第一个dubbo程序

第一个dubbo程序

开始研究rpc框架，传统的服务调用都是一个接口对应几个实现类，在分布式系统中，如何将请求平均得分发给各个节点，这就需要远程调用的负载均衡了

江湖规矩，不写hello world不算入门

​ dubbo官网dubbo官网的中文文档十分友好，就从文档入手，学习这个框架

​ 这是官方的架构图，在这个图里，有着三个比较重要的角色，消费者，生产者，和注册中心，生产者会把自己的服务注册到注册中心，消费者会从注册中心订阅服务，对服务进行消费，有一个监视器会统计调用和被调用的次数

​

准备工作

​ 有了一个简单的概念后，直接写代码吧，写代码之前，先要安装注册中心zookeeper，从官网下载zookeeper解压，修改conf文件夹下的zoo.cfg

# The number of milliseconds of each tick
tickTime=2000
# The number of ticks that the initial
# synchronization phase can take
initLimit=10
# The number of ticks that can pass between
# sending a request and getting an acknowledgement
syncLimit=5
# the directory where the snapshot is stored.
# do not use /tmp for storage, /tmp here is just
# example sakes.
# 主要修改这个地方，存放数据文件
dataDir=/usr/local/zookeeper/data
# the port at which the clients will connect
clientPort=2181
# the maximum number of client connections.
# increase this if you need to handle more clients
#maxClientCnxns=60
#
# Be sure to read the maintenance section of the
# administrator guide before turning on autopurge.
#
# http://zookeeper.apache.org/doc/current/zookeeperAdmin.html#sc_maintenance
#
# The number of snapshots to retain in dataDir
#autopurge.snapRetainCount=3
# Purge task interval in hours
# Set to "0" to disable auto purge feature
#autopurge.purgeInterval=1

​ 修改后进入bin目录执行./zkServer.sh start

ZooKeeper JMX enabled by default
Using config: /usr/local/zookeeper/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED

创建项目，组织maven依赖

​ 创建最外层的项目

<?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">
    <parent>
        <artifactId>dubbo-demo</artifactId>
        <groupId>rpc</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>service</artifactId>
    <packaging>pom</packaging>
    <modules>
        <module>api</module>
        <module>core</module>
        <module>impl</module>
    </modules>

    <dependencies>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>dubbo</artifactId>
            <version>2.6.0</version>
        </dependency>
      <!-- 注册中心选用的zookeeper，要引入zookeeper的客户端 -->
        <dependency>
            <groupId>com.101tec</groupId>
            <artifactId>zkclient</artifactId>
            <version>0.10</version>
        </dependency>
    </dependencies>
</project>

​ 创建消费者模块

<?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">
    <parent>
        <artifactId>service</artifactId>
        <groupId>rpc</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>api</artifactId>

    <dependencies>
        <dependency>
            <groupId>rpc</groupId>
            <artifactId>core</artifactId>
            <version>1.0-SNAPSHOT</version>
            <scope>compile</scope>
        </dependency>
    </dependencies>

</project>

​ 创建接口定义模块，接口定义模块只定义接口结构和实体类，被生产者和消费者引用，本身不依赖任何模块（后期的单元测试里，引入core模块方便对代码进行单元测试，引入api模块就是远程接口调用了）

<?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">
    <parent>
        <artifactId>service</artifactId>
        <groupId>rpc</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>core</artifactId>


</project>

​ 创建消费者模块

<?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">
    <parent>
        <artifactId>service</artifactId>
        <groupId>rpc</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>impl</artifactId>

    <dependencies>
        <dependency>
            <groupId>rpc</groupId>
            <artifactId>core</artifactId>
            <version>1.0-SNAPSHOT</version>
            <scope>compile</scope>
        </dependency>
    </dependencies>


</project>

​ 项目结构如下

开始写代码

​ 首先是core模块里接口的结构定义，嗯，就是这么简单

package com.demo.service.core;

public interface HelloService {
    String sayHello(String world);
}

​ 有了接口，接下来在impl模块里写他的实现类

package com.demo.service.impl;

import com.demo.service.core.HelloService;

public class HelloServiceImpl implements HelloService {
    @Override
    public String sayHello(String word) {
        return "hello, " + word + ".";
    }
}

​ 接下来要将这个服务注册到注册中心

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:dubbo="http://code.alibabatech.com/schema/dubbo"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd
       http://code.alibabatech.com/schema/dubbo
       http://code.alibabatech.com/schema/dubbo/dubbo.xsd">
		<!-- 随便取 -->
    <dubbo:application name="dubbo_application"/>
  	<!-- 注册中心，zookeeper默认2181 -->
    <dubbo:registry address="zookeeper://127.0.0.1:2181"/>
  	<!-- 本服务的端口号 -->
    <dubbo:protocol name="dubbo" port="20880" />
  	<!-- 服务的接口，实现类 -->
    <dubbo:service interface="com.demo.service.core.HelloService" ref="helloService"/>
  	<!-- spring的bean -->
    <bean id ="helloService" class="com.demo.service.impl.HelloServiceImpl"/>
</beans>

​ 消费者不需要定义接口，也不需要提供实现类，需要向注册中心订阅服务

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:dubbo="http://code.alibabatech.com/schema/dubbo"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://code.alibabatech.com/schema/dubbo
        http://code.alibabatech.com/schema/dubbo/dubbo.xsd">

  	<!-- 随便取 -->
    <dubbo:application name="dubbo_application"/>
		<!-- 注册中心，需要知道去哪订阅 -->
    <dubbo:registry address="zookeeper://127.0.0.1:2181"/>

    <!-- 通过设置register可以只订阅，如果服务正在开发中，注册到注册中心后 -->
    <!-- <dubbo:registry address="zookeeper://127.0.0.1:2181" register="false"/> -->

    <!-- 启动时检查，出现了循环依赖，必须有一方先启动，通过此设置关闭检查 -->
    <dubbo:consumer check="false"/>

    <!-- url指定了点对点直连提供者，分布式最少是两个节点了，可以绕过注册中心，推荐用于开发测试环境 -->
    <dubbo:reference id="helloService" interface="com.demo.service.core.HelloService" url="dubbo://localhost:20880">
        <!-- 集群容错模式 出现失败重试其他服务器，默认是2 -->
        <dubbo:method name="sayHello" retries="2"/>
    </dubbo:reference>
</beans>

启动测试

​ 首先是生产者

package com.demo;

import org.springframework.context.support.ClassPathXmlApplicationContext;

import java.io.IOException;

public class Provider {
    public static void main(String[] args) throws IOException {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("provider.xml");
        context.start();
        // 阻塞生产者
        System.out.println(System.in.read());
    }
}

​ 启动，假装没看见红字-.-

​ 接下来是消费者

package com.demo;

import com.demo.service.core.HelloService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Consumer {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("consumer.xml");
        HelloService helloService = (HelloService) context.getBean("helloService");
        System.out.println(helloService.sayHello("world"));
    }
}

​ 启动，生产者不能关闭

​ 输出了hello world，教练，我入门了！

小结

​ 可以使用zookeeper客户端查看服务的提供者

# 启动客户端
./zkCli.sh
ls /dubbo/com.demo.service.core.HelloService/providers

​ 终端输出的就是提供者的信息，这里只有一个，用url转义了

​ 解码之后就比较清楚了，记录了我们接口的一些配置信息.