创建服务消费者（Feign）

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本节视频

• 【视频】微服务框架-SpringCloud-创建服务消费者（Feign）

概述

Feign 是一个声明式的伪 Http 客户端，它使得写 Http 客户端变得更简单。使用 Feign，只需要创建一个接口并注解。它具有可插拔的注解特性，可使用 Feign 注解和 JAX-RS 注解。Feign 支持可插拔的编码器和解码器。Feign 默认集成了 Ribbon，并和 Eureka 结合，默认实现了负载均衡的效果

• Feign 采用的是基于接口的注解
• Feign 整合了 ribbon

创建服务消费者

创建一个工程名为 hello-spring-cloud-web-admin-feign 的服务消费者项目，pom.xml 配置如下：

    4.0.0

    
        com.funtl
        hello-spring-cloud-dependencies
        1.0.0-SNAPSHOT
        ../hello-spring-cloud-dependencies/pom.xml
    

    hello-spring-cloud-web-admin-feign
    jar

    hello-spring-cloud-web-admin-feign
    http://www.funtl.com
    2018-Now

    
        
        
            org.springframework.boot
            spring-boot-starter-web
        
        
            org.springframework.boot
            spring-boot-starter-tomcat
        
        
            org.springframework.boot
            spring-boot-starter-thymeleaf
        
        
            org.springframework.boot
            spring-boot-starter-actuator
        
        
            org.springframework.boot
            spring-boot-starter-test
            test
        
        

        
        
            org.springframework.cloud
            spring-cloud-starter-netflix-eureka-server
        
        
            org.springframework.cloud
            spring-cloud-starter-openfeign
        
        

        
        
            net.sourceforge.nekohtml
            nekohtml
        
    

    
        
            
                org.springframework.boot
                spring-boot-maven-plugin
                
                    com.funtl.hello.spring.cloud.web.admin.feign.WebAdminFeignApplication
                
            
        
    

主要是增加了 Feign 的依赖

    org.springframework.cloud
    spring-cloud-starter-openfeign

Application

通过 @EnableFeignClients 注解开启 Feign 功能

package com.funtl.hello.spring.cloud.web.admin.feign;

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

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

application.yml

设置程序端口号为：8765

spring:
  application:
    name: hello-spring-cloud-web-admin-feign
  thymeleaf:
    cache: false
    mode: LEGACYHTML5
    encoding: UTF-8
    servlet:
      content-type: text/html

server:
  port: 8765

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/

创建 Feign 接口

通过 @FeignClient("服务名") 注解来指定调用哪个服务。代码如下：

package com.funtl.hello.spring.cloud.web.admin.feign.service;

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

@FeignClient(value = "hello-spring-cloud-service-admin")
public interface AdminService {

    @RequestMapping(value = "hi", method = RequestMethod.GET)
    public String sayHi(@RequestParam(value = "message") String message);
}

创建测试用的 Controller

package com.funtl.hello.spring.cloud.web.admin.feign.controller;

import com.funtl.hello.spring.cloud.web.admin.feign.service.AdminService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class AdminController {

    @Autowired
    private AdminService adminService;

    @RequestMapping(value = "hi", method = RequestMethod.GET)
    public String sayHi(@RequestParam String message) {
        return adminService.sayHi(message);
    }
}

测试访问

在浏览器上多次访问 http://localhost:8765/hi?message=HelloFeign

浏览器交替显示：

Hi，your message is :"HelloFeign" i am from port：8762
Hi，your message is :"HelloFeign" i am from port：8763

请求成功则表示我们已经成功实现了 Feign 功能来访问不同端口的实例