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https://issues.apache.org/jira/browse/CAY-2667?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17465015#comment-17465015
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Nikita Timofeev commented on CAY-2667:
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Hi [~mattraydub], thanks for the reminder!
I looked your PR some time ago, unfortunately not as much as I wanted.
I found two things that stop me from applying it to the 4.2 branch.
# there's incompatible method changes, this is rather technical and I could fix
it on my own
# I can feel that there could be some performance issues, but I don't have time
to test everything thoroughly, and that's a bigger problem for now.
Once we branch out 4.2 (and I think we could do it already) I wanted to apply
your PR to the next version (4.3?) so it could be tested safely.
> Fix Issues with Generic Vertical Inheritance
> --------------------------------------------
>
> Key: CAY-2667
> URL: https://issues.apache.org/jira/browse/CAY-2667
> Project: Cayenne
> Issue Type: Bug
> Components: Core Library
> Reporter: Matt Watson
> Priority: Major
> Labels: Generic, inheritance, vertical
> Fix For: 4.2.B2
>
> Time Spent: 0.5h
> Remaining Estimate: 0h
>
> I discovered a couple issues when trying to implement Vertical Inheritance
> using Generic Persistent Classes (Java-less)
> *The 1st issue* is that one of the Subclasses will get the wrong Qualifier
> assigned because the wrong ObjEntity is returned during
> BaseContext.injectInitialValue because the
> MappingCache.objEntitiesByClassName is keyed by class-name so it can only
> hold one of the possible many generic ObjEntities.
> See Test and DataMap implementing a Generic Student that has sub Entities of
> a Generic Boy and a Generic Girl.
> It inserts 2 records into [gen_student], 1 record into [gen_boy], 1 record
> into [gen_girl], but the [type] on both student records is "G", instead of
> one "B" and one "G".
> When creating the GenBoy ... the line:
> getEntityResolver().getObjEntity(object.getClass()) its returning the "Girl"
> ObjEntity
> the MappingCache.objEntitiesByClassName holds an entry for
> "CayenneDataObject" with value for Girl ObjEntity. When using Generics there
> will be many ObjEntities that use CayenneDataObject, so we shouldn't be
> asking for it from this cache Map.
> instead we should use: getEntityResolver().getObjEntity((Persistent)object)
> because that one is properly getting the correct ObjEntity from the ObjectId,
> in MappingCache.getObjEntity(Persistent object)
> *The 2nd issue* is that when querying for GenStudents, it returns the correct
> records, but only the Girl is populated and the Boy is HOLLOW, because the
> query generated does not do a left join to gen_boy.
> {code:java}
> ObjectSelect.query(DataObject.class, "GenStudent").select(context);
> {code}
> This happens because PersistentDescriptor.subclassDescriptors is a map keyed
> by a class name, so the 2nd one overwrites the first one. This map should be
> keyed by the ObjEntity name to support Generic Persistent Classes.
> There is a test included that will show that with my fixes the
> PersistentDescriptor.subclassDescriptors now can hold the 2 ClassDescriptors
> for the 2 generic Sub ObjEntities.
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