深入掌握JMS（十二）：MDB

在EJB3中，一個MDB（訊息驅動Bean）就是一個實現了MessageListener介面的POJO。下面就是一個簡單的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();
                    }
                }
            }

            它要求必須標註為@MessageDriven。它所監聽Destination通過標註屬性來注入。

            下面是一個發送訊息的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));
                }
            }
            這個EJB只有一個方法SendMessage。ConnectionFactory和Queue通過標註注入。

            接下來是用戶端：
            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");
                }
            }
            它通過JNDI尋找到上面的EJB，然後調用sengMessage.