RE: [Springframework-developer] Real OpenSessionInView (only in view)

[Norris, T. <tys...@be...>]

Hi All -=20
I was re-reading this, and think it closely applies to a problem we are
having with trying to implement an "OpenSessionInViewFilter" within
weblogic.

We would like to keep using JTATransactionManager, so that we can
convert pieces of our CMT-EJB-centric application at a time.

The problem for us is that the session is using a DataSource, and there
will be 0..n transactions executed with "REQUIRES" propagation. Why is
this a problem? Because once the transaction commits or rollsback, the
DataSource connection (i.e. the session) it was using will become
unusable, causing failures in any following data access. In our case
weblogic enforces the invalidation of the connection (i.e. the session)
after either commit or rollback.

I think we could work around this by setting all methods that are "top
level" access to "REQUIRES_NEW", so that their commit/rollback does not
affect encompassing transactions.=20

I don't think the nested transaction support would help us, given that
we want to retain (as much as possible) our current transaction
interoperation, which will requires use of JTATransactionManager...

Does this sound about right as far as the limit of our options?

Thanks
tyson



-----Original Message-----
From: Daniel Miller [mailto:mi...@pa...]=20
Sent: Sunday, June 13, 2004 8:29 PM
To: spr...@li...
Subject: RE: [Springframework-developer] Real OpenSessionInView (only in
view)

James,

>Does that also mean that a new Hibernate session is created if a data
access
occurs after the exception? (Think of an app that logs application
failures
to a database.)

No, that is the problem--the same session continues to be used after the
exception occurs.

>From the Hibernate Session interface javadoc:
"If the Session throws an exception, the transaction must be rolled back
and
the session discarded. The internal state of the Session might not be
consistent with the database after the exception occurs."
http://www.hibernate.org/hib_docs/api/net/sf/hibernate/Session.html

>Also, is the discarding (shutting down) of a session handled by the
transaction manager or some other wrapper? I'm trying to understand if
the
discard behavior is the same for checked or unchecked exceptions. Our
apps
are set up to throw checked exceptions when we think the application
could
recover from the failure.

No, discarding is not handled by the transaction manager. The session
only
needs to be discarded if a HibernateException is thrown (checked). If
you
use Spring's HibernateDAOSupport for your DAO's, Spring catches the
HibernateExceptions and wraps them in DataAccessExceptions (unchecked).

>In cases where a checked exception is deemed fatal we control rollback
using:
TransactionInterceptor.currentTransactionStatus().setRollbackOnly();

A rollback wouldn't solve the problem because you would still be using
the
same (potentially damaged) session for other data accesses after the
exception occurred.

> The Hibernate session will always get discarded properly, even when
> exceptions get thrown during view rendering. If that doesn't happen in
any
> case, it's a bug in either Spring's interceptor/filter implementations
(or
> the servlet container's handling of filters, in case of
> OpenSessionInViewFilter).
>
> Juergen

Sorry Juergen, I worded my original message wrongly. The session is
always
properly discarded by Spring at the end of the request. Both the filter
and
the interceptor versions of OpenSessionInView do this correctly.
However,
they cannot tell when an exception is thrown in the middle of your
business
logic and therefore cannot discard the session and create a new one
after an
exception occurs.

Daniel


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