【SpringCloud】第三篇: 服务消费者（Feign）

2023-07-22 17:32:34

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;
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