I've been experimenting with extending the OpenJPA implementation.  My first
experiment was just extending the OpenJPA PersistenceProviderImpl class and
selectively enhancing a couple of methods.  At first, this looked to be
rather straight forward.  But, then I ran into a problem with the
ConfigurationProviderImpl load() method since it did some validation to make
sure that a requested PersistenceProvider element was equal to the currently
executing class:

       if (!StringUtils.isEmpty(providerName)
           return false;

Since I have extended the PersistenceProviderImpl class, this test failed.

I considered modifying the above conditional to be more lenient of
openjpa-derived persistence providers, but Patrick pointed out (via a
separate e-mail) that we might end up with some false positives when a
specific persistence provider is requested.  Thus, we decided to move this
conversation to the dev mailing list to get a discussion started.

From what I can tell, we have the PersistenceProviderImpl, the
ConfigurationProvider Service, and the ProductDerivation Service that can
help develop a proper OpenJPA derivative.  Even my brief experimentation
with extending the PersistenceProviderImpl showed that this would not be
useful without extending the ConfigurationProviderImpl (or providing a
replacement implementation).

So, is there a defined mechanism and process for extending the OpenJPA
persistence provider?  If not, any good starting points?  I'm happy to do
the experimentation.  I just would like to fit within the defined framework.


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