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https://issues.apache.org/jira/browse/OPENJPA-1804?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12912984#action_12912984
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Willis Blackburn commented on OPENJPA-1804:
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Rick, you asked, "Perhaps we need to have a stronger warning message when this
feature is enabled? ... or disable it all together?"
I saw on the roadmap that OpenJPA 2.1 will require Java 6. I think that if
OpenJPA is not going to support Java 6, then there is no need to support
working with unenhanced classes. The strategy of using the attach API to
install the agent will work for casual users, and the others can pass the agent
on the command line, use the J2EE container hooks, or use the build-time
enhancer. The behavior of OpenJPA when using unenhanced classes is different
from its behavior when using enhanced classes (no lazy loading, changes only
detected at flush), so anything that users actually develop in that mode is not
going to be production-ready. At some point developers will have to figure out
how to get the agent or the build-time enhancer working and test their code
under that configuration. Given how easy it is to use the attach API enhancer
under Java 6, there's not a strong case for having a less-functional
alternative.
Have I added enough comments to this issue yet? I think I'm going for a
personal record.
> NPE in MappingInfo.java line 1514
> ---------------------------------
>
> Key: OPENJPA-1804
> URL: https://issues.apache.org/jira/browse/OPENJPA-1804
> Project: OpenJPA
> Issue Type: Bug
> Components: Enhance, UnenhancedClasses, usability
> Affects Versions: 2.0.1
> Reporter: Willis Blackburn
>
> I am encountering a NPE at MappingInfo.java line 1514. I'm sorry I don't
> have time to prepare a test case right now. I'm not even 100% sure what is
> causing the problem, but it seems to be something like this:
> I have classes Organization, Group, User, and AddressBook.
> Group has a reference (many-to-one) to Organization.
> I'm using field-level access and the Java 6 runtime enhancer. (NOT the
> build-time enhancer or the agent.)
> In ManagedClassSubclasser.prepareUnenhancedClasses, the code receives a list
> of Class objects--the ones in persistence.xml. They are not in the same
> order as they are in persistence.xml, but I don't know if that's important.
> The first one is Group. During the processing of Group, the code invokes
> ClassMapping.setTable to set the table name, which is "group_table." This
> comes from the @Table annotation of Group. So far, so good. Then the code
> does some additional processing on the relationship mappings of Group, which
> include the reference to Organization. During the processing of that
> relationship, the code calls MappingInfo.mergeJoinColumn. On line 1367, the
> method calls rel.getTable. The "rel" variable points to the ClassMapping for
> Organization. Remember that prepareUnenhancedClasses hasn't gotten to
> Organization yet--it's still working on Group--and so I assume that this
> Organization mapping was created on-demand. However, rel.getTable returns
> null. The Organization class has a @Table attribute, and I can see that the
> table name has been loaded in the ClassMappingInfo instance attached to the
> ClassMapping for Organization, however the table name has not yet been copied
> from ClassMappingInfo to ClassMapping. Later, the mergeJoinColumn method
> attempts to dereference the null table name and generates the NPE.
> Bottom line: When using the Java 6, runtime enhancer, if class A has a
> reference to class B, and both classes have @Table annotations (at least),
> and class A is processed first, then it produces a NPE.
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