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From "Abe White (JIRA)" <>
Subject [jira] Commented: (OPENJPA-119) EntityManager.clear() should not implicitly invoke the flush operation
Date Thu, 01 Feb 2007 19:53:05 GMT


Abe White commented on OPENJPA-119:

"But, since I don't know how JDO is using the kernel, it's kind of difficult for me to determine
how to make this work for both cases"

JDO needs to flush when detachAll() is called.  JPA doesn't.  Rather than changing the code
out from under JDO, how about adding a boolean to the method.  At least then JDO code (and
theoretically any other code using the method) will fail to compile.  That will allow us (and
theoretically anyone else) to see the incompatibility and update our code, rather than having
our detach behavior suddenly become incorrect.  If we later discover a better way to do it,
we can remove the boolean and fix the compile-time problems that will again result -- I'd
much rather be getting compile time errors that I'm forced to fix than to have to debug why
an obscure unit test or user case suddenly stops working at a later date.

In fact given the new (and correct) clear() behavior, I think we should add an OpenJPAEntityManager.detachAll()
method that retains the old behavior, because it is actually useful in some cases.  So the
EntityManagerImpl would end up using Broker.detachAll with both "true" and "false" flush flags.

> EntityManager.clear() should not implicitly invoke the flush operation
> ----------------------------------------------------------------------
>                 Key: OPENJPA-119
>                 URL:
>             Project: OpenJPA
>          Issue Type: Bug
>          Components: jpa
>            Reporter: Kevin Sutter
>         Assigned To: Kevin Sutter
> From the dev mailing list...
> =======================================
> We've noticed that when EntityManager.clear() is invoked, an implicit flush() is performed.
 Although the spec is cloudy in this area, I don't think this processing is correct.  The
javadoc is as follows for clear():
> /**
> * Clear the persistence context, causing all managed
> * entities to become detached. Changes made to entities that
> * have not been flushed to the database will not be
> * persisted.
> */
> public void clear();
> This indicates that Entities that have not been flushed will not be persisted.  Thus,
I would say this implies that we should not be doing an implicit flush.  If the application
wanted their Entities to be flushed before the clear, then they can call the flush() method
before calling clear().  We shouldn't be doing this for them because then they have no choice.
> The Pro EJB3 Java Persistence API book has similar wording on pages 138-139:
> "..In many respects [clear] is semantically equivalent to a transaction rollback.  All
entity instances managed by the persistence context become detached with their state left
exactly as it was when the clear() operation was invoked..."
> Our current processing for clear() eventually gets to this code:
>     public void detachAll(OpCallbacks call) {
>         beginOperation(true);
>         try {
>             if ((_flags & FLAG_FLUSH_REQUIRED) != 0)
>                 flush();
>             detachAllInternal(call);
>         } catch (OpenJPAException ke) {
>             throw ke;
>         } catch (RuntimeException re) {
>             throw new GeneralException(re);
>         } finally {
>             endOperation();
>         }
>     }
> Basically, if we have dirtied the Persistence Context, then do a flush() followed by
the detachAllInternal().  I don't think the clear() should be doing this flush() operation.
 Any disagreement? 
> =======================================
> There was no disagreement, thus this JIRA issue.

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