//health
    prefer-ip-address: true
    instance-id: feign-service-consumer8083

@FeignClient指定服务名称，@RequestMapping指定要调用的接口

package com.example.springcloud.client.service;

import com.example.springcloud.client.bean.User;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.stereotype.Service;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

/**
 * <pre>
 *  UserService
 * </pre>
 *
 * <pre>
 * @author mazq
 * 修改记录
 *    修改后版本:     修改人：  修改日期: 2020/07/28 13:09  修改内容:
 * </pre>
 */
@FeignClient(value = "EUREKA-SERVICE-PROVIDER")
@Service
public interface UserService {
    @RequestMapping(value = "/api/users/{username}",method = RequestMethod.GET)
    User findGithubUser(@PathVariable("username")String username);

}

加上@EnableEurekaClient，@EnableFeignClients，写个接口进行测试

package com.example.springcloud.client;

import com.example.springcloud.client.bean.User;
import com.example.springcloud.client.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.openfeign.EnableFeignClients;
import org.springframework.scheduling.annotation.Async;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
@EnableEurekaClient
@EnableFeignClients
@RestController
public class SpringcloudFeignClientApplication {

    @Autowired
    UserService userService;

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

    @GetMapping("/findUser/{username}")
    public User index(@PathVariable("username")String username){
        return userService.findGithubUser(username);
    }
}

要运行eureka服务端，eureka服务提供者，代码请参考上一章博客

补充：IDEA中多实例运行方法

step1：如图，不要加上勾选