Friday, December 31, 2010

Java Persistence API Fact Sheet

The following technical details and design issues are random observations about the JPA API and Java in general.  I try to verify through experimentation every fact that appears here - but use this list at your own risk.

DI1: An EntityManager instance is not thread safe @ThreadSafe by design - however a container managed entityManager that is transactional (with default EE PersistenceContextType.TRANSACTION and default EE scoped transaction-type="JTA") is thread safe because you deal directly with a proxy wrapper provided by the enterprise container ($ProxyNN).  The container is able to manage simultaneous access to the referenced EntityManager as well as provide services via bytecode instrumentation/weaving like change tracking, security, resource management and transactions.  Therefore I recommend a container managed entityManager where possible.

3 comments:

Vishy said...
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Vishy said...

Is the thread safety (For transaction scoped EntityManager) part of JPA official specification?

PRO JPA 2 book (by Mike Keith and Merrick Schincariol) Does state that They are stateless whereas EJB in Action ( Debu Panda et al) state that They are not thread safe ( at least in injecting in servlets).

Cheryl Turner said...

Thanks for this tutorial. It helpful for me.
Máy đo đường huyết giá rẻ

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