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https://issues.apache.org/jira/browse/OPENJPA-2817?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17156804#comment-17156804
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Jody Grassel commented on OPENJPA-2817:
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Pull request for 2.2.x branch:
https://github.com/jgrassel/openjpa/pull/new/OPENJPA_2817_22X
> OpenJPA enhancer needs improved reentrancy
> ------------------------------------------
>
> Key: OPENJPA-2817
> URL: https://issues.apache.org/jira/browse/OPENJPA-2817
> Project: OpenJPA
> Issue Type: Bug
> Components: Enhance
> Affects Versions: 2.2.2, 2.3.0, 2.4.3, 3.1.1
> Reporter: Jody Grassel
> Assignee: Jody Grassel
> Priority: Major
>
> OpenJPA's class transformer was designed in a time when ClassLoader access
> was synchronized. Because it was assumed that if the ClassLoader caused
> another class to load while it was already enhancing a class, causing another
> triggering of the class transformer, it was assumed that that could only
> happen if OpenJPA was bundled as part of the application (loaded by the app
> classloader in an EE environment), and was safe to assume that this reentrant
> invocation would not be a request to enhance a persistent type, and thus
> return null (no enhancement needed).
> With Java 7+, ClassLoader locking has been changed
> ([https://docs.oracle.com/javase/7/docs/technotes/guides/lang/cl-mt.html]).
> Now, because the same ClassLoader (and thus same transformer), can be invoked
> concurrently by different threads, this assumption was no longer valid.
> OpenJPA needs to be updated to be mindful of reentrancy on a thread scope,
> instead of just simply reacting to reentrancy whenever it happens.
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