初探Spring Cloud

梦幻小丑灯 发表于 2019-3-8 16:25:39

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clientSpring 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 Server1）.创建一个Maven工程helloworld.eureka.server， pom.xml内容如下：<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 /> 
</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.cloud</groupId>
         <artifactId>spring-cloud-starter-eureka-server</artifactId>
      </dependency>
      <dependency>
         <groupId>org.springframework.cloud</groupId>
         <artifactId>spring-cloud-starter-config</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）. 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表明自己是一个eureka serverserver:
port: 8761

eureka:
instance:
   hostname: 127.0.0.1
client:
   registerWithEureka: false
   fetchRegistry: false
   serviceUrl:
      defaultZone: http://127.0.0.1:8761/eureka/4) eureka server的工程结构如下server:
port: 8761

eureka:
instance:
   hostname: 127.0.0.1
client:
   registerWithEureka: false
   fetchRegistry: false
   serviceUrl:
      defaultZone: http://127.0.0.1:8761/eureka/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 Client1). 创建一个Maven工程helloworld.eureka.client， pom.xml内容如下：<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 /> 
</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).创建主类EurekaClientApplicationpackage 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.ymleureka:
client:
   serviceUrl:
         defaultZone: http://localhost:8761/eureka/
server:
port: 8762
spring:
application:
   name: service-helloworld4). Client启动后，可以访问http://localhost:87625). 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

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初探Spring Cloud