在EJB3中，一个MDB（消息驱动Bean）就是一个实现了MessageListener接口的POJO。下面就是一个简单的MDB。
@MessageDriven(activationConfig={
@ActivationConfigProperty(propertyName="destinationType",
propertyValue="javax.jms.Queue"),
@ActivationConfigProperty(propertyName="destination",
propertyValue="queue/testQueue")})
public class SimpleMDB implements MessageListener { 

public void onMessage(Message message) { 

 try { 

 System.out.println("Receive Message : " + ((TextMessage)message).getText()); 

 } catch (JMSException e) { 

 e.printStackTrace(); 

 } 

 } 

 }



它要求必须标注为@MessageDriven。它所监听Destination通过标注属性来注入。

下面是一个发送消息的StatelessBean：
@Remote
public interface IMessageSender {
public void sendMessage(String content) throws Exception;
}


@Stateless
@Remote
public class MessageSender implements IMessageSender {
@Resource(mappedName="ConnectionFactory")
private ConnectionFactory factory;

@Resource(mappedName="queue/testQueue")
private Queue queue;


public void sendMessage(String content) throws Exception {
Connection cn = factory.createConnection();

Session session = cn.createSession(false, Session.AUTO_ACKNOWLEDGE);
MessageProducer producer = session.createProducer(queue);
producer.send(session.createTextMessage(content));
}
}
这个EJB只有一个方法SendMessage。ConnectionFactory和Queue通过标注注入。

接下来是客户端： 

public class MessageSenderClient { 

 public static void main(String[] args) throws Exception { 

 Properties props = new Properties(); 

 props.setProperty(Context.INITIAL_CONTEXT_FACTORY, "org.jnp.interfaces.NamingContextFactory"); 

 props.setProperty(Context.PROVIDER_URL, "localhost:2099"); 

 Context context = new InitialContext(props); 

 IMessageSender messageSender = (IMessageSender) context.lookup("MessageSender/remote"); 

 messageSender.sendMessage("Hello"); 

 } 

 }


它通过JNDI查找到上面的EJB，然后调用sengMessage.