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From "Kevin Sutter (JIRA)" <j...@apache.org>
Subject [jira] Updated: (OPENJPA-1516) Introduce new "clear" method on EntityManagerImpl
Date Wed, 17 Feb 2010 19:26:28 GMT

     [ https://issues.apache.org/jira/browse/OPENJPA-1516?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Kevin Sutter updated OPENJPA-1516:
----------------------------------

    Attachment: openjpa-1516.patch

Proposed patch for new prepareForPooling() method on EntityManagerImpl.

> 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
>
>         Attachments: openjpa-1516.patch
>
>
> 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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