[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-4358) Having to use @ForceDiscriminator kind of breaks JPA compatibility

[Karsten Wutzke (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-4358?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=44635#comment-44635 ] 

Karsten Wutzke commented on HHH-4358:
-------------------------------------

Here's what Michael Keith (Author of Pro JPA 2 and member of the JPA expert group) had to say about this:

"The spec does not require an implementation to use discriminator columns to implement JOINED inheritance, however, the assumption is that if @DiscriminatorColumn is specified then it would be used, i.e. the values would be written out. We do not explicitly state that if a @DiscriminatorColumn is specified in the code it must be used, just like we don't explicitly state that if a @Column or @JoinColumn is specified the values must be stored in the table, but there is only so much that we can or should specify. At the lowest level, certain laws of physics and reason are just assumed."

So implementing an option would be the way to go (even though I still believe Hibernate is wrong nontheless). I wonder how existing applications would break if they now set the correct discriminator value instead of the wrong one now... (sorry for turning this into a discussion)

> Having to use @ForceDiscriminator kind of breaks JPA compatibility
> ------------------------------------------------------------------
>
>                 Key: HHH-4358
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-4358
>             Project: Hibernate Core
>          Issue Type: Improvement
>          Components: annotations
>         Environment: JPA
>            Reporter: Steve Ebersole
>            Assignee: Steve Ebersole
>              Labels: jpa2
>             Fix For: 4.0.1
>
>
> According to
> http://opensource.atlassian.com/projects/hibernate/browse/ANN-36
> @ForceDiscriminator was created as a quick workaround to a problem.
> Yes, it solves the problem, but it creates a new problem:
> the source code which previously had only JPA annotations, now need to be annotated by a Hibernate annotation,
> causing that the the source code is now unable to use just any JPA provider.
> Major portability issue!
> Everyone who likes Open Source, hates Lock-Ins!
> My proposal: change the default to a more sane force=true, so that @ForceDiscriminator will not be needed for general JPA projects.
> (And create a @DisableDiscriminator Hibernate annotation, for those who like to brake their code).
> If changing default behavior is risky, don't fix this on older versions, but lets change this from 3.5.0-Beta2.

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