Java实习日记（4)

下面将运行dubbo-demo，先来直观感受dubbo的作用。
1.先启动Zookeeper；Zookeeper的安装请参考： Java实习日记（2-1）
2.将打包好的dubbo-admin.war部署到Tomcat的webapps下，并启动；具体流程请参考：Java实习日记（2-2）
3.Eclipse中打开官网自带的dubbo-demo，先来修改以下两个配置文件：dubbo-demo-provider中的dubbo-demo-provider.xml和dubbo-demo-consumer中的dubbo-demo-consumer.xml

4.修改dubbo-demo-provider.xml中注册中心的配置
修改前 <dubbo:registry address="multicast://224.5.6.7:1234"/>
修改后 <dubbo:registry address="zookeeper://127.0.0.1:2181"/>
因为Zookeeper安装在本地，所以此处的IP地址写成127.0.0.1
dubbo-demo-provider.xml如下：

<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:dubbo="http://code.alibabatech.com/schema/dubbo"
       xmlns="http://www.springframework.org/schema/beans"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
       http://code.alibabatech.com/schema/dubbo http://code.alibabatech.com/schema/dubbo/dubbo.xsd">

    <!-- provider's application name, used for tracing dependency relationship -->
    <dubbo:application name="demo-provider"/>

    <!-- use multicast registry center to export service -->
    <!-- <dubbo:registry address="multicast://224.5.6.7:1234"/> -->
    <dubbo:registry address="zookeeper://127.0.0.1:2181"/>

    <!-- use dubbo protocol to export service on port 20880 -->
    <dubbo:protocol name="dubbo" port="20880"/>

    <!-- service implementation, as same as regular local bean -->
    <bean id="demoService" class="com.alibaba.dubbo.demo.provider.DemoServiceImpl"/>

    <!-- declare the service interface to be exported -->
    <dubbo:service interface="com.alibaba.dubbo.demo.DemoService" ref="demoService"/>

</beans>

5.同理，修改dubbo-demo-consumer.xml中注册中心的配置
修改前 <dubbo:registry address="multicast://224.5.6.7:1234"/>
修改后 <dubbo:registry address="zookeeper://127.0.0.1:2181"/>
dubbo-demo-consumer.xml如下：

<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:dubbo="http://code.alibabatech.com/schema/dubbo"
       xmlns="http://www.springframework.org/schema/beans"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
       http://code.alibabatech.com/schema/dubbo http://code.alibabatech.com/schema/dubbo/dubbo.xsd">

    <!-- consumer's application name, used for tracing dependency relationship (not a matching criterion),
    don't set it same as provider -->
    <dubbo:application name="demo-consumer"/>

    <!-- use multicast registry center to discover service -->
    <!-- <dubbo:registry address="multicast://224.5.6.7:1234"/> -->
    <dubbo:registry address="zookeeper://127.0.0.1:2181"/>

    <!-- generate proxy for the remote service, then demoService can be used in the same way as the
    local regular interface -->
    <dubbo:reference id="demoService" check="false" interface="com.alibaba.dubbo.demo.DemoService"/>

</beans>

6.先运行dubbo-demo-provider项目中的Provider，控制台打印以下信息，说明Provider启动成功

打开浏览器，输入：http://localhost:10080/dubbo-admin-2.5.8/governance/providers，账号登录，可看到以下内容，说明Provider在Zookeeper注册完成，成功的暴露出服务接口

7.紧接着运行dubbo-demo-consumer项目中的Consumer，控制台打印以下信息，说明Consumer启动成功，并成功调用Provider提供的DemoService接口

打开浏览器也会出现以下情形

至此，Dubbo官网提供的Demo已经完全成功运行，下面将结合Dubbo原理详细分析这个Demo的源码。

简单总结一下我理解的Dubbo，如有错误，请批评指正！
在分布式系统中，A模块提供接口并实现，B模块想使用A模块的接口，于是A和B都到第三方Zookeeper那里注册，A把接口暴露给zookeeper，B通过zookeeper找到A的接口实现类，直接调用来满足自己需求。
用生活的例子来理解就像是租房子，A是房东，B是租客，Zookeeper是房屋中介。