Feign

集成工具

• 远程调用：声明式客户端
• ribbon 负载均衡和重试
• hystrix 降级和熔断

feign 声明式客户端接口

微服务应用中，ribbon 和 hystrix 总是同时出现，feign 整合了两者，并提供了声明式消费者客户端

• 用 feign 代替 hystrix+ribbon
  
  只需要声明一个抽象接口，就可以通过接口做远程调用，不需要再使用 RestTemplate 来调用

// 调用远程的商品服务，获取订单的商品列表
// 通过注解，配置：
// 1. 调用哪个服务
// 2. 调用服务的哪个路径
// 3. 向路径提交什么参数数据
@FeignClient(name="item-service")//item-service指在eureka中注册的服务名
public interface ItemClient {
    @GetMapping("/{orderId}")
    JsonResult<List<Item>> getItems(@PathVariable String orderId);//@PathVariable在这里是指向接口传递的参数
}

在这里使用 @GetMapping("/{orderId}")， 指定的是向远程服务调用的路径

Demo

1.新建springboot模块，添加依赖

2.application.yml配置

# 应用名称
spring:
  application:
    name: feign

# Actuator Web 访问端口
server:
  port: 3001
eureka:
  client:
    service-url:
      defaultZone: http://eureka1:2001/eureka,http://eureka2:2002/eureka

1）测试远程调用（声明式客户端接口）
1.启动类添加Feign注解

@EnableFeignClients

2.新建Feign包，创建ItemFeignService接口

import cn.tedu.sp01.pojo.Item;
import cn.tedu.sp01.util.JsonResult;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;

import java.util.List;

//根据服务id，从注册表得到主机地址
@FeignClient(name = "item-service")
public interface ItemFeignService {
    @GetMapping("/{orderId}")
    JsonResult<List<Item>> getItems(@PathVariable(value = "orderId") String orderId);

    @PostMapping("/decreaseNumber")
    JsonResult<?> decreaseNumber(@RequestBody List<Item> items);

}

创建UserFeignService接口

import cn.tedu.sp01.pojo.User;
import cn.tedu.sp01.util.JsonResult;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestParam;

@FeignClient(name= "user-service")
public interface UserFeignService {
    @GetMapping("/{userId}")
    JsonResult<User> getUser(@PathVariable(value = "userId") Integer userId);


    @GetMapping(value = "/{userId}/score")
    JsonResult<?> addScore(@PathVariable(value = "userId") Integer userId,
                           @RequestParam(value = "score") Integer score);//@RequestParam在Controller中可以省略，此处不能省略
}

创建OrderFeignService接口

import cn.tedu.sp01.pojo.Order;
import cn.tedu.sp01.util.JsonResult;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;

@FeignClient("order-service")
public interface OrderFeignService {
    @GetMapping("/{orderId}")
    JsonResult<Order> getOrder(@PathVariable(value = "orderId") String orderId);

    @GetMapping("/")
    JsonResult<?> addOrder();
}

3.创建controller

import cn.tedu.sp01.pojo.Item;
import cn.tedu.sp01.pojo.Order;
import cn.tedu.sp01.pojo.User;
import cn.tedu.sp01.util.JsonResult;
import cn.tedu.sp09.feign.ItemFeignService;
import cn.tedu.sp09.feign.OrderFeignService;
import cn.tedu.sp09.feign.UserFeignService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@Slf4j
public class ItemController {
    @Autowired
    private ItemFeignService itemFeignService;

    @Autowired
    private UserFeignService userFeignService;

    @Autowired
    private OrderFeignService orderFeignService;

    @GetMapping("/item-service/{orderId}")
    public JsonResult<List<Item>> getItems(@PathVariable String orderId){
        return itemFeignService.getItems(orderId);
    }
    @PostMapping("/item-service/descrease")
    public JsonResult<?> decreaseNumber(@RequestBody List<Item> items){
        return itemFeignService.decreaseNumber(items);
    }
    @GetMapping("/user-service/{userId}")
    public JsonResult<User> getUser(@PathVariable Integer userId){
        return userFeignService.getUser(userId);
    }
    @GetMapping("/user-service/{userId}/score")
    public JsonResult<?> addScore(@PathVariable Integer userId,
                                  Integer score){
        return userFeignService.addScore(userId, score);
    }
    @GetMapping("/order-service/{orderId}")
    public JsonResult<Order> getOrder(@PathVariable String orderId){
        return orderFeignService.getOrder(orderId);
    }
    @GetMapping("/order-service/")
    public JsonResult<?> addOrder(){
        return orderFeignService.addOrder();
    }
}

测试：

远程调用成功！！！

调用流程：

feign + ribbon 负载均衡和重试

无需额外配置，feign 默认已启用了 ribbon 负载均衡和重试机制。可以通过配置对参数进行调整
重试的默认配置参数:

ConnectTimeout=1000
ReadTimeout=1000
MaxAutoRetries=0
MaxAutoRetriesNextServer=1

转载自CSDN-专业IT技术社区

原文链接：https://blog.csdn.net/qq_45273552/article/details/112761439