NullPointerException Thrown on IndirectList

Question

Hello All:
I recently encountered some odd behavior when working with an object type that is mapped as one-to-many to another object type using transparent indirection. Specifically, a NullPointerException is being thrown on the call to the size method of IndirectList during the committing of changes to the database.
The scenario is as follows. I have an object A that is mapped as one-to-many to object B using transparent indirection. Object A is constructed such that it contains an empty Vector object that will contain B objects. In my scenario, object A is read from the database and already exists but no B objects have yet been associated with A. When I do add B objects to the list and commit the changes, I am seeing a NullPointerException being thrown on the call to the size method of the IndirectList object. The console log shows the following error.
10:18:51.742--UnitOfWork(385685245)--Thread[Thread-27,5,main]--java.lang.NullPointerExceptionjava.lang.NullPointerException
     at oracle.toplink.indirection.IndirectList.size(IndirectList.java:611)
     at oracle.toplink.internal.queryframework.CollectionContainerPolicy.sizeFor(CollectionContainerPolicy.java:147)
     at oracle.toplink.internal.indirection.TransparentIndirectionPolicy.getRealAttributeValueFromObject(TransparentIndirectionPolicy.java:246)
     at oracle.toplink.mappings.ForeignReferenceMapping.getRealAttributeValueFromObject(ForeignReferenceMapping.java:345)
     at oracle.toplink.mappings.CollectionMapping.getRealAttributeValueFromObject(CollectionMapping.java:536)
     at oracle.toplink.mappings.CollectionMapping.getRealCollectionAttributeValueFromObject(CollectionMapping.java:550)
     at oracle.toplink.mappings.CollectionMapping.compareForChange(CollectionMapping.java:189)
     at oracle.toplink.internal.descriptors.ObjectBuilder.compareForChange(ObjectBuilder.java:825)
     at oracle.toplink.publicinterface.UnitOfWork.calculateChanges(UnitOfWork.java:438)
     at oracle.toplink.publicinterface.UnitOfWork.commitToDatabaseWithChangeSet(UnitOfWork.java:1135)
     at oracle.toplink.publicinterface.UnitOfWork.commitRootUnitOfWork(UnitOfWork.java:956)
     at oracle.toplink.publicinterface.UnitOfWork.commitAndResume(UnitOfWork.java:812)
Alternately, I noticed that when executing the same scenario with the only difference being object A does not exist in the database and must be constructed, the commit call does not throw the exception and succeeds.
I am utilizing Toplink 9.0.4.5. What can I do to ensure the exception is not thrown? This behavior seems strange to me.
Thanks in advance for your time.

Answer 1

This is an odd error. It seems to be occurring because the ValueHolder inside your IndirectList contains null, but I'm not sure how this could occur. Do you ever access the IndirectList or its ValueHolder directly? Do you initial your object's variable to a new Vector() or a new IndirectList()? (you should use new Vector())
It is also odd, because you add method would have already instantiated the indirect list, and if its collection was null, should have already got the null-pointer. Does your add method do anything special? You can check the state of the object's indirect list before you call commit to see if its' value is null.
Otherwise, you could try the latest 9.0.4 patch release, or try the 10.1.3 release, or contact Oracle technical support on the issue.