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https://issues.apache.org/jira/browse/OPENJPA-1978?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13029290#comment-13029290
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Sascha Just commented on OPENJPA-1978:
--------------------------------------
Thanks for your reply Rick.
Changing the targetEntity does indeed solve the problem (at least for the test
case I submitted). I can't test this on the productive code since we changed
the model of this module and switched to a InheritanceType.JOINED strategy.
Your suggestion works in both scenarios:
private A a;
@ManyToOne (cascade = CascadeType.ALL, fetch = FetchType.LAZY, targetEntity =
A.class)
public A getA() {
return this.a;
}
and
private B a;
@ManyToOne (cascade = CascadeType.ALL, fetch = FetchType.LAZY, targetEntity =
B.class)
public B getA() {
return this.a;
}
I actually can't remember why we set the targetEntity to the superclass in the
first place.
Anyways, OpenJPA is pretty good with error handling and should throw a
non-fatal user exception (containing an appropriate error message) instead of
crashing with a NullPointerException if the targetEntity points to the abstract
superclass and the return type is a (non-abstract) subclass of the targetEntity.
> Using a MappedSuperclass with IdClass causes NullPointerException in OpenJPA
> when having classes with persistent fields of the superclass type.
> ------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: OPENJPA-1978
> URL: https://issues.apache.org/jira/browse/OPENJPA-1978
> Project: OpenJPA
> Issue Type: Bug
> Affects Versions: 2.1.0
> Environment: independent, tested on Mac OS X (10.5/10.6) and Linux
> 2.6.32
> Reporter: Sascha Just
> Attachments: openjpa-nullpointerexception.tar.gz, stacktrace.txt
>
>
> We got a MappedSuperclass A with IdClass APK. The class B extends A using
> inheritance type 'TAPE_PER_CLASS'.
> The class C holds a field of type A. OpenJPA crashes with a
> NullPointerException in org.apache.openjpa.jdbc.meta.MappingInfo#mergeColumn.
> We tried different annotation strategies to tackle this problem but didn't
> find a way to get rid of the NullPointerException. While looking at the bug
> database we found a lot of issues that might be related to this problem but
> weren't able to track down the cause of the error.
> I will attach a stacktrace and a maven project containing a testcase for the
> above scenario reproducing the error.
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