OpenFeign 服务接口调用

一、概述

1、是什么

Feign 是一个声明式的web服务客户端，让编写web服务客户端变得非常容易，只需创建一个接口并在接口上添加注解即可。

2、能干什么

Feign 旨在使编写 Java Http 客户端变得更容易。

前面在使用 Ribbon+RestTemplate 时，利用 RestTemplate 对 http 请求的封装处理，形成了一套模版化的调用方法。但是在实际开发中，由于对服务依赖的调用可能不止一处，往往一个接囗会被多处调用，所以通常都会针对每个微服务自行封装一些客户端类来包装这些依赖服务的调用。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，我们只需创建一个接口并使用注解的方式来配置它（以前是Dao接囗上面标注Mapper注解，现在是一个微服务接囗上面标汪一个@Feign注解即可)，即可完成对服务提供方的接口绑定，简化了使用Springcloud Ribbon 时，自动封装服务调用客户端的开发量。

Feign 集成了 Ribbon

利用Ribbon维护了Payment的服务列表信息，并且通过轮询实现了客户端的负载均衡。而与Ribbon不同的是，通过feign只需要定义服务绑定接囗且以声明式的方法，优雅而简单的实现了服务调用

3、Feign和OpenFeign两者区别

二、OpenFeign使用步骤

1）新建cloud-consumer-feign-order80，Feign在消费端使用

2）改POM文件

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>cloud2020</artifactId>
        <groupId>com.atguigu.springcloud</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>cloud-consumer-feign-order80</artifactId>


    <!--openfeign-->
    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <dependency>
            <groupId>com.atguigu.springcloud</groupId>
            <artifactId>cloud-api-common</artifactId>
            <version>${project.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
</project>

3）改YML文件

server:
  port: 80
eureka:
  client:
    register-with-eureka: false
    service-url:
      defaultZone: http://eureka7001.com:7001/eureka, http://eureka7002.com:7002/eureka
 

4）启动类

package com.atguigu.springcloud;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.openfeign.EnableFeignClients;

@SpringBootApplication
@EnableFeignClients
public class OrderFeignMain80 {
    public static void main(String[] args) {
        SpringApplication.run(OrderFeignMain80.class,args);
    }
}

5）业务逻辑接口+@FeignClient配置调用provider服务

新建PaymentFeignService接口并新增注解@FeignClient

package com.atguigu.springcloud.service;

import com.atguigu.springcloud.entities.CommonResult;
import com.atguigu.springcloud.entities.Payment;
import feign.Param;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;

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

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

6）控制层Controller

package com.atguigu.springcloud.controller;

import com.atguigu.springcloud.entities.CommonResult;
import com.atguigu.springcloud.entities.Payment;
import com.atguigu.springcloud.service.PaymentFeignService;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

import javax.annotation.Resource;

@RestController
public class OrderFeignController {

    @Resource
    private PaymentFeignService paymentFeignService;

    @GetMapping(value = "/consumer/payment/get/{id}")
    public CommonResult<Payment> getPaymentById(@PathVariable("id") Long id){
       return paymentFeignService.getPaymentById(id);
    }
}

7）测试

• 先启动2个eureka集群7001/7002
• 再启动2个微服务8001/8002
• 启动OpenFeign启动
• http://localhost/consumer/payment/get/31
• Feign自带负载均衡配置项

8）小总结

三、OpenFeign超时控制

超时设置，故意设置超时演示出错情况

服务提供方8001故意写暂停程序

@GetMapping(value = "/payment/feign/timeout")
public String paymentFeignTimeout() {
    try {
        TimeUnit.SECONDS.sleep(3);
    } catch (Exception e) {
        e.printStackTrace();
    }
    return "8002";
}

服务消费方80添加超时方法PaymentFeignService

@GetMapping(value = "/payment/feign/timeout")
public String paymentFeignTimeout();

服务消费方80添加超时方法OrderFeignController

@GetMapping(value = "/consumer/payment/feign/timeout")
public String paymentFeignTimeout(){
   return paymentFeignService.paymentFeignTimeout();
}

测试：http://localhost/consumer/payment/feign/timeout

OpenFeign默认等待一秒钟，超过后报错

默认Feign客户端只等待一秒钟，但是服务端处理需要超过1秒钟，导致Feign客户端不想等待了，直接返回报错。为了避免这样的情况，有时候我们需要设置Feign客户端的超时控制。

yml文件中开启配置

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

四、OpenFeign日志打印功能

Feign提供了日志打印功能，我们可通过配置来调整日志级别，从而了解Feign中Http请求的细节。说白了就是对Feign接囗的调用情况进行监控和输出

日志级别

• NONE：默认的，不显示任何日志。
• BASIC：仅记录请求方法、URL、响应状态码及执行时间。
• HEADERS：除了BASIC中定义的信息之外，还有请求和响应的头信息。
• FULL：除了HEADERS中定义的信息之外，还有请求和响应的正文及元数据。

配置日志bean

package com.atguigu.springcloud.config;

import feign.Logger;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class FeignConfig {
    @Bean
    Logger.Level feignLoggerLevel() {
        return Logger.Level.FULL;
    }
}

YML文件里需要开启日志的Feign客户端

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:
    com.atguigu.springcloud.service.PaymentFeignService: debug