"konstantin.ermakov" wrote : Hi!
|
| As far as I understood, after update() it is not guaranteed, that the data
is in database and commit event already happened. So, as I have the fat clients
it can be the case, that after update() was called, getObject() still returns
the old entity.
|
| My question is - is it guarateed, that after the afterCompletion() method
the database commit already happened, and it is safe to call getObject() to
receive the new data?
|
I think yes, when you use TXed messages to notify your clients. E.g. here the
meat (aka main things) how I use it:
| public class MsgProducer {
| private static HashMap<String, AtomicLong> seq =
| new HashMap<String, AtomicLong>();
| ...
| /**
| * Simple container for recording queue parameters.
| *
| * @author Jens Elkner
| * @version $Revision$
| */
| public static class QueueParams {
| Connection con;
| Session session;
| MessageProducer producer;
|
| QueueParams(Connection con, Session session, MessageProducer
producer) { this.con = con;
| this.session = session;
| this.producer = producer;
| }
|
| void destroy() {
| if (con != null) {
| try {
| con.stop();
| } catch (JMSException e) {
| // ignore
| }
| }
| if (session != null) {
| try {
| session.close();
| } catch (JMSException e) {
| // ignore
| }
| }
| if (con != null) {
| try {
| con.close();
| } catch (JMSException e) {
| // ignore
| }
| }
| }
| }
|
| /**
| * Create a message producer for the given destination.
| *
| * @param destination topic to use
| * @param tx whether to use a transaction scoped session
| * @return <code>null</code> on error, the message producer otherwise.
| */
| private static QueueParams createNewSession(String destination, boolean
tx)
| {
| try {
| ctx = new InitialContext();
| // we let the destination decide, whether it is a
| // Queue- or TopicConnectionFactory
| ConnectionFactory cf = (ConnectionFactory)
| ctx.lookup("java:/JmsXA");
| // create a Connection using the ConnectionFactory (it is not
| // necessary to start the Connection if messages are only sent)
| Connection tc = cf.createConnection();
| // create a Session using the Connection: Transaction +
| // Auto Acknowledge of the Messages
| Session s = tc.createSession(tx,
| tx ? Session.SESSION_TRANSACTED : Session.AUTO_ACKNOWLEDGE);
| // look up the Destination (either Queue or Topic) to which we
want
| // to connect in JNDI
| Destination dst = (Destination) ctx.lookup(destination);
| // create a message producer by the session and destination
acquired
| // above
| MessageProducer producer = s.createProducer(dst);
| if (producer != null) {
| params = new QueueParams(tc, s, producer);
| }
| } catch (Exception e) {
| log.error(e.getLocalizedMessage());
| failed = true;
| }
| if (failed && params != null) {
| params.destroy();
| params = null;
| }
| return params;
| }
|
| /**
| * Send a message to the given destination.
| *
| * @param destination name of the queue/topic - e.g. "topic/foo" or
| * "queue/bar".
| * @param list list of CRUD events
| */
| public static void send(String destination, CrudEventList list) {
| if (destination == null || list == null || list.getSize() == 0) {
| return;
| }
| QueueParams q = createNewSession(destination, true);
| if (q == null) {
| log.error("Unable to deliver message to '" + destination + "'");
| return;
| }
| try {
| ObjectMessage m = q.session.createObjectMessage(list);
| long msgId = getNextId(destination);
| m.setLongProperty("seq", msgId);
| if (log.isDebugEnabled()) {
| log.debug("sending CRUD message " + msgId + " to " +
destination);
| }
| q.producer.send(m);
| } catch (JMSException e) {
| log.error(e.getLocalizedMessage());
| }
| q.destroy();
| }
| ...
| }
|
So if you append something like MsgProducer.send(bla, fahsel) at the end of
your SLSB, the message would be sent only, if the TX succeeds, i.e. commit
succeeded.
Never had any out of sync problems, after changed to this pattern, so it might
be useful for you as well... ;-)
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