In Glassfish each deployed app gets its own class loader, so each class loader
loads its own provider class and as a result, each persistence.xml is processed
completely separately.
Now, if your webserver (Tomcat or any other) has everything loaded by a single
class loader, you have the same situation as you would in a Java SE environment,
and only 1 PU with a specific name can exist.
Now, that said, you do not need to change .java classes, only PU names in the
persistence.xml (you already have different datasources or driver properties in
those files, right?) to avoid the problem your are getting into.
Best regards,
-marina
Edson Carlos Ericksson Richter wrote:
> I getting things clear.
> Scenario is:
>
> I have one server, and need to deploy same application twice, but one
> should not access database information from another.
> So, when I "build" application on NetBeans, I have a custom ANT build
> step that changes all .XML files to point to correct database - but I
> would not change .java files (where PU is defined).
>
> About point 1 you highlited, I think is exactly problem I'm facing
> (since I have two applications using a static PersistenceManager it's
> being tied up to one classloader !?).
> About point 2, my expectation is two applications having same PU name
> access different databases (and have own cache - so they don't trows
> ClassCastException when loading a Customer from Database).
>
> So, the point is: is possible to load PersistenceContext from JNDI in
> either Tomcat and Glassfish, so I don't need two different pieces of
> code for each server?
>
> Thanks for help!
>
> Edson Richter
>
>
>
> glassfish_at_javadesktop.org escreveu:
>
>> Whether TopLink will work in your scenario or not, will depend on 2
>> things - your expectations and the class loader.
>> 1. The class loader. In the same class loader, there can be only one
>> PU with a particular name. I think there is an open issue to allow the
>> same name but different overrides as specified in the map that you
>> pass to Persistence.createEMF() call.
>>
>> 2. Expectations. Do you expect those two apps to share a PU or have
>> their own copies? Depending on how Tomcat handles class loaders (GF
>> uses a separate class loader for each application), you'll get a
>> different answer to your original question.
>>
>> Regards,
>> -marina
>> [Message sent by forum member 'mvatkina' (mvatkina)]
>>
>> http://forums.java.net/jive/thread.jspa?messageID=223161
>>
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