Spring Cloud Eureka（二）：Eureka 注册中心体验
1、Eureka 简述
本文主要从应用角度体验一下注册中心的搭建和使用，后文会由浅入深学习Spring Cloud Eureka 的各种原理和机制。
Spring Cloud Eureka 是 Spring Cloud Netflix 组件的一部分，而 Spring Cloud Netflix 又是基于 netflix 的 eureka 封装，所以最终的源码实现在于 eureka 中。废话不多说，先上手体验一下，后文在一步步深入了解。
2、Eureka Server 服务端搭建
1、创建项目，添加 maven 依赖
<modelVersion>4.0.0</modelVersion><artifactId>lkf-cloud-eureka</artifactId><version>0.0.1-SNAPSHOT</version><packaging>jar</packaging><name>lkf-cloud-eureka</name><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.0.4.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>Finchley.SR1</spring-cloud.version></properties><dependencies><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-netflix-eureka-server</artifactId></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-config-server</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>${spring-cloud.version}</version><type>pom</type><scope>import</scope></dependency></dependencies></dependencyManagement>
2、创建启动类，启用注册中心服务 @EnableEurekaServer
@SpringBootApplication@EnableEurekaServerpublic class EurekaApplication {public static void main(String[] args) { SpringApplication.run(EurekaApplication.class, args);}}
3、添加配置文件 appication
server.port=8888eureka.instance.hostname=localhost#由于该应用为注册中心,所以设置为false,代表不向注册中心注册自己eureka.client.register-with-eureka=false#由于注册中心的职责就是维护服务实例,它并不需要去检索服务,所以也设置为falseeureka.client.fetch-registry=falseeureka.client.service-url.defaultZone=http://${eureka.instance.hostname}:${server.port}/eureka/eureka.server.wait-time-in-ms-when-sync-empty=0#eureka.instance.prefer-ip-address=true#eureka.instance.ip-address=127.0.0.1spring.application.name=lkf-cloud-eurekaspring.cloud.config.uri=${CONFIG_SERVER_URL:http://localhost:8888}
4、启动 Eureka Server 服务
启动应用，访问http://localhost:8888/，可以看到 Eureka Server 自带的 UI 管理界面。
3、Eureka Client 客户端搭建
1、创建项目 lkf-eureka-client，添加maven 依赖
<modelVersion>4.0.0</modelVersion><artifactId>lkf-eureka-client</artifactId><version>0.0.1-SNAPSHOT</version><packaging>jar</packaging><name>lkf-eureka-client</name><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.0.4.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>Finchley.SR1</spring-cloud.version></properties><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-test</artifactId><scope>test</scope></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></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>
这里如果没有引用 spring-boot-starter-web 会报以下错误：
Destroy method on bean with name 'scopedTarget.eurekaClient' threw an exception: org.springframework.beans.factory.BeanCreationNotAllowedException: Error creating bean with name 'eurekaInstanceConfigBean': Singleton bean creation not allowed while singletons of this factory are in destruction (Do not request a bean from a BeanFactory in a destroy method implementation!)
2、创建启动类，启用 @EnableDiscoveryClient 或 @EnableEurekaClient
/*** @author kaifeng*/@SpringBootApplication@EnableDiscoveryClientpublic class EurekaClientApplication {public static void main(String[] args) {SpringApplication.run(EurekaClientApplication.class, args);}}
3、添加配置文件
server.port=8001spring.application.name=lkf-eureka-clienteureka.client.serviceUrl.defaultZone=http://localhost:8888/eureka/
4、启动服务，访问注册中心
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