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From "Kevin Sutter (JIRA)" <j...@apache.org>
Subject [jira] Created: (OPENJPA-1516) Introduce new "clear" method on EntityManagerImpl
Date Wed, 17 Feb 2010 19:00:27 GMT
Introduce new "clear" method on EntityManagerImpl
-------------------------------------------------

                 Key: OPENJPA-1516
                 URL: https://issues.apache.org/jira/browse/OPENJPA-1516
             Project: OpenJPA
          Issue Type: Improvement
          Components: integration
    Affects Versions: 2.0.0-beta
            Reporter: Kevin Sutter
            Assignee: Kevin Sutter
             Fix For: 2.0.0


Per the JPA specification, EntityManagers are allowed to be pooled by the container by calling
the clear() method.  This clear() processing is more efficient than closing the EM and re-creating
it with every PersistenceContext injection.  This is working for the most part.

But, there are use cases where the defined clear() processing is not sufficient.  We have
run into customer situations where the connection is still active when the EM gets pooled.
 And, when this EM gets handed out to another thread/transaction, strange errors and exceptions
can occur due to the active connection.  The JPA specification and the javadoc for EM.clear()
doesn't say anything about closing out resources (connections) like the close() documentation
does.

But, the spec does allow for more efficient processing between the container and the jpa provider
(instead of relying on the clear() method) per this footnote:

[78] It is not required that these contracts be used when a third-party persistence provider
is not used: the container might use these
same APIs or its might use its own internal APIs.

In order to open the door for more efficient and more complete "clear" processing before pooling
an OpenJPA EntityManager, this JIRA is introducing a new method on our EntityManagerImpl called
prepareForPooling().  Since this is for very specific usage, I don't want to put this on the
OpenJPAEntityManager interface.  Also, I have raised this as a concern with the JPA Expert
Group and an alternative solution might be proposed in a future revision of the spec.  Containers
that wish to take advantage of this can very easily detect the existence of this method and
call prepareForPooling() instead of the clear().

Due to the customer situation, I would like to get this committed yet this week.  Please raise
any concerns with this approach immediately.  Thanks!



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