springCloud之集成Feign

Feign是什么？

• Feign是Netflix开发的一款声明式服务调用组件
• Feign可以帮助我们更快捷、优雅地调用HTTP API。
• Feign 是 Spring Cloud Netflix 模块的子模块，它是 Spring Cloud 对 Netflix Feign 的二次封装，主要负责 Spring Cloud 的服务调用功能。

SpringCloud 集成Feign

1. 搭建Eureka Client : springCloud之Eureka搭建 - 楼上有只喵 (pyr9.github.io)

2. 引入依赖

   implementation 'org.springframework.cloud:spring-cloud-starter-openfeign'

3. 修改application.properties

   server.port=8085
   spring.application.name: micro-weather-eureka-client-feign
   eureka.client.serviceUrl.defaultZone: http://localhost:8761//eureka/
   # 连接的超时时间
   feign.client.config.feignName.connectTimeout: 5000
   # 读数据的超时时间
   feign.client.config.feignName.readTimeout: 5000

4. 创建一个接口，用FeignClient注解，指明需要调用的服务名和rest接口

   @FeignClient("micro-weather-city-eureka")
   public interface CityClient {
     @RequestMapping("/cities")
     String listCity();
   }

5. 修改启动类

      package com.pyr.spring.cloud.weather;
      
      import org.springframework.boot.SpringApplication;
      import org.springframework.boot.autoconfigure.SpringBootApplication;
      import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
      import org.springframework.cloud.openfeign.EnableFeignClients;
      
      @SpringBootApplication
      @EnableDiscoveryClient
      @EnableFeignClients
      public class Application {
      
        public static void main(String[] args) {
          SpringApplication.run(Application.class, args);
        }
      }
      
   
   6. 创建一个RestClientController来实现对Feign客户端的调用
   
      ```java
      package com.pyr.spring.cloud.weather.controller;
      
      import com.pyr.spring.cloud.weather.service.CityClient;
      import org.springframework.beans.factory.annotation.Autowired;
      import org.springframework.web.bind.annotation.RequestMapping;
      import org.springframework.web.bind.annotation.RestController;
      
      @RestController
      public class CityController {
        @Autowired
        private CityClient cityClient;
      
        @RequestMapping("/cities")
        public String listCity(){
          return cityClient.listCity();
        }
      }

6. 查看euraka服务端，可以看到该客户端注册成功，访问[localhost:8085/cities，可以获取到指定服务接口的返回