HibernateJpaDialect's HibernateConnectionHandle does not call close() for Hibernate 4.x anymore, since on 4.2, the exposed Connection handle isn't a "borrowed connection" wrapper but rather the actual underlying Connection - with a close() call immediately returning the Connection to the pool and making the local handle invalid for further use within the transaction.
Also using JPA 2.0's EntityManager unwrap method now for retrieving the underlying Hibernate Session.
Issue: SPR-10395
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