Java TM. Message-Driven Beans. Jaroslav Porubän 2007

Transcription

1 Message-Driven Beans Jaroslav Porubän 2007

2 Java Message Service Vendor-agnostic Java API that can be used with many different message-oriented middleware Supports message production, distribution, delivery Messages exchange through virtual channels called destinations

3 Messaging Models (Messaging Domains) Point-to-point A message is consumed by a single consumer One to One Publish-and-subscribe A message is consumed by multiple consumers One to Many

4 Messaging Models Point-to-point Sender Queue Potential Receiver Potential Receiver Publish-and-subscribe Subscriber Publisher Topic Subscriber

5 Point-to-point A message is consumed by a single consumer Destination is a named queue persistent (default) messages non-persistent messages Sender (producer) sends a message to a named queue Receiver (consumer) extracts a message from the queue

6 Point-to-point Each message is held in the queue until one of the following events occurs: A message consumer successfully processes the message The message time-to-live expires If the message is non-persistent, the server on which the queue resides shuts down or fails The queue is deleted

7 Publish-and-subscribe A message is consumed by multiple consumers Destination of a message is a named topic durable messages non-durable messages Publisher (producer) publishes to a topic Subscriber (consumer) subscribes to the topic

8 Publish-and-subscribe JMS provider will save a message until one of the following events occurs: All durable subscribers successfully process the message The message time-to-live expires If the message is non-persistent, the server on which the topic resides shuts down or fails The topic is deleted

9 Non-durable vs. Durable Messages Non-durable Messages are available only during the time for which the subscriber is active If subscriber is not active (not connected), it will miss any messages supplied in its absence Durable Messages are retained on behalf of subscribers that are not available at the time the message was produced

10 JMS Client Sending a JMS message 1. Obtain ConnectionFactory and Destination = "jms/orderqueue") private Queue = "jms/orderqueuefactory") private ConnectionFactory orderqueuefactory; 2. Create a Connection, Session and objects 3. Create a MessageProducer 4. Create and send message 5. Close Session and Connection

11 JMS Client Sending a JMS message void sendmessage(long orderid) throws JMSException { Connection connection = null; Session session = null; try { connection = orderqueuefactory.createconnection(); session = connection.createsession(false, AUTO_ACKNOWLEDGE); MessageProducer messageproducer = session.createproducer(orderqueue); //Create message Message message = session.createxxxmessage();... messageproducer.send(message); } finally { if (session!= null) session.close(); if (connection!= null) connection.close(); } }

12 JMS Messages Messages are the means of communication between messaging applications A messaging system can interoperate with only the same messaging system Header Message Properties Body

13 JMS Messages Types Message types: StreamMessage MapMessage TextMessage ObjectMessage BytesMessage

14 Message-Driven Bean Overview Support the processing of asynchronous messages from a messaging system A message-driven bean retain no data or conversational state for a specific client De-coupled (Loosely-coupled) communication - anonymity

15 Message-Driven Bean Life Cycle

16 Message-Driven Bean = "jms/orderqueue", activationconfig = = "acknowledgemode", propertyvalue = = "destinationtype", propertyvalue = "javax.jms.queue") }) public class OrderProcessorBean implements MessageListener { } public void onmessage(message msg) { }...