[JPA Service] allow a JPA Service to use the (non-)jta-data-source attribute instead of the javax.persistence.jdbc.driver property

[bjhargrave]

Original bug ID: BZ#247
From: Christoph Läubrich <mail@laeubi-soft.de>
Reported version: R7

[bjhargrave]

Comment author: Christoph Läubrich <mail@laeubi-soft.de>

In persitence.xml one can define jta-data-source/non-jta-data-source attribute that point to a JNDI defined datasource.

This is often used in container managed applications as it frees the persistence.xml from configuration of the actual datasource to use and let it be defined in a system-wide manner.

Currently the specification requires that

Providers must use the javax.persistence.jdbc.driver property
as defined in JDBC Access in JPA, to obtain a Data Source Factory
service.

The proposal is that (depending on the transaction type) a provider is also allowed to complete a persitence-unit if it is able to acquire the jta-data-source/non-jta-data-source from the JNDI factory at the time where a completion is should be performed.