Spring Cloud 服务注册和发现 (Service Discovery Eureka) Simple Demo

Spring Cloud 为构建微服务分布式系统中提供很多的工具，本示例以服务的注册和发现为例来演示使用Eureka来完成。

一、版本与工具

版本：

Spring Boot 2.0.2.RELEASE
Spring Cloud Finchley.RC2
JDK 1.8

工具：

Maven
Eclipse

二、项目结构

为了统一版本，采用一个项目多个模块的方式，创建一个 spring-cloud-eureka-hello-demo 项目，在其中创建 spring-cloud-eureka-server，spring-cloud-service-consumer， spring-cloud-service-provider 三个模块：

三、Eureka Server

在Eureka Server模块，首先需要引入 spring-cloud-starter-netflix-eureka-server 依赖，然后添加 @EnableEurekaClient 注解，最后在配置相关设置。

pom.xml

<?xml version="1.0"?>
<project
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
	xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
	<modelVersion>4.0.0</modelVersion>
	<parent>
		<groupId>com.devnp</groupId>
		<artifactId>spring-cloud-eureka-hello-demo</artifactId>
		<version>0.0.1-SNAPSHOT</version>
	</parent>
	<artifactId>spring-cloud-service-consumer</artifactId>

	<name>spring-cloud-service-consumer</name>
	<url>http://maven.apache.org</url>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
	</properties>

	<dependencies>
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
		</dependency>
	</dependencies>

</project>

application.yaml 配置：

server:
  port: 8761
  
spring:
  application:
    name: spring-cloud-eureka-server
    

eureka:
  instance:
    hostname: localhost
  client:
    register-with-eureka: false
    fetch-registry: false

添加注解：

package com.devnp.springcloudeurekaserver;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;

/**
 * @author duliu
 *
 */
@SpringBootApplication
@EnableEurekaServer
public class SpringCloudEurekaServerApplication {

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

四、服务提供者

在服务提供者这个模块在代码上和普通的提高RESTful API并没有多大的特别，只需要添加Eureka Client相关依赖和配置即可。

application.yaml 配置：

server:
  port: 8001

spring:
  application:
    name: spring-cloud-service-provider

eureka:
  instance:
    hostname: localhost
    instanceId: ${spring.application.name}:${spring.application.instance_id:${server.port}}
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/

RESTful API 接口 ProviderController.java

package com.devnp.springcloudserviceprovider.web;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

/**
 * @author duliu
 *
 */
@RestController
public class ProviderController {

	@GetMapping("/hello")
	public Object hello() {
		return "Hello Wolrd!" ;
	}
}

五、服务消费者

服务者也是作为 Eureka Client，所以在都需要添加相关的依赖和配置。

在请求和一般直接请求目标的URL有不同之处，这时候需要请求 服务提供者名称/api 这样即使提供者的IP或者域名发生变化，在消费端也不需要做任何修改。

ConsumerContoller.java

package com.devnp.springcloudserviceconsumer.web;

import org.apache.commons.collections.CollectionUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

/**
 * @author duliu
 *
 */
@RestController
public class ConsumerContoller {
	
	@Autowired
	private RestTemplate restTemplate;

	@GetMapping("/hello")
	public Object hello() {
		String reponse = restTemplate.getForObject("http://spring-cloud-service-provider/hello", String.class, CollectionUtils.EMPTY_COLLECTION);
		
		return reponse ;
	}
}

RestTemplate 是需要手动去完成配置：

SpringCloudServiceConsumerApplication.java

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.context.annotation.Bean;
import org.springframework.http.client.ClientHttpRequestFactory;
import org.springframework.http.client.SimpleClientHttpRequestFactory;
import org.springframework.web.client.RestTemplate;

/**
 * @author duliu
 *
 */
@SpringBootApplication
@EnableEurekaClient
public class SpringCloudServiceConsumerApplication {

	@Bean
	@LoadBalanced
	public RestTemplate restTemplate(ClientHttpRequestFactory factory) {
		return new RestTemplate(factory);
	}

	@Bean
	public ClientHttpRequestFactory simpleClientHttpRequestFactory() {
		SimpleClientHttpRequestFactory factory = new SimpleClientHttpRequestFactory();
		factory.setReadTimeout(5000);// ms
		factory.setConnectTimeout(15000);// ms
		return factory;
	}
	
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		SpringApplication.run(SpringCloudServiceConsumerApplication.class, args);
	}

}