Description Martin S. 2009-07-06 20:12:46 EDT

In practice data is read more often than created, updated or deleted. In EclipseLink/JPA we will always get a clone back from any find() or query. But this can be very expensive, because first the entity in the session cache must be cloned and second it must be garbage collected again. This is not necessary if the data is only read.

It would be nice if there was an entity manager that always returns read-only objects (references to the objects in the session cache) instead of cloned objects. In practice, such an entity manager would be used for all read operations. This would be a huge performance improvement because it avoids cloning and garbage collection completely.

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Please also take a look at this:

http://www.nabble.com/JPA-non-transactional-method-and-entity-access%3A-Do-I-get-a-reference-to-the-entity-or-a-clone-of-the-entity-in-the-session-cache--td22790869.html