SpringCloud - Feign

package com.imooc.product.controller;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class ServerController {

    @GetMapping("/msg")
    public String msg() {
        return "this is product' msg";
    }
}

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

package com.imooc.order;

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;

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class OrderApplication {

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

package com.imooc.order.client;

import com.imooc.order.dataobject.ProductInfo;
import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import java.util.List;

@FeignClient(name = "product")
public interface ProductClient {

    @GetMapping("/msg")
    String productMsg();

    @PostMapping("/product/listForOrder")
    List<ProductInfo> listForOrder(@RequestBody List<String> productIdList);
}

package com.imooc.order.controller;

import com.imooc.order.client.ProductClient;
import com.imooc.order.dataobject.ProductInfo;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import java.util.Arrays;
import java.util.List;

@RestController
@Slf4j
public class ClientController {

    @Autowired
    private ProductClient productClient;

    @GetMapping("/getProductMsg")
    public String getProductMsg() {
        String response = productClient.productMsg();
        log.info("response={}", response);
        return response;
    }

    @GetMapping("/getProductList")
    public String getProductList() {
        List<ProductInfo> productInfoList = productClient.listForOrder(Arrays.asList("164103465734242707"));
        log.info("response={}", productInfoList);
        return "ok";
    }
}

Feign用来进行应用之间的通信，在order项目中调用商品服务，应用feign

1. 用的时候需要在pom.xml添加feign依赖。
2. 在启动主类(OrderApplication)上加注解@EnableFeignClients。
3. 在客户端定义好要调用的服务和接口(ProductClient)，这里是要调用商品服务的商品详情接口productMsg()，主要是通过@FeignClient匹配服务@GetMapping匹配方法的。
4. 在客户端添加ClientController类，依赖注入ProductClient，调用ProductClient的getProductMsg()。

• Feign 主要是 feign client + ribbon，feign其实就通过@FeignClient注解的接口的serviceName+ribbon拿到目标服务ip和port，然后根据@FeignClient注解的接口的某个方法上的requestMapping注解，组装成完整的请求url，然后利用restTemplate去请求目标url。