The most common way to use Dubbo is to run it in Spring framework. The following content will guide you to develop a Dubbo application with Spring framework's XML configuration.
If you don't want to rely on Spring, you can try using API configuration.
First let's create a root directory called dubbo-demo:
mkdir dubbo-demo cd dubbo-demo
Next, we are going to create 3 sub-directories under root directory:
- dubbo-demo-api: the common service api
- dubbo-demo-provider: the demo provider codes
- dubbo-demo-consumer: the demo consumer codes
Service provider
Defining service interfaces
DemoService.java [1]：
package org.apache.dubbo.demo;
public interface DemoService {
String sayHello(String name);
}
The proejct 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 [2]：
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：
<?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">
<!-- provider's application name, used for tracing dependency relationship -->
<dubbo:application name="demo-provider"/>
<!-- use zookeeper registry center to export service -->
<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="org.apache.dubbo.demo.provider.DemoServiceImpl"/>
<!-- declare the service interface to be exported -->
<dubbo:service interface="org.apache.dubbo.demo.DemoService" ref="demoService"/>
</beans>
The demo uses multicast as the registry since it is simple and does not require to extra installation. If you prefer a registiry like zookeeper, please check out examples here.
Configure the logging system
Dubbo use log4j as logging system by default, it also support slf4j, Apache Commons Logging, and JUL logging.
Following is a sample configuration:
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
Complete installation steps, see：Consumer demo installation
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 zookeeper registry center to discover service -->
<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="org.apache.dubbo.demo.DemoService"/>
</beans>
Bootstrap the consumer
Consumer.java：
package org.apache.dubbo.demo.consumer;
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
Complete example
You can find the complete example code in the Github repository.
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