Feign的基本使用

我使用的SpringCloud版本為Hoxton.SR3

服務消費方使用

第一步：引入Feign依賴　　

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

第二步：啟用Feign，在啟動類添加開啟的注解

 

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 //啟用Eureka客戶端
//@SpringBootApplication
//@EnableCircuitBreaker //啟用Hystrix熔斷功能
@SpringCloudApplication //替代以上三個注解
@EnableFeignClients //啟用Feign
public class ConsumerApplication {

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

    //啟用Feign以后無需再注入
//    @Bean
//    @LoadBalanced
//    public RestTemplate restTemplate(){
//        return new RestTemplate();
//    }
}

第三步：寫一個Feign的客戶端

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")//聲明這是一個Feign的客戶端接口，value指明服務id
public interface UserFeignClient {
    //使用SpringMVC的注解指明請求方式、請求路徑、請求參數和響應類型
    @GetMapping("/user/{id}")
    public String getUserById(@PathVariable(name = "id") Long id);
}

 

第四步：改造消費方的調用方式

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("調用時長：{}",end-start);
        return user;
    }

    public String getUserByIdFallBack(){
        return "很抱歉，服務器3正忙，請稍后再試。";
    }

}

熔斷依舊可用。

Feign內部已經使用了Ribbon的負載均衡