> On Dec 12, 2006, at 6:24 PM, Dain Sundstrom wrote: > > > Does JPA guarantee that only one bean will be activated for a > > specific pk per transaction? > > Yes. > > > Specifically, will OpenJPA ever create more that one bean for a > > specific Class:PK in a single transaction? > > No.
The full story is a little bit more complicated with OpenJPA. JPA guarantees that object equality (==) comparison must pass for two references that point to the same database record in the same transaction. IOW, however you navigate to / query for a given record, you'll get back a reference to the same Java object in a given transaction. The complication is that in most circumstances, OpenJPA holds weak references to all objects except ones with unflushed modifications. The guarantee I outlined above still holds, since if you hold a reference to an instance, our weak reference will be maintained as well, and equality tests will pass. But if you release your reference, the instance may become garbage-collected, so if you later query for / navigate to the instance, you might end up with a different object reference. I bring all this up because it means that OpenJPA does not guarantee that the return value of System.identityHashCode() will be the same for a given record over the course of a transaction. So, be sure that you bear this restriction in mind if you use an IdentityHashMap or some equivalent structure. -Patrick _______________________________________________________________________ Notice: This email message, together with any attachments, may contain information of BEA Systems, Inc., its subsidiaries and affiliated entities, that may be confidential, proprietary, copyrighted and/or legally privileged, and is intended solely for the use of the individual or entity named in this message. If you are not the intended recipient, and have received this message in error, please immediately return this by email and then delete it.
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