[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-1621) subclass mapping by discriminator - should instantiate parent for unmapped discriminator values

[Felipe Zschornack (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-1621?page=comments#action_24637 ] 

Felipe Zschornack commented on HHH-1621:
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I have the same problem. The select clause generated by Hibernate not consider the discriminator column (this column is not part of the 'where' part of the select). 

When Hibernate try to get the discriminator value, a erroneous key is used (in my case, instead of discriminator key, the primary key was used), so 
so the 'get' method of the subclassesByDiscriminatorValue HashMap

       subclassesByDiscriminatorValue.get(value); (SingleTableEntityPersister.java:431)

will return 'null' instead of the correct discriminator value. This occurs in 

final String result = persister.getSubclassForDiscriminatorValue( discriminatorValue ); (Loader.java:1441)

> subclass mapping by discriminator - should instantiate parent for unmapped discriminator values
> -----------------------------------------------------------------------------------------------
>
>          Key: HHH-1621
>          URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-1621
>      Project: Hibernate3
>         Type: Improvement

>   Components: core
>  Environment: 3.1.2
> Sybase ASE 12.5.3
>     Reporter: Martin Schulz
>  Attachments: HHH-1621
>
>
> Scenario:  The parent class A has a discriminator field and some but all possible scriminator values are mapped to subclasses.
> Current behavior:
> 1) Default:
> The following exception is thrown
> org.hibernate.WrongClassException: Object with id: 10000 was not of the specified subclass: A (Discriminator: D)
> 	at org.hibernate.loader.Loader.getInstanceClass(Loader.java:1445)
> [ the error itself is also quite misleading, as the row is exactly of / for the specified class A. But there simply was no
>   subclass found ].
> 2) discriminator with force="true"
> The parent class is never instantiated, only the mapped subclasses are instantiated.
> Proposed behavior:
> The parent class should be instantiated for those rows with unmapped discriminator values.
> Characteristics of proposed behavior:
> - all rows in resultset would lead to instantiated class in the inheritence tree,
> - the behavior would be in line with how joined-subclass behaves
> - no caveat documentation required
> Implementation:
> (Easy)
> in Loader.java, lines 1443ff, do not throw WrongClassException, but instead 
> return persister.getEntityName();
> (Alternate)
> change persister.getSubclassForDiscriminatorValue() implementations correspondingly.
> Thx for your consideration / vote.

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