初探Spring Cloud(一)
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散式系統中的公共元件(比如:配置管理,服務發現,斷路器,智慧路由,微代理,控制匯流排,一次性令牌,全域性鎖,主節點選舉, 分散式session, 叢集狀態)。協調分散式環境中各個系統,為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,並且在任何分散式環境下都能工作得非常好,小到膝上型電腦, 大到資料中心和雲平臺。
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建立的各個微服務應用。要管理分散式環境下的各個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伺服器,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檔案的應用都作為一個erureka client註冊上去。eureka是一個高可用的元件,它沒有後端快取,每一個例項註冊之後需要向註冊中心傳送心跳,在預設情況下erureka server也是一個eureka client ,必須要指定一個 server。
2. 建立Eureka Server
1).建立一個Maven工程helloworld.eureka.server, pom.xml內容如下:
<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.cloud</groupId> <artifactId>springcloud.helloworld.eureka.server</artifactId> <version>0.0.1-SNAPSHOT</version> <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>
2). 用Spring Boot建立一個服務類EurekaServerApplication,需要一個註解@EnableEurekaServer加在springboot工程的啟動類上
package springcloud.helloworld.eureka.server; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer; @EnableEurekaServer @SpringBootApplication public class EurekaServerApplication { public static void main(String[] args) { SpringApplication.run(EurekaServerApplication.class, args); } }
3).eureka server的配置檔案bootstrap.yml,其中registerWithEureka:false和fetchRegistry:false表明自己是一個eureka server
server:
port: 8761eureka:
instance:
hostname: 127.0.0.1
client:
registerWithEureka: false
fetchRegistry: false
serviceUrl:
defaultZone: http://127.0.0.1:8761/eureka/
4) eureka server的工程結構如下
server:
port: 8761eureka:
instance:
hostname: 127.0.0.1
client:
registerWithEureka: false
fetchRegistry: false
serviceUrl:
defaultZone: http://127.0.0.1:8761/eureka/
5)啟動eureka server,然後訪問http://localhost:8761, 介面如下, "No instances available" 表示無client註冊
3. 建立Eureka Client
1). 建立一個Maven工程helloworld.eureka.client, pom.xml內容如下:
<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.cloud</groupId>
<artifactId>springcloud.helloworld.eureka.client</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>springcloud.helloworld.eureka.client</name>
<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>
2). 建立主類EurekaClientApplication
package springcloud.helloworld.eureka.client;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
@SpringBootApplication
@EnableEurekaClient
public class EurekaClientApplication {
public static void main(String[] args) {
SpringApplication.run(EurekaClientApplication.class, args);
}
@Value("${server.port}")
String port;
@RequestMapping("/")
public String home() {
return "hello world from port " + port;
}
}
3) eureka client的配置檔案bootstrap.yml
eureka:
client:
serviceUrl:
defaultZone: http://localhost:8761/eureka/
server:
port: 8762
spring:
application:
name: service-helloworld
4). Client啟動後, 可以訪問http://localhost:8762
5). 再次訪問伺服器埠, 可以看到Service Helloworld已經自動註冊到之前的server中