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:
<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
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的配置文件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)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:
<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). 創建主類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的配置文件bootstrap.yml
eureka:
client:
serviceUrl:
defaultZone: http://localhost:8761/eureka/
server:
port: 8762
spring:
application:
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