Spring Cloud Feign 入门

概述

这篇文章介绍一下如何简单的使用Feign。

什么是Feign

	Feign包含了Ribbon和Hystrix，这个在实战中才慢慢体会到它的意义，所谓的包含并不是Feign的jar包包含有Ribbon和Hystrix
的jar包这种物理上的包含，而是Feign的功能包含了其他两者的功能这种逻辑上的包含。简言之：Feign能干Ribbon和Hystrix
的事情，但是要用Ribbon和Hystrix自带的注解必须要引入相应的jar包才可以。

注意，如果代码上有什么不懂的，可以去github上看一下我写的代码，项目地址

开始项目

主要，Feign只是作为消费端，所以还要依赖Eureka 和Eureka Server两个项目。

引入pom

<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>1.5.17.RELEASE</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
		<java.version>1.8</java.version>
		<spring-cloud.version>Edgware.SR5</spring-cloud.version>
	</properties>

	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-eureka</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-feign</artifactId>
		</dependency>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</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>

在启动类上加入注解

package com.bobo;

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

@EnableFeignClients
@EnableDiscoveryClient
@SpringBootApplication
public class FeignConsumerApplication {

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

service

package com.bobo.service;

import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.stereotype.Service;
import org.springframework.web.bind.annotation.RequestMapping;

/**
 * @author [email protected]
 * @create 2018-10-28 8:59
 **/
@FeignClient(value = "eureka-client")
public interface HelloService {

    @RequestMapping(value = "hello")
    String Hello();
}

controller

package com.bobo.controller;

import com.bobo.service.HelloService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.jws.Oneway;

/**
 * @author [email protected]
 * @create 2018-10-28 9:02
 **/
@RestController
public class HelloController {


    @Autowired
    private HelloService helloService;

    @GetMapping(value = "/hello")
    public String Hello() {
        return helloService.Hello();
    }
}

配置文件

spring.application.name=feign-consumer
server.port=9001
eureka.client.serviceUrl.defaultZone=http://localhost:11111/eureka/

启动项目

首先启动 Eureka，Eureka server ，Feign-comsumer。注册中心的结果是:

Spring Cloud Feign 入门

去访问controller，结果:

Spring Cloud Feign 入门

是不是so easy呢。