1. 什么是Spring Cloud？
Spring提供了一系列工具，可以帮助开发人员迅速搭建分布式系统中的公共组件（比如：配置管理，服务发现，断路器，智能路由，微代理，控制总线，一次性令牌，全局锁，主节点选举， 分布式session, 集群状态）。协调分布式环境中各个系统，为各类服务提供模板性配置。使用Spring Cloud, 开发人员可以搭建实现了这些样板的应用，并且在任何分布式环境下都能工作得非常好，小到笔记本电脑， 大到数据中心和云平台。
Spring Cloud官网的定义比较抽象，我们可以从简单的东西开始。Spring Cloud是基于Spring Boot的， 最适合用于管理Spring Boot创建的各个微服务应用。要管理分布式环境下的各个Spring Boot微服务，必然存在服务的注册问题。所以我们先从服务的注册谈起。既然是注册，必然有个管理注册中心的服务器，各个在Spring Cloud管理下的Spring Boot应用就是需要注册的client
Spring Cloud使用erureka server, 然后所有需要访问配置文件的应用都作为一个erureka client注册上去。eureka是一个高可用的组件，它没有后端缓存，每一个实例注册之后需要向注册中心发送心跳，在默认情况下erureka server也是一个eureka client ,必须要指定一个 server。
2. 创建Eureka Server
1）.创建一个Maven工程helloworld.eureka.server， pom.xml内容如下：
1 <?xml version="1.0" encoding="UTF-8"?> 2 <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 3 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> 4 <modelVersion>4.0.0</modelVersion> 5 <groupId>com.chry</groupId> 6 <artifactId>springcloud.helloworld.eureka.server</artifactId> 7 <version>0.0.1-SNAPSHOT</version> 8 <packaging>jar</packaging> 9 <name>springcloud.helloworld.Eureka.server</name> 10 <description>Demo Spring Eureka Server</description> 11 12 <parent> 13 <groupId>org.springframework.boot</groupId> 14 <artifactId>spring-boot-starter-parent</artifactId> 15 <version>1.5.3.RELEASE</version> 16 <relativePath/> <!-- lookup parent from repository --> 17 </parent> 18 19 <properties> 20 <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> 21 <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding> 22 <java.version>1.8</java.version> 23 </properties> 24 25 <dependencies> 26 <!--eureka server --> 27 <dependency> 28 <groupId>org.springframework.cloud</groupId> 29 <artifactId>spring-cloud-starter-eureka</artifactId> 30 </dependency> 31 <dependency> 32 <groupId>org.springframework.cloud</groupId> 33 <artifactId>spring-cloud-starter-eureka-server</artifactId> 34 </dependency> 35 <dependency> 36 <groupId>org.springframework.cloud</groupId> 37 <artifactId>spring-cloud-starter-config</artifactId> 38 </dependency> 39 <!-- spring boot test--> 40 <dependency> 41 <groupId>org.springframework.boot</groupId> 42 <artifactId>spring-boot-starter-test</artifactId> 43 <scope>test</scope> 44 </dependency> 45 </dependencies> 46 47 <dependencyManagement> 48 <dependencies> 49 <dependency> 50 <groupId>org.springframework.cloud</groupId> 51 <artifactId>spring-cloud-dependencies</artifactId> 52 <version>Dalston.RC1</version> 53 <type>pom</type> 54 <scope>import</scope> 55 </dependency> 56 </dependencies> 57 </dependencyManagement> 58 59 <build> 60 <plugins> 61 <plugin> 62 <groupId>org.springframework.boot</groupId> 63 <artifactId>spring-boot-maven-plugin</artifactId> 64 </plugin> 65 </plugins> 66 </build> 67 68 <repositories> 69 <repository> 70 <id>spring-milestones</id> 71 <name>Spring Milestones</name> 72 <url>https://repo.spring.io/milestone</url> 73 <snapshots> 74 <enabled>false</enabled> 75 </snapshots> 76 </repository> 77 </repositories> 78 79 </project>
2）. 用Spring Boot创建一个服务类EurekaServerApplication，需要一个注解@EnableEurekaServer加在springboot工程的启动类上
1 package springcloud.helloworld.eureka.server;
2
3 import org.springframework.boot.SpringApplication;
4 import org.springframework.boot.autoconfigure.SpringBootApplication;
5 import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;
6
7 @EnableEurekaServer
8 @SpringBootApplication
9 public class EurekaServerApplication {
10
11 public static void main(String[] args) {
12 SpringApplication.run(EurekaServerApplication.class, args);
13 }
14 }
3).eureka server的配置文件application.yml，其中registerWithEureka：false和fetchRegistry：false表明自己是一个eureka server
1 server:
2 port: 8761
3
4 eureka:
5 instance:
6 hostname: localhost
7 client:
8 registerWithEureka: false
9 fetchRegistry: false
10 serviceUrl:
11 defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/
4) eureka server的工程结构如下
5）启动eureka server，然后访问http://localhost:8761, 界面如下， "No instances available" 表示无client注册
3. 创建Eureka Client
1). 创建一个Maven工程helloworld.eureka.client， pom.xml内容如下：
1 <?xml version="1.0" encoding="UTF-8"?> 2 <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"> 3 <modelVersion>4.0.0</modelVersion> 4 <groupId>com.chry</groupId> 5 <artifactId>springcloud.helloworld.eureka.client</artifactId> 6 <version>0.0.1-SNAPSHOT</version> 7 <name>springcloud.helloworld.eureka.client</name> 8 <packaging>jar</packaging> 9 <description>Demo Spring Boot Client</description> 10 11 <parent> 12 <groupId>org.springframework.boot</groupId> 13 <artifactId>spring-boot-starter-parent</artifactId> 14 <version>1.5.3.RELEASE</version> 15 <relativePath/> <!-- lookup parent from repository --> 16 </parent> 17 18 <properties> 19 <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> 20 <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding> 21 <java.version>1.8</java.version> 22 </properties> 23 24 <dependencies> 25 <dependency> 26 <groupId>org.springframework.cloud</groupId> 27 <artifactId>spring-cloud-starter-eureka</artifactId> 28 </dependency> 29 <dependency> 30 <groupId>org.springframework.boot</groupId> 31 <artifactId>spring-boot-starter-web</artifactId> 32 </dependency> 33 34 <dependency> 35 <groupId>org.springframework.boot</groupId> 36 <artifactId>spring-boot-starter-test</artifactId> 37 <scope>test</scope> 38 </dependency> 39 </dependencies> 40 41 <dependencyManagement> 42 <dependencies> 43 <dependency> 44 <groupId>org.springframework.cloud</groupId> 45 <artifactId>spring-cloud-dependencies</artifactId> 46 <version>Dalston.RC1</version> 47 <type>pom</type> 48 <scope>import</scope> 49 </dependency> 50 </dependencies> 51 </dependencyManagement> 52 53 <build> 54 <plugins> 55 <plugin> 56 <groupId>org.springframework.boot</groupId> 57 <artifactId>spring-boot-maven-plugin</artifactId> 58 </plugin> 59 </plugins> 60 </build> 61 62 <repositories> 63 <repository> 64 <id>spring-milestones</id> 65 <name>Spring Milestones</name> 66 <url>https://repo.spring.io/milestone</url> 67 <snapshots> 68 <enabled>false</enabled> 69 </snapshots> 70 </repository> 71 </repositories> 72 73 74 </project>
2). 创建主类EurekaClientApplication
使用@EnableEurekaClient注解表明是client
1 package springcloud.helloworld.eureka.client;
2
3 import org.springframework.beans.factory.annotation.Value;
4 import org.springframework.boot.SpringApplication;
5 import org.springframework.boot.autoconfigure.SpringBootApplication;
6 import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
7 import org.springframework.web.bind.annotation.RequestMapping;
8 import org.springframework.web.bind.annotation.RequestParam;
9 import org.springframework.web.bind.annotation.RestController;
10
11 @SpringBootApplication
12 @EnableEurekaClient
13 @RestController
14
15 public class EurekaClientApplication {
16
17 public static void main(String[] args) {
18 SpringApplication.run(EurekaClientApplication.class, args);
19 }
20
21 @Value("${server.port}")
22 String port;
23 @RequestMapping("/")
24 public String home() {
25 return "hello world from port " + port;26 }
27
28 }
3) eureka client的配置文件appication.yml
1 eureka: 2 client: 3 serviceUrl: 4 defaultZone: http://localhost:8761/eureka/ 5 server: 6 port: 8762 7 spring: 8 application: 9 name: service-helloworld
4). Client启动后， 可以访问http://localhost:8762
5). 再次访问服务器端口, 可以看到Service Helloworld已经自动注册到之前的server中
