Feign学习笔记

什么是Feign

Feign是一个声明式WebService客户端，使用Feign能让编写WebService客户端变得简单。

使用方法

定义一个服务接口然后在上面添加注解。Feign也支持可拔插式的编码器和解码器。SpringCloud对Feign进行啦封装，使其支持SpringMVC标准注解和HttpMessageConverters。Feign可以与eureka和Ribbon组合使用支持负载均衡。

实际应用

在实际开发应用中，由于对服务的依赖调用不止一处，往往一个接口会被多出调用，所以通常都会争对每一个微服务自行封装来包装这些依赖的调用。所以Feign在此基础上做了进一步封装由他来帮助我们定义和实现依赖服务接口的定义。在Feign的实现下，我们只需要创建一个接口并使用注解方式来配置。即可完成对服务提供方的接口绑定，简化了SpringCloud Ribbon时，自动化封装了客户端的并发量。

代码实现

目录结构

8001服务提供接口

package ink.awz.springcloud.controller;

import ink.awz.springcloud.entity.JsonResult;
import ink.awz.springcloud.entity.Payment;
import ink.awz.springcloud.service.PaymentService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.discovery.DiscoveryClient;
import org.springframework.web.bind.annotation.*;

import java.util.List;
import java.util.concurrent.TimeUnit;


/**
 * @author 杨杰
 * @version 1.0
 * @date 2022/7/17 20:17
 */
@RestController
@Slf4j
public class PaymentController {

    @Autowired
    private PaymentService paymentService;

    @Value("${server.port}")
    private String serverPort;

    @Autowired
    private DiscoveryClient discoveryClient;

    @PostMapping(value = "/payment/create")
    public JsonResult create(@RequestBody Payment payment) {

        int resultNumber = paymentService.create(payment);

        if (resultNumber > 0) {
            return new JsonResult("200","插入成功,port"+serverPort);
        } else {
            return new JsonResult("444","插入失败,port"+serverPort);
        }

    }

    @GetMapping(value = "/payment/get/{id}")
    public JsonResult getPaymentById(@PathVariable Long id) {
        return new JsonResult(paymentService.getPaymentById(id),"200","查询成功,port"+serverPort);
    }


    @GetMapping("/payment/discovery")
    public Object discovery() {

        List<String> services = discoveryClient.getServices();
        for (String element : services) {
            log.info("****element"+element);
        }

        List<ServiceInstance> instances = discoveryClient.getInstances("CLOUD-PAYMENT-SERVICE");
        for (ServiceInstance instance : instances) {
            log.info(instance.getServiceId()+"\t"+instance.getPort()+"\t"+instance.getHost()+"\t"+instance.getUri());
        }

        return this.discoveryClient;
    }


   

}

Feign客户端

@Component
@FeignClient(value = "CLOUD-PAYMENT-SERVICE")
public interface PaymentFeignService {

    @GetMapping(value = "/payment/get/{id}")
    public JsonResult getPaymentById(@PathVariable("id") Long id) ;

}

说明@FeignClient(value = “CLOUD-PAYMENT-SERVICE”)

绑定CLOUD-PAYMENT-SERVICE服务

@GetMapping(value = "/payment/get/{id}")
    public JsonResult getPaymentById(@PathVariable("id") Long id)

绑定具体对应提供方接口
CLOUD-PAYMENT-SERVICE 服务名称

Feign客户端Controller层调用

@RestController
@Slf4j
public class OrderFeignController {

    @Autowired
    private PaymentFeignService paymentFeignService;

    @GetMapping(value = "/consumer/payment/get/{id}")
    public JsonResult getPaymentById(@PathVariable("id") Long id) {
        return new JsonResult<>(paymentFeignService.getPaymentById(id),"200","数据查询成功");
    }

}

Feign超时控制

在实际业务中有可能提供方做复杂查询，需要花费几秒钟时间，而Feign客户端默认连接提供方的时间为1秒，否则就会抛出异常。可以通过配置文件设置连接时间

server:
  port: 80

eureka:
  client:
    register-with-eureka: false
    service-url:
      defaultZone: http://eureka7001.com:7001/eureka,http://eureka7002.com:7002/eureka

ribbon:
  ReadTimeout: 5000
  ConnectTimeout: 5000

logging:
  level:
    ink.awz.springcloud.service.PaymentFeignService: debug

为什么是Ribbon，因为Feign底层使用啦Ribbon做负载均衡，可以通过配置Ribbon连接时间来控制Feign的连接时间。