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.