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From "Kevin Sutter" <>
Subject EntityManager.clear() semantics
Date Tue, 30 Jan 2007 22:32:04 GMT
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

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) {
        try {
            if ((_flags & FLAG_FLUSH_REQUIRED) != 0)
        } catch (OpenJPAException ke) {
            throw ke;
        } catch (RuntimeException re) {
            throw new GeneralException(re);
        } finally {

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?


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