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

[Steve Ebersole (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-3121?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=39684#action_39684 ] 

Steve Ebersole commented on HHH-3121:
-------------------------------------

I can reproduce the exception Samuel sees with his attached test case.  The problem is that his test case is very different from the situation described here.  The only real commonality is that they trigger an exception in the same piece of code.

However, I have tried now for about 2 hours and am not able to reproduce the actual reported problem.  So the description is missing something vital I need to reproduce this.

At this point I am going to split Sammuel's test out into a separate issue with his test case and work on that since I can at least reproduce it.  I'll set this one back to awaiting a test case to move forward.

> Using fetch="subselect" and second level cache causes NullPointerException
> --------------------------------------------------------------------------
>
>                 Key: HHH-3121
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-3121
>             Project: Hibernate Core
>          Issue Type: Bug
>          Components: caching (L2)
>    Affects Versions: 3.2.6
>         Environment: Oracle 10g
>            Reporter: Adam Brod
>            Assignee: Steve Ebersole
>             Fix For: 3.6.1
>
>         Attachments: CollectionIssue_TestProgram.zip
>
>
> 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)

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