SpringCloud（Finchley.RELEASE版本）入门学习之————Feign服务消费者(声明式服务调用)

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一、Spring Cloud Feign的简介

Spring Cloud Feign 它是基于Netflix Feign实现，整合了Spring Cloud Ribbon 与Spring Cloud Hystrix，除了提供这两者的强大功能之外，他还提供了一种声明式的web服务端定义方式。
在Spring Cloud Feign的实现下，我们只需要创建一个接口并使用注解方式来配置他，即可完成对服务提供方接口的绑定，简化了Spring Cloud Ribbon时自行封装服务调用客户端的开发量。Spring Cloud Feign具备可插拔的注解支持，包括Feign注解和JAX-Rs注解。同时为了适应Spring 的广大用户，他在Netflix Feign的基础上扩展了对SpringMVC的注解支持。

二、搭建Spring Cloud Feign

1、和之前一样，创建一个maven工程，pom文件引入如下配置

<?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"><modelVersion>4.0.0</modelVersion><parent><artifactId>spring-Cloud</artifactId><groupId>com.demo.cloud</groupId><version>1.0-SNAPSHOT</version></parent><groupId>com.demo.cloud</groupId><artifactId>eureka-feign</artifactId><version>0.0.1-SNAPSHOT</version><packaging>jar</packaging><name>eureka-feign</name><description>Demo project for Spring Boot</description><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-web</artifactId></dependency><!--spring cloud feign --><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-openfeign</artifactId></dependency></dependencies><build><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId></plugin></plugins></build></project>

与之前相比就是多了feign的依赖

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

2、在主启动类中通过@EnableFeignClients注解开启Spring Cloud Feign 的支持。

package com.demo.cloud.eurekafeign;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.openfeign.EnableFeignClients;@EnableDiscoveryClient
@EnableFeignClients//开启Spring Cloud Feign支持
@SpringBootApplication
public class EurekaFeignApplication {public static void main(String[] args) {SpringApplication.run(EurekaFeignApplication.class, args);}}

3、yml文件指定端口、注册中心，服务名


server:port: 8765spring:application:name: eureka-feign
eureka:client:service-url:defalutZone: http://localhost:8761/eureka/

4、定义FeignService接口，通过@FeignClient注解指定服务名来绑定服务，然后再通过SpringMVC注解来绑定具体该服务提供的rest接口。

package com.demo.cloud.eurekafeign.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 = "eureka-client")
public interface FeignService {@RequestMapping(value = "hi",method = RequestMethod.GET)public String sayHi(@RequestParam(value = "message") String message);
}

注：这里服务名不区分大小写。

5、Controller调用service

package com.demo.cloud.eurekafeign.controller;import com.demo.cloud.eurekafeign.service.FeignService;
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.RestController;/*** @ClassName feginController* @Description TODO* @Author shanzz* @Date 2019/5/28 17:28* @Version 1.0**/
@RestController
public class FeginController {@Autowiredprivate FeignService feignService;@RequestMapping(value = "/hi",method = RequestMethod.GET)public String sayHi(String message){return feignService.sayHi(message);}}