前言

Feign的中文名称翻译过来是伪装
那么Feign伪装的是什么呢？答案很明确，Feign伪装的是服务提供者。
Feign可以用来做什么？既然能伪装，当然能提供服务提供者的功能，即RPC调用服务提供者功能。

一、构建Feign

step1
新建一个SpringBoot项目，导入web，feign，eureka client的pom依赖；这种依赖在各种IDE及SpringBoot构建网页上都是直接输入关键字按Enter就可以的

image.png

eureka:
  client:
    serviceUrl:
      defaultZone: http://server1:20001/eureka/
server:
  port: 8766
spring:
  application:
    name: service-feign

step3
配置负载均衡策略，新建一个类，配置bean Irule就可以了

import com.netflix.loadbalancer.IRule;
import com.netflix.loadbalancer.RandomRule;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class LoadBalancerConfig {
    @Bean
    public IRule getRule() {
        return new RandomRule();
    }
}

step4
主类开启Feign注解@EnableFeignClients，即允许开启Feign

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.openfeign.EnableFeignClients;
@EnableEurekaClient
@EnableFeignClients
@SpringBootApplication
public class FeignApplication {

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

step5
关键步骤来了，创建一个伪服务提供者接口（不需要实现），你伪装谁@FeignClient的value就写谁的名字。调用哪个接口就在RequestMapping 的value标注那个接口的url，方法名随便起，参数要给人间传过去

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;

@FeignClient(value = "service-hi")
public interface ServiceFeign {
    @RequestMapping(value = "/hi", method = RequestMethod.GET)
    String sayHi(@RequestParam(value = "name") String name);
}

step6
创建一个Controller便于前端观察

@RestController
public class FeignController {
    
    @Autowired
    private ServiceFeign serviceFeign;

    @GetMapping(value = "/hi")
    public String sayHi(@RequestParam String name) {
        return serviceFeign.sayHi(name);
    }
}

step7
启动eureka server，启动三个service-hi，启动service-feign，点击service-feign

image.png

image.png

总结

本篇git地址https://github.com/KouLouYiMaSi/springcloud