Spring Cloud 入門教程(一)服務註冊

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：

<?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.lvpeng</groupId>
<artifactId>springcloud.helloworld.eureka.server</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>springcloud.helloworld.Eureka.server</name>
<description>Demo Spring Eureka Server</description>

<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.3.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>
</properties>

<dependencies>
<!--eureka server -->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-eureka</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-config</artifactId>
</dependency>
<!-- spring boot test-->
<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>Dalston.RC1</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>

<repositories>
<repository>
<id>spring-milestones</id>
<name>Spring Milestones</name>
<url>https://repo.spring.io/milestone</url>
<snapshots>
<enabled>false</enabled>
</snapshots>
</repository>
</repositories>

</project>

pom.xml

 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appication.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：

<?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.lvpeng</groupId>
<artifactId>springcloud.helloworld.eureka.client</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>springcloud.helloworld.eureka.client</name>
<packaging>jar</packaging>
<description>Demo Spring Boot Client</description>

<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.3.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>
</properties>

<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-eureka</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</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>Dalston.RC1</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>

<repositories>
<repository>
<id>spring-milestones</id>
<name>Spring Milestones</name>
<url>https://repo.spring.io/milestone</url>
<snapshots>
<enabled>false</enabled>
</snapshots>
</repository>
</repositories>

</project>

pom.xml

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application.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

 

• 參考資料：
  • Spring Cloud 官網
  • 博客： http://blog.csdn.net/forezp/article/details/70148833