Dubbo之快速开始

使用Dubbo最常用的方式是与Spring Framework集成。下面内容，基于Spring Framework的XML配置，引导你开发一个Dubbo应用。如果不想依赖Spring，也可以试一下API配置。

首先创建名为dubbo-demo的根目录：

mkdir dubbo-demo
cd dubbo-demo

接下来在根目录下创建三个子目录：

• dubbo-demo-api：普通的服务API。
• dubbo-demo-provider：服务供应者演示代码。
• dubbo-demo-consumer：服务消费者演示代码。

服务供应者

定义服务接口

DemoService.java:

package org.apache.dubbo.demo;

public interface DemoService {
    String sayHello(String name);

}

项目结构看起来如下：

.
├── dubbo-demo-api
│   ├── pom.xml
│   └── src
│       └── main
│           └── java
│               └── org
│                   └── apache
│                       └── dubbo
│                           └── demo
│                               └── DemoService.java

 实现服务接口：

DemoServiceImpl.java:

package org.apache.dubbo.demo.provider;
import org.apache.dubbo.demo.DemoService;

public class DemoServiceImpl implements DemoService {
    public String sayHello(String name) {
        return "Hello " + name;
    }
}

配置Spring暴露服务：

<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:dubbo="http://dubbo.apache.org/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-4.3.xsd
       http://dubbo.apache.org/schema/dubbo http://dubbo.apache.org/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"/>
    <!-- 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="org.apache.dubbo.demo.provider.DemoServiceImpl"/>
    <!-- declare the service interface to be exported -->
    <dubbo:service interface="org.apache.dubbo.demo.DemoService" ref="demoService"/>
</beans>

示例使用multicast作为注册服务中心，因为它简单不需额外的安装。如果更偏向使用zookeeper，请参考这里。

配置日志系统

Dubbo默认使用log4j作为日志系统，它也支持slf4j，阿帕奇通用日志，以及JUL日志。

以下是简单配置：
log4j.properties

###set log levels###
log4j.rootLogger=info, stdout
###output to the console###
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target=System.out
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=[%d{dd/MM/yy hh:mm:ss:sss z}] %t %5p %c{2}: %m%n

引导服务提供者

Provider.java:

package org.apache.dubbo.demo.provider;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Provider {

    public static void main(String[] args) throws Exception {
        System.setProperty("java.net.preferIPv4Stack", "true");
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(new String[]{"META-INF/spring/dubbo-demo-provider.xml"});
        context.start();
        System.out.println("Provider started.");
        System.in.read(); // press any key to exit
    }
}

项目目录结构如下：

├── dubbo-demo-provider
│   ├── pom.xml
│   └── src
│       └── main
│           ├── java
│           │   └── org
│           │       └── apache
│           │           └── dubbo
│           │               └── demo
│           │                   └── provider
│           │                       ├── DemoServiceImpl.java
│           │                       └── Provider.java
│           └── resources
│               ├── META-INF
│               │   └── spring
│               │       └── dubbo-demo-provider.xml
│               └── log4j.properties

服务消费者

完整安装步骤参考：Consumer demo installation

配置Spring引用远程服务

consumer.xml:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:dubbo="http://dubbo.apache.org/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-4.3.xsd
       http://dubbo.apache.org/schema/dubbo http://dubbo.apache.org/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"/>
    <!-- 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="org.apache.dubbo.demo.DemoService"/>
</beans>

引导消费者服务

Consumer.java:

import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.apache.dubbo.demo.DemoService;
 
public class Consumer {
    public static void main(String[] args) throws Exception {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(new String[] {"META-INF/spring/dubbo-demo-consumer.xml"});
        context.start();
        // Obtaining a remote service proxy
        DemoService demoService = (DemoService)context.getBean("demoService");
        // Executing remote methods
        String hello = demoService.sayHello("world");
        // Display the call result
        System.out.println(hello);
    }
}

配置日志系统

与前述消费者服务配置相同。

最后目录结构如下：

├── dubbo-demo-consumer
│   ├── pom.xml
│   └── src
│       └── main
│           ├── java
│           │   └── org
│           │       └── apache
│           │           └── dubbo
│           │               └── demo
│           │                   └── consumer
│           │                       └── Consumer.java
│           └── resources
│               ├── META-INF
│               │   └── spring
│               │       └── dubbo-demo-consumer.xml
│               └── log4j.properties

启动演示

启动服务供应者

运行org.apache.dubbo.demo.provider.Provider类启动供应者。

启动服务消费者

运行org.apache.dubbo.demo.provider.Consumer类启动消费者，应该可以看到如下输出：

Hello world

完整示例

Github仓库完整示例代码：

• Provider demo
• Consumer demo

参考：http://dubbo.apache.org/en-us/docs/user/quick-start.html