dubbo user guider笔记之二Quick start

Quick start

这个章节较为简单，不过我们作为初学者，最好动手敲一下。加深我们对整个流程和结构的理解。

使用dubbo最普遍的方式是在spring框架中运行它。接下来的内容将引导你使用spring的xml配置的方式来开发一个dubbo应用。当然也可以使用API配置的方式。

Service provider

Defining service interfaces

DemoService.java ：

package org.apache.dubbo.demo;

public interface DemoService {
    String sayHello(String name);

}

The project structure should look like this:

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

Implement interface in service provider

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;
    }
}

Exposing service with Spring configuration

provider.xml：

<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>

这个demo使用了简单的多播作为注册中心

Configure the logging system

dubbo默认使用log4j作为日志系统，它也支持 slf4j, Apache Commons Logging, and JUL logging.
简单配置如下：
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

Bootstrap the service provider

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
    }
}

Finally, the project structure should look like this:

├── 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

Service consumer

Using the Spring configuration to reference a remote service

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>

Bootstrap the consumer

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);
    }
}

Config the logging system

This is the same as how to config it on provider side.

Finally, the project structure should be look like this:

├── 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

Start the demo

Start service provider

Run the org.apache.dubbo.demo.provider.Provider class to start the provider.

Start service consumer

Run the org.apache.dubbo.demo.provider.Consumer class to start the consumer, and you should be able to see the following result:

Hello world