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OpenFeign 简介

OpenFeign 提供了一种声明式的远程调用接口。

OpenFeign 能做什么

目的是为了简易HTTP客户端的编写。

之前在 笔记中介绍了 Ribbon + RestTemplate 的使用。Ribbon + RestTemplate 是多http请求做了封装处理，形成了模版化的调用。但是在实际的开发中，由于对服务依赖的调用可能不止一处，往往一个接口被多处调用，所以需要对每个微服务进行封装。鉴于此 Feign 在此基础上为我们提供了封装操作，由Feign 帮我门定义和实现依赖服务接口的定义。因此简化了我们的操作，只需要创建一个接口并使用注解的形式来配置它（比如Mapper接口上标注@Mapper注解，现在是在一个微服务接口上标注一个@FeignClient注解），就可以完成对服务接口的绑定，简化了Spring cloud Ribbon使用时候封装客户端的开发量

如何使用

Declarative REST Client: Feign creates a dynamic implementation of an interface decorated with JAX-RS or Spring MVC annotations

在主启动类上通过注解 @EnableFeignClients、 接口上通过注解 @FeignClient 实现

@SpringBootApplication
@EnableFeignClients
public class WebApplication {

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

    @FeignClient("name")
    static interface NameService {
        @RequestMapping("/")
        public String getName();
    }
}

OpenFeign 使用Example

• eureka服务集群 127.0.0.1:7001 127.0.0.1:7002
• 微服务 – 消费者服务 consumner-order， 服务注册 eureka
• 微服务 – 支付服务 payment8001, payment8002, 服务注册进eureka。服务名叫 CLOUD-PAYMENT-SERVICE

1、新建子模块 consumner-order

依赖pom.xml

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

2、配置文件application.yaml’

server:
  port: 80

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

3、主启动类

@EnableFeignClients 开启 Feign 客户端

@SpringBootApplication
@EnableFeignClients
public class FeignMain80 {

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

}

4、接口层 service/PaymentFeignService.java

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

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

}

5、业务控制器 controller/OrderController.java

@RestController
public class OrderController {

    @Resource
    private PaymentFeignService paymentFeignService;

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

}

6、启动eureka7001、eureka7002、payment8001、payment8002、consumer-order

访问 127.0.0.1:80//consumer/payment/get/4

# 第一次

{"code":200,"message":"查询成功, serverPort: 8001","data":{"id":4,"serial":"jeffcail00004"}}

# 第二次

{"code":200,"message":"查询成功, serverPort: 8002","data":{"id":4,"serial":"jeffcail00004"}}

# 第三次

{"code":200,"message":"查询成功, serverPort: 8001","data":{"id":4,"serial":"jeffcail00004"}}

# 第四次

{"code":200,"message":"查询成功, serverPort: 8002","data":{"id":4,"serial":"jeffcail00004"}}

OpenFeign 超时控制 （OpenFeign默认超时时间为1秒）

在payment8001、payment8002中新增接口

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

在order 服务中新增调用接口

service/PaymentFeignService.jva

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

业务控制器 controller/OrderController.java

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

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

超时错误

Whitelabel Error Page
This application has no explicit mapping for /error, so you are seeing this as a fallback.

Thu Jun 22 13:39:17 CST 2023
There was an unexpected error (type=Internal Server Error, status=500).
Read timed out executing GET http://CLOUD-PAYMENT-SERVICE/payment/feign/timeout

YAML文件中开启超时配置

# 设置feigin 客户端超时时间（OpenFeign默认支持ribbon）
ribbon:
  # 读超时时间 5秒
  ReadTimeout: 5000
  # 建立连接 超时时间 5秒
  ConnectTimeout: 5000

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

等待3秒后

8001