集成Ribbon的客户端调用工具——Feign

什么是Feign？

客户端调用工具

• Ribbon+RestTemplate
• Feign

Feign特性：

• Feign本身包含Ribbon
• Fegin是一个采用基于接口的注解的声明式客户端调用工具，更加简便

---

基于上个环境来做一些改造：

https://github.com/HCJ-shadow/Ribbon

创建msc-consumer-feign-80工程

pom依赖

主要是spring-cloud-starter-openfeign

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.1.7.RELEASE</version>
    <relativePath/> <!-- lookup parent from repository -->
</parent>

<properties>
    <java.version>1.8</java.version>
    <spring-cloud.version>Greenwich.SR2</spring-cloud.version>
</properties>

<dependencies>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>

    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-config</artifactId>
    </dependency>
    <!--        Eureka客户端启动需要依赖web模块-->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

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

</dependencies>

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-dependencies</artifactId>
            <version>${spring-cloud.version}</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
    </plugins>
</build>

定义service接口

package zkrun.top.service;

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;

@FeignClient("msc-provider")    //@FeignClient("服务名")
public interface FeignService {

    @RequestMapping(value = "/info/get")
    public String request();

}

定义Controller调用Service接口

package zkrun.top.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import zkrun.top.service.FeignService;

@RestController
public class FeignController {

    @Autowired
    FeignService feignService;

    @RequestMapping(value = "/feign/info/get")
    public String request()
    {
       return this.feignService.request();
    }

}

主启动类

package zkrun.top;

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

@SpringBootApplication
@EnableFeignClients
@EnableEurekaClient
public class App_Consumer_Feign_80
{
   public static void main(String[] args)
   {
      SpringApplication.run(App_Consumer_Feign_80.class, args);
   }
}

application.yaml

server:
  port: 80

eureka:
  client:
    service-url:
      defaultZone: http://eureka6001.com:6001/eureka/,http://eureka6002.com:6002/eureka/,http://eureka6003.com:6003/eureka/

spring:
  application:
    name: feign-consumer

运行测试

集成了轮询效果。

---

小结：

• Feign的调用逻辑，访问Controller定义的路径，调用feignService.request()方法，而service接口层中定义了服务名和服务请求路径，最后通过服务名和请求路径实现对服务提供者的调用。
• Feign的接口在实际开发中经常抽取出一个单独模块，以便复用。

代码参考：https://github.com/Noneplus/JavaDev-Note/tree/master/SpringCloud代码