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https://issues.apache.org/jira/browse/OPENJPA-2405?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13694802#comment-13694802
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Albert Lee commented on OPENJPA-2405:
-------------------------------------
I am just pointing out that merge() is meant for merging DETACHED entity into a
persistence context. If an entity is managed by the SAME persistence context,
there is nothing to merge since the state of X is already maintained, hence the
merge operation is ignored. However, the child relationship is still processed
if proper cascade is specified.
The spec also spelled out the following;
=================================
3.2.8 Managed Instances
It is the responsibility of the application to insure that an instance is
managed in only a single persistence
context. The behavior is undefined if the same Java instance is made managed in
more than one
persistence context.
=================================
In the original test case, A (managed by em, not detached) is merged to em2
and there is no managed A in em2. Since A is marked managed and not managed in
em2, OpenJPA creates a new managed instance in em2 and eventually "INSERT" to
the database. I am not saying this is the right or wrong behavior but this use
case is undefined.
If you wants to merge changed content in A to a different persistence context,
you may have to do:
- em.find(A);
- detach A from em2
- make changes to A
- em2.find(A);
- em2.merge(A);
- commit/flush em2
> EntityManager.merge does not work for entity that is managed by another
> EntityManager
> -------------------------------------------------------------------------------------
>
> Key: OPENJPA-2405
> URL: https://issues.apache.org/jira/browse/OPENJPA-2405
> Project: OpenJPA
> Issue Type: Bug
> Affects Versions: 2.2.3
> Reporter: Arne Limburg
> Attachments: OPENJPA-2405.patch
>
>
> EntityManager.merge does not work for entity that is managed by another
> EntityManager. Instead of updating that entity OpenJPA tries to persist the
> entity a second time
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