Hello, i'm working with GAE too, may i clarify something?
Transaction tx = pm.currentTransaction();
This is a transaction of every session?
If no, how may i handle this situation:
When one user is accessing a page i must return data from one entity from
the datastore, then close it from returning to any other users. What can be
done here?
-- Tony.
On Mon, Apr 5, 2010 at 12:08 AM, Ian Marshall <ianmarshall...@gmail.com>wrote:
>
> I have a static initialisation method and two static data members as
> follows:
>
> public class DataExchange
> {
> private static final Object objLockPMF = new Object();
> private static volatile PersistenceManagerFactory g_pmf = null;
>
> /**
> * If this class's static singleton
> <code>PersistenceManagerFactory</code>
> * is <code>null</code>, then construct it in a synchronised block of
> code.
> * @return
> * This class's static singleton
> <code>PersistenceManagerFactory</code>.
> */
> public static PersistenceManagerFactory getPersistenceManagerFactory()
> {
> if (g_pmf == null)
> synchronized(objLockPMF)
> {
> if (g_pmf == null)
> {
> loadProperties(); // My method which loads the string
> g_sDatabaseMode
> g_pmf = JDOHelper.getPersistenceManagerFactory(g_sDatabaseMode);
> }
> }
>
> return g_pmf;
> }
> }
>
>
> I then call the above static method when my Wicket application initiates by
> creating a queued task which calls this method fairly immediately but
> asynchronously. I ensure that my home page performs no data exchange, so
> creating the PMF does not delay the showing of the first page.
>
> I also call the above static method at the start of every data exchange.
> There will be nothing to construct unless the queued task has not yet
> finished or GAE has shut the relevant Wicket application instance down. For
> example (which will not be a surprise) when using a transaction:
>
> PersistenceManager pm =
> DataExchange.getPersistenceManagerFactory().getPersistenceManager();
> Transaction tx = pm.currentTransaction();
>
> try
> {
> tx.begin();
>
> //
> // Persistence code
> //
>
> tx.commit();
> }
> finally
> {
> try
> {
> if (tx.isActive()) // Because of an exception, say
> tx.rollback();
> }
> finally
> {
> pm.close();
> }
> }
>
>
> Enjoy,
>
> Ian
>
>
>
> intmanch wrote:
> >
> > Hi Ian,
> >
> > Thanks a lot for your response. I use as you PMF, not JPA, that's quite
> > simple and easy to use. Can you give me more details (code snippet) about
> > the initialization of the PMF? Is there any other point to take into
> > consideration for the performance?
> >
> --
> View this message in context:
> http://old.nabble.com/Wicket-GAE-performance-tp28118591p28133464.html
> Sent from the Wicket - User mailing list archive at Nabble.com.
>
>
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