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https://issues.apache.org/jira/browse/OPENJPA-1966?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13214596#comment-13214596
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Vermeulen commented on OPENJPA-1966:
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We are experiencing exactly this problem with all our cascading relations of
the form A <- OneToMany -> B. We prefer using detached entities without a state
manager because we have a client-server system where the client may
insert/update entities through the server.
What we get on merging A is A' -> B'_i, with B'_i -> A.
An easy workaround for us is to manually set the reference from each B'_i to
A' after detaching.
However it would be very nice if this bug is fixed because this is easy to
forget when working with a new entity.
> Entity graphs containing bi-directional references may not merge correctly if
> an entity does not contain a state manager
> ------------------------------------------------------------------------------------------------------------------------
>
> Key: OPENJPA-1966
> URL: https://issues.apache.org/jira/browse/OPENJPA-1966
> Project: OpenJPA
> Issue Type: Bug
> Components: kernel
> Affects Versions: 1.0.4, 1.2.2, 2.0.1, 2.1.0
> Reporter: Jeremy Bauer
> Assignee: Jeremy Bauer
> Attachments: OPENJPA-1966.patch, OPENJPA-1966.patch
>
>
> An entity graph (with cascade) containing bi-directional relationships or
> circular references may fail to merge properly if one or more of the entities
> in the graph do not have a state manager - either an active or detached state
> manager. The result is that one or more of the merged entities may end up
> with a reference to a detached object. This may not be immediately evident
> and could cause problems in subsequent operations. It can even affect the
> ordering of SQL statements since foreign keys may not be properly associated
> with the detached entities.
> For example: A <- OneToOne -> B
> em.clear()
> Detached graph: B <--> A
> A: Is detached, has DetachedStateManager
> B: Is detached, No state manager, only detached state field. (ie.
> @DetachedState Object state)
> Merge: B
> After merge: B' --> A' --> B (detached)
> If B contains a state manager the result of the merge is correct: B' <--> A'
> The source of the problem is that the "no state manager" attachment path
> creates a new PC + state manager and assigns this state manager to the
> detached instance so that it can be used to attach all its fields. During a
> cascade, this detached entity (with borrowed state manager) looks persistent,
> so it can get attached into the resulting merge graph.
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