JPA in web application

Question

Hi
I have the following app struture
SC[A] which contains DC[1] type ear, DC[2] type java(not j2ee), DC[3] web DC[4] java(not j2ee). Now the DC 4 only contains the jpa entities and hence the persistence.xml .
I want to use the entity manager in DC 2 corresponding to the the PU defined in DC 4. We are not using EJB so i tried the following
in the web.xml i declared the following
<persistence-context-ref>
       <persistence-context-ref-name>persistence/Psctx</persistence-context-ref-name>
       <persistence-unit-name>PU</persistence-unit-name>
  </persistence-context-ref>
DC 2 has dependecy on DC 3 and DC4. DC 3 has dependency [compile +deploy] on DC4.
When i try and do a dependency lookup in DC2 via
class A
Context emCtx = (Context)new InitialContext().lookup("java:comp/env");
em = (EntityManager)emCtx.lookup("persistence/Psctx");
i get he following error
javax.naming.NamingException: Exception during lookup operation of object with name webContainer/applications/DC1~eap/<DC3 context>/java:comp/env/persistence/BUIPsCtx,
cannot resolve object reference. [Root exception is com.sap.engine.services.orpersistence.container.exceptions.ResourceException:
Persistence unit 'PU' requested from archive 'DC3.war' is not present in application 'DC1~eap'
or is not visible to the requested archive.
Resolved PU root archive path is 'null', resolved PU name is 'null'.
Have been racking my brain for long on this. The starnge thing id that when i try to do the same on a simple level ie the
Edited by: Vedula Bhaskar Rao on Mar 17, 2010 5:22 AM

Answer 1

Hi,
Can you tell us please which version of the server are you using ?
We have recently encountered very similar erroneous behaviour and have provided the fix.
I believe that it is very possible for you to have exactly the same problem.
As a possible work around, you can just specify the peristence context reference via class-level annotation instead of xml:
@PersistenceContext(name="persistence/Psctx",unitName="PU")
I hope that this should work!
Kindest Regards,
Krum.