Re: [eclipselink-users] Re: Abstract @Entities, non-abstract subclasses

[Laird Nelson <ljnelson@xxxxxxxxx>]

Excellent question; I'll check.

L

On Mon, Mar 22, 2010 at 9:56 AM, Tom Ware <tom.ware@xxxxxxxxxx> wrote:

Hi Laird,

 What is the behavior when one of these objects is read from the database? i.e. if neither of the subclasses is an entity, what is the class of the instance you get back from the DB when you read?

-Tom

Laird Nelson wrote:

Additionally, although the error chides me for not defining a public no-arg constructor (which I do, by the way), it is legal to have an @Entity that declares only a protected no-arg constructor.

Best,
Laird

On Sun, Mar 21, 2010 at 1:38 PM, Laird Nelson <ljnelson@xxxxxxxxx <mailto:ljnelson@xxxxxxxxx>> wrote:

   I have a case that is handled just fine by both Hibernate and
   OpenJPA (their JPA 2.0 implementations) and cannot be handled by
   EclipseLink 2.0.0.

   I have an abstract @Entity class.

   Then I have two concrete subclasses that are not defined as entities
   and do not add any state (they just override behavior).

   I am running this scenario in a non-Java-EE environment.

   EclipseLink barfs on EntityManagerFactory initialization, claiming
   that some class does not have a public no-argument constructor,
   which is false.  Here is the stack trace:

   Local Exception Stack:
   Exception [EclipseLink-34] (Eclipse Persistence Services -
   2.0.0.v20091127-r5931):
   org.eclipse.persistence.exceptions.DescriptorException
   Exception Description: This class does not define a public default
   constructor, or the constructor raised an exception.
   Internal Exception: java.lang.InstantiationException
   Descriptor:
   RelationalDescriptor(com.jenzabar.ngp.identity.jpa.AbstractPassiveReference
   --> [DatabaseTable(reference)])
       at
   org.eclipse.persistence.exceptions.DescriptorException.instantiationWhileConstructorInstantiation(DescriptorException.java:724)
       at
   org.eclipse.persistence.internal.descriptors.InstantiationPolicy.buildNewInstanceUsingDefaultConstructor(InstantiationPolicy.java:139)
       at
   org.eclipse.persistence.internal.descriptors.InstantiationPolicy.buildNewInstance(InstantiationPolicy.java:103)
       at
   org.eclipse.persistence.descriptors.ClassDescriptor.selfValidationAfterInitialization(ClassDescriptor.java:3519)
       at
   org.eclipse.persistence.descriptors.ClassDescriptor.validateAfterInitialization(ClassDescriptor.java:5247)
       at
   org.eclipse.persistence.descriptors.ClassDescriptor.postInitialize(ClassDescriptor.java:3241)
       at
   org.eclipse.persistence.internal.sessions.DatabaseSessionImpl.initializeDescriptors(DatabaseSessionImpl.java:463)
       at
   org.eclipse.persistence.internal.sessions.DatabaseSessionImpl.initializeDescriptors(DatabaseSessionImpl.java:406)
       at
   org.eclipse.persistence.internal.sessions.DatabaseSessionImpl.postConnectDatasource(DatabaseSessionImpl.java:671)
       at
   org.eclipse.persistence.internal.sessions.DatabaseSessionImpl.login(DatabaseSessionImpl.java:633)
       at
   org.eclipse.persistence.internal.jpa.EntityManagerFactoryProvider.login(EntityManagerFactoryProvider.java:230)
       at
   org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.deploy(EntityManagerSetupImpl.java:368)
       at
   org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.getServerSession(EntityManagerFactoryImpl.java:151)
       at
   org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManagerImpl(EntityManagerFactoryImpl.java:207)
       at
   org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManager(EntityManagerFactoryImpl.java:195)

   What is happening here?

   The JPA 2.0 specification says--explicitly--that entities may be
   abstract, and their subclasses may be concrete, so I would expect
   that this case should work.

   Thanks,
   Laird

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