Spring Cloud Feign快速入门案例

一 新建一个Spring boot基础工程，取名feign-consumer，在pom.xml中增加相关依赖

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

    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-eureka</artifactId>
    </dependency>

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

二 创建应用主类，并通过@EnableFeignClients注解开启Spring Cloud Feign的支持功能

package com.didispace;

import feign.Logger;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.netflix.feign.EnableFeignClients;
import org.springframework.context.annotation.Bean;

@EnableFeignClients
@EnableDiscoveryClient
@SpringBootApplication
public class ConsumerApplication {
    public static void main(String[] args) {
        SpringApplication.run(ConsumerApplication.class, args);
    }

}

三 定义HelloService接口，通过@FeignClient指定服务名类绑定服务

package com.didispace.web;

import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.web.bind.annotation.*;

@FeignClient(name="HELLO-SERVICE", fallback = HelloServiceFallback.class)
public interface HelloService {

    //绑定具体服务的REST接口
    @RequestMapping("/hello")
    String hello();
}

四 创建ConsumerController来实现对Feign客户端的调用

package com.didispace.web;

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

@RestController
public class ConsumerController {
    //使用@Autowired直接注入上面定义的HelloService的实例
    @Autowired
    HelloService helloService;

    @RequestMapping(value = "/feign-consumer", method = RequestMethod.GET)
    public String helloConsumer() {
        //调用了绑定HELLO-SERVICE服务接口的客户端向服务发起/hello接口的调用
        return helloService.hello();
    }
}

五 新增配置文件

spring.application.name=feign-consumer
server.port=9001

eureka.client.serviceUrl.defaultZone=http://localhost:1111/eureka/

六 测试

1 启动Eureka，两个Hello-service，然后启动Feign-consumer。

2 观察Eureka面板

3 发送http://localhost:9001/feign-consumer

第一个Hello-service的控制台打印：

2018-08-15 19:42:53.550  INFO 8028 --- [nio-8082-exec-1] com.didispace.web.HelloController        : /hello, host:DESKTOP-5SDKDG4, service_id:hello-service

2018-08-15 19:43:24.924  INFO 8028 --- [nio-8082-exec-3] com.didispace.web.HelloController        : /hello, host:DESKTOP-5SDKDG4, service_id:hello-service

第二个Hello-service的控制台打印：

2018-08-15 19:43:08.548  INFO 12088 --- [nio-8081-exec-3] com.didispace.web.HelloController        : /hello, host:DESKTOP-5SDKDG4, service_id:hello-service

2018-08-15 19:43:14.169  INFO 12088 --- [nio-8081-exec-5] com.didispace.web.HelloController        : /hello, host:DESKTOP-5SDKDG4, service_id:hello-service

实现了客户端的负载均衡。