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