【SpringCloud】第三篇: 服务消费者（Feign）

前言:

必需学会SpringBoot基础知识

简介:

spring cloud 为开发人员提供了快速构建分布式系统的一些工具，包括配置管理、服务发现、断路器、路由、微代理、事件总线、全局锁、决策竞选、分布式会话等等。它运行环境简单，可以在开发人员的电脑上跑。

工具:

JDK8

apache-maven-3.5.2

IntelliJ IDEA 2017.3 x64

一、Feign简介

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。

简而言之：

Feign 采用的是基于接口的注解

Feign 整合了ribbon

二、准备工作

1. 运行 eureka-server:8761;

2. 运行 eureka-client 两次，端口分别为8762 、8773

三、创建一个feign的服务

3.1 pom.xml

<?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>

	<groupId>com.lwc</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>

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>1.5.10.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.SR2</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-server</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>

</project>

3.2 通过 application.yml 跳转 application-dev.yml 配置程序名, 端口 和指定注册中心 如下:

spring:
  application:
      name: eureka-feign
  profiles:
    active: ${@profileActiv@:dev}

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/
server:
  port: 8765

3.3 启动类添加@EnableFeignClients注解开启Feign的功能：

package com.lwc;

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;

/**
 * @author Eddie
 */
@EnableFeignClients
@EnableDiscoveryClient
@SpringBootApplication
public class EurekaFeignApplication {

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

3.4 定义一个feign接口，通过@ FeignClient（“服务名”）, 通过服务名找对应服务 如下:

package com.lwc.service;

import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;

/**
 * @author eddie.lee
 * @Package com.lwc.service
 * @ClassName FeignClientService
 * @description
 * @date created in 2018-03-27 10:43
 * @modified by
 */
@FeignClient("eureka-client")
public interface FeignClientService {

    @GetMapping("/eureka/client")
    String feignToClientByName(@RequestParam("name") String name);

}

3.5 创建controller层,通过API接口,来消费Feign客户端服务. 如下:

package com.lwc.controller;

import com.lwc.service.FeignClientService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

/**
 * @author eddie.lee
 * @Package com.lwc.controller
 * @ClassName FeignController
 * @description 服务消费者（Feign）
 * @date created in 2018-03-27 10:50
 * @modified by
 */
@RestController
@RequestMapping("/eureka")
public class FeignController {

    @Autowired
    private FeignClientService feignClientService;

    @GetMapping("/feign")
    public String feign(@RequestParam("name") String name) {
        return feignClientService.feignToClientByName(name);
    }

}

四、参考资料

eureka-feign
http://localhost:8765/eureka/feign?name=eddie

标签

3-1

源码下载
https://github.com/eddie-code/SpringCloudDemo#springclouddemo

疑惑: eureka-ribbon, eureka-feign 两个功能相同, 区别在哪里?

答: feign是基于ribbon衍生出来, feign采用接口方式, 更简洁;