[jira] [Commented] (OPENJPA-2507) Weird EmptyStackException in CriteriaQueryImpl

["Oliver Gierke (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/OPENJPA-2507?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14016290#comment-14016290 ] 

Oliver Gierke commented on OPENJPA-2507:
----------------------------------------

Just to confirm this: Spring Data JPA is caching {{CriteriaQuery}} instances as in contrast to {{EntityManager}} and {{EntityManagerFactory}} there's no hint in the spec about the {{CriteriaQuery}} instances to be allowed to not be thread safe, once constructed and equipped with predicates.

> Weird EmptyStackException in CriteriaQueryImpl
> ----------------------------------------------
>
>                 Key: OPENJPA-2507
>                 URL: https://issues.apache.org/jira/browse/OPENJPA-2507
>             Project: OpenJPA
>          Issue Type: Bug
>          Components: criteria
>    Affects Versions: 2.2.0, 2.3.0
>         Environment: openjpa 2.2.0 & 2.3.0, spring-data-jpa up to 1.4.2
>            Reporter: Ioannis Alexandrakis
>            Priority: Minor
>              Labels: criteria_api, openjpa
>
> Using spring-data-jpa with openjpa, I sometimes encounter a strange error (not all the times, but under heavy load it makes its appearance, sparsely though):
> ....
> Caused by: java.util.EmptyStackException
>         at java.util.Stack.peek(Stack.java:<arbitrary line>)
>         at org.apache.openjpa.persistence.criteria.CriteriaQueryImpl.ctx(CriteriaQueryImpl.java:<arbitrary line>
> ....
> I do not know which behaviour triggers it, however I think it would be an improvement to change (I did not know where exactly to file it, because it is both an improvement and a bug in my opinion), in org.apache.openjpa.persistence.criteria.CriteriaQueryImpl, method: Context ctx(), this:
> return _contexts == null || _contexts.isEmpty() ? null :  _contexts.peek();
> to something like this:
> try {
> 	return _contexts == null || _contexts.isEmpty() ? null :  _contexts.peek();
> } catch (EmptyStackException e) {
>     return null;
> }
> , in order to prevent a case where multiple threads modify the "_contexts" between the evaluation of the inline "if".
> I am not able to reproduce it all the time, thus I can't create a useful test, neither have I created a patch due to the simplicity of the 'fix'. However I believe it is a harmless fix which could be considered a minor improvement.



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