1. 什麼是Spring Cloud？
Spring提供了一系列工具，可以幫助開發人員迅速搭建分佈式系統中的公共組件（比如：配置管理，服務發現，斷路器，智能路由，微代理，控制總線，一次性令牌，全局鎖，主節點選舉， 分佈式session, 集羣狀態）。協調分佈式環境中各個系統，爲各類服務提供模板性配置。使用Spring Cloud, 開發人員可以搭建實現了這些樣板的應用，並且在任何分佈式環境下都能工作得非常好，小到筆記本電腦， 大到數據中心和雲平臺。
Spring Cloud官網的定義比較抽象，我們可以從簡單的東西開始。Spring Cloud是基於Spring Boot的， 最適合用於管理Spring Boot創建的各個微服務應用。要管理分佈式環境下的各個Spring Boot微服務，必然存在服務的註冊問題。所以我們先從服務的註冊談起。既然是註冊，必然有個管理註冊中心的服務器，各個在Spring Cloud管理下的Spring Boot應用就是需要註冊的client
Spring Cloud使用erureka server, 然後所有需要訪問配置文件的應用都作爲一個erureka client註冊上去。eureka是一個高可用的組件，它沒有後端緩存，每一個實例註冊之後需要向註冊中心發送心跳，在默認情況下erureka server也是一個eureka client ,必須要指定一個 server。
2. 創建Eureka Server
1）.創建一個Maven工程helloworld.eureka.server， pom.xml內容如下：
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創建一個服務類EurekaServerApplication，需要一個註解@EnableEurekaServer加在springboot工程的啓動類上
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表明自己是一個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的工程結構如下
5）啓動eureka server，然後訪問http://localhost:8761, 界面如下， "No instances available" 表示無client註冊
3. 創建Eureka Client
1). 創建一個Maven工程helloworld.eureka.client， pom.xml內容如下：
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). 創建主類EurekaClientApplication
使用@EnableEurekaClient註解表明是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啓動後， 可以訪問http://localhost:8762
5). 再次訪問服務器端口, 可以看到Service Helloworld已經自動註冊到之前的server中
