Feign是一个声明式的伪Http客户端，它使得写Http客户端变得更简单。使用Feign，只需要创建一个接口并注解。它具有可插拔的注解特性，可使用Feign 注解和JAX-RS注解。Feign支持可插拔的编码器和解码器。Feign默认集成了Ribbon，并和Eureka结合，默认实现了负载均衡的效果。

新建项目 引入 pom依赖

        <!--Eureka服务-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
            <version>2.1.1.RELEASE</version>
        </dependency>
        <!--feign依赖-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>

yml文件3步走

#1.先给这个服务起一个名字
spring:
  application:
    name: service-feign
#2.给定一个指定的端口号
server:
  port: 8765
#ssss  注册中心地址:
eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka/eureka

package com.tg.feign_demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.openfeign.EnableFeignClients;

@SpringBootApplication
@EnableEurekaClient//激活eureka客户端
@EnableFeignClients//激活Feign
public class FeignDemoApplication {

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

package com.tg.feign_demo;

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;


//FeignClient  直接定义该当前接口对应的注册中心 的服务名 用于指定调用哪一个服务
@FeignClient(value = "EUREKA-CLIENT")
public interface RestHiService {

    //对应的服务中心的服务方法
    @GetMapping(value = "/hi")
    public String sayHi();
}
package com.tg.feign_demo;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

@org.springframework.web.bind.annotation.RestController
public class RestController {

    @Autowired
    RestHiService restHiService;

    @RequestMapping(value = "/hi", method = RequestMethod.GET)
    public String sayHi() {
        return restHiService.sayHi();
    }
}

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