一、概述

1.OpenFeign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

GitHub：https://github.com/spring-cloud/spring-cloud-openfeign

官网解释：
https://cloud.spring.io/spring-cloud-static/Hoxton.SR1/reference/htmlsingle/#spring-cloud-openfeign

Feign是一个声明式WebService客户端。使用Feign能让编写Web Service客户端更加简单。
它的使用方法是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。Spring Cloud对Feign进行了封装，使其支持了Spring MVC标准注解和HttpMessageConverters。Feign可以与Eureka和Ribbon组合使用以支持负载均衡

2.能干嘛

Feign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，往往一个接口会被多处调用，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接口上面标注Mapper注解,现在是一个微服务接口上面标注一个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Spring cloud 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口且以声明式的方法，优雅而简单的实现了服务调用

3.Feign和OpenFeign两者区别

Feign	OpenFeign
Feign是Spring Cloud组件中的一个轻量级RESTful的HTTP服务客户端 Feign内置了Ribbon，用来做客户端负载均衡，去调用服务注册中心的服务。Feign的使用方式是：使用Feign的注解定义接口，调用这个接口，就可以调用服务注册中心的服务	OpenFeign是Spring Cloud 在Feign的基础上支持了SpringMVC的注解，如@RequesMapping等等。OpenFeign的@FeignClient可以解析SpringMVC的@RequestMapping注解下的接口，并通过动态代理的方式产生实现类，实现类中做负载均衡并调用其他服务。
```xml

org.springframework.cloud spring-cloud-starter-feign

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

二、OpenFeign使用步骤

1.接口增加注解@FeignClient

2.新建cloud-consumer-feign-order80

2.1 Feign在消费端使用

3.POM

<?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>mscloud03</artifactId>
        <groupId>com.atguigu.springcloud</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

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

    <dependencies>
        <!--openfeign-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>
        <!--eureka client-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <!-- 引入自己定义的api通用包，可以使用Payment支付Entity -->
        <dependency>
            <groupId>com.atguigu.springcloud</groupId>
            <artifactId>cloud-api-commons</artifactId>
            <version>${project.version}</version>
        </dependency>
        <!--web-->
        <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>
        <!--一般基础通用配置-->
        <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>

4.YAML

server:
  port: 80

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

5.启动类(增加@EnableFeignClients)

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);
    }
}

6.业务类

6.1 业务逻辑接口增加@FeignClient配置调用provider服务

6.2 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 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}")
    CommonResult<Payment> getPaymentById(@PathVariable("id") Long id);
}

6.3 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.总结

三、OpenFeign超时控制
1.超时设置，故意设置超时演示出错情况
1.1 服务提供方8001故意写暂停程序
```java package com.atguigu.springcloud.controller;

import com.atguigu.springcloud.entities.CommonResult; import com.atguigu.springcloud.entities.Payment; import com.atguigu.springcloud.service.PaymentService; import lombok.extern.slf4j.Slf4j; 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 javax.annotation.Resource; import java.util.List; import java.util.concurrent.TimeUnit;

@RestController @Slf4j public class PaymentController { @Value(“${server.port}”) private String serverPort;

@Resource
private PaymentService paymentService;

@Resource
private DiscoveryClient discoveryClient;

@PostMapping(value = "/payment/create")
public CommonResult create(@RequestBody Payment payment)
{
    int result = paymentService.create(payment);
    log.info("*****插入操作返回结果:" + result);

    if(result > 0)
    {
        return new CommonResult(200,"插入成功,返回结果"+result+"\t 服务端口："+serverPort,payment);
    }else{
        return new CommonResult(444,"插入失败",null);
    }
}

@GetMapping(value = "/payment/get/{id}")
public CommonResult<Payment> getPaymentById(@PathVariable("id") Long id)
{
    Payment payment = paymentService.getPaymentById(id);
    log.info("*****查询结果:{}",payment);
    if (payment != null) {
        return new CommonResult(200,"查询成功"+"\t 服务端口："+serverPort,payment);
    }else{
        return new CommonResult(444,"没有对应记录,查询ID: "+id,null);
    }
}

@GetMapping(value = "/payment/discovery")
public Object discovery()
{
    List<String> services = discoveryClient.getServices();
    for (String element : services) {
        System.out.println(element);
    }

    List<ServiceInstance> instances = discoveryClient.getInstances("CLOUD-PAYMENT-SERVICE");
    for (ServiceInstance element : instances) {
        System.out.println(element.getServiceId() + "\t" + element.getHost() + "\t" + element.getPort() + "\t"
                + element.getUri());
    }
    return this.discoveryClient;
}

@GetMapping(value = "/payment/lb")
public String getPaymentLB()
{
    System.out.println("*****lb from port: "+serverPort);
    return serverPort;
}

@GetMapping(value = "/payment/feign/timeout")
public String paymentFeignTimeOut()
{
    System.out.println("*****paymentFeignTimeOut from port: "+serverPort);
    //暂停几秒钟线程
    try { TimeUnit.SECONDS.sleep(3); } catch (InterruptedException e) { e.printStackTrace(); }
    return serverPort;
}

}

<a name="XwTJE"></a>
### 1.2 服务消费方80添加超时方法PaymentFeignService
```java

package com.atguigu.springcloud.service;

import com.atguigu.springcloud.entities.CommonResult;
import com.atguigu.springcloud.entities.Payment;
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}")
    CommonResult<Payment> getPaymentById(@PathVariable("id") Long id);

    @GetMapping(value = "/payment/feign/timeout")
    String paymentFeignTimeOut();
}

1.3 服务消费方80添加超时方法OrderFeignController


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);
    }

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

1.4 测试

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

错误页面

2.OpenFeign默认等待1秒钟，超过后报错

3.OpenFeign是什么?

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。

OpenFeign默认支持Ribbon

4.YML文件里需要开启OpenFeign客户端超时控制

server:
  port: 80

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

#设置feign客户端超时时间(OpenFeign默认支持ribbon)
ribbon:
#指的是建立连接所用的时间，适用于网络状况正常的情况下,两端连接所用的时间
  ReadTimeout: 5000
#指的是建立连接后从服务器读取到可用资源所用的时间
  ConnectTimeout: 5000

四、OpenFeign日志打印功能

1. 是什么？

Feign 提供了日志打印功能，我们可以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接口的调用情况进行监控和输出

2. 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。

3. 配置日志bean


package com.atguigu.springcloud.cfgbeans;

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


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

4. 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/

#设置feign客户端超时时间
#springCloud默认开启支持ribbon
ribbon:
#指的是建立连接所用的时间，适用于网络状况正常的情况下,两端连接所用的时间
  ReadTimeout: 5000
#指的是建立连接后从服务器读取到可用资源所用的时间
  ConnectTimeout: 5000

logging:
  level:
    # feign日志以什么级别监控哪个接口
    com.atguigu.springcloud.service.PaymentFeignService: debug

SpringCloud

(四) OpenFegin服务接口调用