[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-3121) Using fetch="subselect" and second level cache causes NullPointerException

Using fetch="subselect" and second level cache causes NullPointerException -------------------------------------------------------------------------- Key: HHH-3121 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-3121 Project: Hibernate3 Issue Type: Bug Components: caching (L2) Affects Versions: 3.2.6 Environment: Oracle 10g Reporter: Adam Brod I've been tuning some of our mappings to use fetch="subselect" to reduce the number of DB queries. However, I have run into two cases where I get the exception below. In both cases, I was loading a list of Videos, which are mapped to a list of other objects. (In this example, Media is the superclass of Video.) I apologize that I can't upload a full working example, but I will include the relevant mapping info. <class name="Media" table="media" lazy="false" discriminator-value="0"> <cache usage="nonstrict-read-write"/> <id name="id" column="id" type="long"> <generator class="seqhilo"><param name="sequence">hibernate_hi_sequence</param><param name="max_lo">500</param></generator> </id> ... <list name="tags" lazy="true" table="media_tags" cascade="save-update" fetch="subselect"> <cache usage="nonstrict-read-write"/> <key column="media_id"/> <list-index column="idx"/> <many-to-many column="tag_id" class="com.brightcove.catalog.Tag"/> </list> ... <subclass name="Video" lazy="false" discriminator-value="1"> ... </subclass> </class> <class name="Tag" table="tag"> ... </class> The HQL being executed is just a simple "from Video v where v.publisher_id = :pubId". The line of code where the exception is generated in Video.getDTO() is accessing the Tags list: for (Tag tag : getTags()) { tags.add(tag.getDTO()); } I've debugged into the Hibernate source to see where the NPE comes from (CollectionLoadContext line 298). if ( persister.isVersioned() ) { versionComparator = persister.getOwnerEntityPersister().getVersionType().getComparator(); final Object collectionOwner = getLoadContext().getPersistenceContext().getCollectionOwner( lce.getKey(), persister ); version = getLoadContext().getPersistenceContext().getEntry( collectionOwner ).getVersion(); //NPE! } It seems that "collectionOwner" is null, so calling getEntry(collectionOwner) returns null. Calling getVersion() on a null entry is what throws the NPE. java.lang.NullPointerException at org.hibernate.engine.loading.CollectionLoadContext.addCollectionToCache(CollectionLoadContext.java:298) at org.hibernate.engine.loading.CollectionLoadContext.endLoadingCollection(CollectionLoadContext.java:256) at org.hibernate.engine.loading.CollectionLoadContext.endLoadingCollections(CollectionLoadContext.java:222) at org.hibernate.engine.loading.CollectionLoadContext.endLoadingCollections(CollectionLoadContext.java:195) at org.hibernate.loader.Loader.endCollectionLoad(Loader.java:877) at org.hibernate.loader.Loader.initializeEntitiesAndCollections(Loader.java:865) at org.hibernate.loader.Loader.doQuery(Loader.java:729) at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:236) at org.hibernate.loader.Loader.loadCollectionSubselect(Loader.java:2066) at org.hibernate.loader.collection.SubselectCollectionLoader.initialize(SubselectCollectionLoader.java:58) at org.hibernate.persister.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:565) at org.hibernate.event.def.DefaultInitializeCollectionEventListener.onInitializeCollection(DefaultInitializeCollectionEventListener.java:60) at org.hibernate.impl.SessionImpl.initializeCollection(SessionImpl.java:1716) at org.hibernate.collection.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:344) at org.hibernate.collection.AbstractPersistentCollection.read(AbstractPersistentCollection.java:86) at org.hibernate.collection.AbstractPersistentCollection.readSize(AbstractPersistentCollection.java:109) at org.hibernate.collection.PersistentList.size(PersistentList.java:91) at com.brightcove.catalog.EconomicEntity.populateDTO(EconomicEntity.java:460) at com.brightcove.catalog.Media.populateDTO(Media.java:192) at com.brightcove.catalog.Video.populateDTO(Video.java:854) at com.brightcove.catalog.Video.getDTO(Video.java:783) at com.brightcove.catalog.Video.getDTO(Video.java:756)