ex8_14.txt

j2ee core design patterns

Example 8.14 	POJO Service Activator: OrderServiceActivator.java
// imports. . . 

public class OrderServiceActivator implements javax.jms.MessageListener{

	// Queue session and receiver: see JMS API for details
	private QueueSession orderQueueSession;
	private QueueReceiver orderQueueReceiver;

	// Note: values should come from property files or
	// environment. Hard coded here for illustration only
    private String connectionFactoryName =
			"PendingOrdersQueueFactory";
	private String queueName = "PendingOrders";

	// use a service locator to locate administered JMS
	// components such as a Queue or a Queue Connection factory
	private ServiceLocator serviceLocator;
	private QueueConnectionFactory queueConnectionFactory;
	private QueueConnection queueConnection;

	public OrderServiceActivator(
			String connectionFactoryName, String queueName) {
		super();
		this.connectionFactoryName = connectionFactoryName;
		this.queueName = queueName;
		startListener();
	}

	private void startListener() {
		try {
			serviceLocator = ServiceLocator.getInstance();
			queueConnectionFactory =
			serviceLocator.getQueueConnectionFactory(
					connectionFactoryName);
			queueConnection =
					queueConnectionFactory.createQueueConnection();

			// See JMS API for method usage and arguments
			orderQueueSession =
					queueConnection.createQueueSession (...);
			Queue ordersQueue =
					serviceLocator.getQueue(queueName);
			orderQueueReceiver =
					orderQueueSession.createReceiver(ordersQueue);
			orderQueueReceiver.setMessageListener(this);
		}
		catch (JMSException excp) {
			// handle error
		}
	}

	// The JMS API specifies the onMessage method in the
	// javax.jms.MessageListener interface. 
	// This method is asynchronously invoked 
	// when a message arrives on the Queue being
	// listened to by the ServiceActivator.    
	// See JMS Specification and API for more details.
	public void onMessage(Message message) {
		try {
			// parse Message msg. See JMS API for Message.
			// Get the order object from the message
			ObjectMessage objectMessage =
					(javax.jms.ObjectMessage) message;
			Order order = (Order) objectMessage.getObject();

			// Use the Business Delegate for Order Processor
			// Session Fa鏰de to invoke order processing
			OrderProcessorDelegate orderProcessorBD =
					new OrderProcessorDelegate();
			orderProcessorBD.processOrder(order);

			// send any response here...
		}
		catch (JMSException jmsexcp) {
 			// Handle JMSExceptions, if any
			// Send error response, throw runtime exception
		} 
		catch (Exception excp) {
			// Handle any other exceptions
			// Send error response, throw runtime exception
		}
	}
  	public void close() {
		try {
			// cleanup before closing
			orderQueueReceiver.setMessageListener (null);   
			orderQueueSession.close();     
		}
		catch(Exception excp) {
			// Handle exception - Failure to close
		}
	}
}