I am getting a NullPointerException in a hibernate API.

Trace of the exception is -

com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor
java.lang.NullPointerException
at org.hibernate.collection.PersistentBag.getSnapshot(PersistentBag.java:132)
at org.hibernate.engine.CollectionEntry.postInitialize(CollectionEntry.java:214)
at org.hibernate.engine.StatefulPersistenceContext.addInitializedCollection(StatefulPersistenceContext.java:833)
at org.hibernate.engine.loading.CollectionLoadContext.endLoadingCollection(CollectionLoadContext.java:268)
at org.hibernate.engine.loading.CollectionLoadContext.endLoadingCollections(CollectionLoadContext.java:245)
at org.hibernate.engine.loading.CollectionLoadContext.endLoadingCollections(CollectionLoadContext.java:218)
at org.hibernate.loader.Loader.endCollectionLoad(Loader.java:900)
at org.hibernate.loader.Loader.initializeEntitiesAndCollections(Loader.java:888)
at org.hibernate.loader.Loader.doQuery(Loader.java:752)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:259)
at org.hibernate.loader.Loader.loadCollection(Loader.java:2015)
at org.hibernate.loader.collection.CollectionLoader.initialize(CollectionLoader.java:59)
at org.hibernate.persister.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:587)
at org.hibernate.event.def.DefaultInitializeCollectionEventListener.onInitializeCollection(DefaultInitializeCollectionEventListener.java:83)
at org.hibernate.impl.SessionImpl.initializeCollection(SessionImpl.java:1743)
at org.hibernate.collection.AbstractPersistentCollection.forceInitialization(AbstractPersistentCollection.java:476)
at org.hibernate.engine.StatefulPersistenceContext.initializeNonLazyCollections(StatefulPersistenceContext.java:867)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:264)
at org.hibernate.loader.Loader.loadEntity(Loader.java:1881)
at org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:71)
at org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:65)
at org.hibernate.persister.entity.AbstractEntityPersister.load(AbstractEntityPersister.java:3072)
at org.hibernate.event.def.DefaultLoadEventListener.loadFromDatasource(DefaultLoadEventListener.java:434)
at org.hibernate.event.def.DefaultLoadEventListener.doLoad(DefaultLoadEventListener.java:415)
at org.hibernate.event.def.DefaultLoadEventListener.load(DefaultLoadEventListener.java:165)
at org.hibernate.event.def.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:223)
at org.hibernate.event.def.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:126)
at org.hibernate.impl.SessionImpl.fireLoad(SessionImpl.java:905)
at org.hibernate.impl.SessionImpl.get(SessionImpl.java:842)
at org.hibernate.impl.SessionImpl.get(SessionImpl.java:835)
at org.hibernate.ejb.AbstractEntityManagerImpl.find(AbstractEntityManagerImpl.java:182)
...................

Jars used in the project are - hibernate-core 3.3.0.SP1.jar and Spring 2.5.6.SEC01.jar
I looked at the code of PersistentBag, and found out that the nullPointer was at line -


This means that session would have been null.
But in my code i see nowhere, where i have closed a session, before this exception is encountered.

Please help with this issue.
Any suggestions would be appreciated.

Thanks.