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From Divya K Konoor <dikon...@in.ibm.com>
Subject Issue with OSGi-JPA entity persistence bundling
Date Fri, 28 Jun 2013 12:25:00 GMT

Hi ,

We are trying to figure out the best possible solution towards the below
explained OSGI-JPA related problem.

We use OSGi blueprint specification in WAS Liberty 8.5 version (which
internally uses Aries) . We use JPA entities for persistence . Our
requirement is as follows:

1. We have multiple JPA entities but all of them cannot be grouped together
in a single persistence bundle as different sets of JPA entities are for
different functionality/feature and grouping them together would mean
making them all tightly coupled .

2. All communication to the data source has to happen via a single
persistence unit (PU). This means that all JPA entities should be
associated with the same PU.

3. As per point 1 above, all entity classes cannot be bundled into a single
persistence bundle .The other option is to have one persistence bundle per
JPA entity class or to group JPA entities into persistence bundles based on
the functionality. Either options would mean that there are more than one
persistence bundles and at least one Persistence Unit needs to be defined
for each bundle but that might contradict the requirement in point 2 above.

a) Can more than one persistence unit talk to the same Data
source/Database ? If this is possible , then each persistence bundle can
define it's own PU but all of them will talk to the same back-end. Does
this approach have any undesirable implications ?
b) If the approach in 3a is feasible , then can a client bundle have a
handle to more than one entity manager and perform operations using  on
different JPA entities ? Would this cause any issues ?

4. To satisfy requirements 1 and 2 as stated above, we have currently
resorted to defining one persistence bundle with one Persistence unit .This
also carries abstract and super class entity classes. The rest of the
entity classes are packaged as OSGi fragments with the persistence bundle
as the host bundle.However, this model runs us into Entity enhancement
issues as it does not comply with OSGI 4.2 specification section 127 which
talks about how OSGi JPA entities cannot be fragments .

Looking forth to some suggestions and recommendations.

Thanks
Divya



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