Feign的基本使用

我使用的SpringCloud版本为Hoxton.SR3

服务消费方使用

第一步：引入Feign依赖　　

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

第二步：启用Feign，在启动类添加开启的注解

package com.company;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.SpringCloudApplication;
import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.netflix.ribbon.RibbonClient;
import org.springframework.cloud.openfeign.EnableFeignClients;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

//@EnableDiscoveryClient //启用Eureka客户端
//@SpringBootApplication
//@EnableCircuitBreaker //启用Hystrix熔断功能
@SpringCloudApplication //替代以上三个注解
@EnableFeignClients //启用Feign
public class ConsumerApplication {

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

    //启用Feign以后无需再注入
//    @Bean
//    @LoadBalanced
//    public RestTemplate restTemplate(){
//        return new RestTemplate();
//    }
}

第三步：写一个Feign的客户端

package com.company.client;

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

@FeignClient("user-service")//声明这是一个Feign的客户端接口，value指明服务id
public interface UserFeignClient {
    //使用SpringMVC的注解指明请求方式、请求路径、请求参数和响应类型
    @GetMapping("/user/{id}")
    public String getUserById(@PathVariable(name = "id") Long id);
}

第四步：改造消费方的调用方式

package com.company.controller;

import com.company.client.UserFeignClient;
import com.netflix.hystrix.contrib.javanica.annotation.DefaultProperties;
import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.client.discovery.DiscoveryClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

@RestController
@RequestMapping("/consumer3")//Feign
@Slf4j
@DefaultProperties(defaultFallback = "getUserByIdFallBack")
public class ConsumerController3 {

    @Autowired
    private UserFeignClient feignClient;

    @GetMapping("/{id}")
    @HystrixCommand
    public String getUserById(@PathVariable("id")Long id){
        long start=System.currentTimeMillis();
        String user = feignClient.getUserById(id);
        long end=System.currentTimeMillis();
        log.debug("调用时长：{}",end-start);
        return user;
    }

    public String getUserByIdFallBack(){
        return "很抱歉，服务器3正忙，请稍后再试。";
    }

}

熔断依旧可用。

Feign内部已经使用了Ribbon的负载均衡