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https://issues.apache.org/jira/browse/OPENJPA-2699?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16050828#comment-16050828
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Jody Grassel commented on OPENJPA-2699:
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The original problem was that a deadlock could occur in an Enterprise
environment (WebSphere in particular) when two concurrent threads are loading a
class which triggers a transformer, where there are two classloaders with one a
child of the other. The deadlock would occur when OpenJPA initialized the
saxparser, which searches for parser impls using the thread context
classloader, which happened to be the leaf classloader in that scenario. The
solution was to temporally override the thread context classloader when
initializing the xml parser to the classloader used to load openjpa, avoiding
that problem.
When I first introduced the fix, I shipped it as disabled (think in 2.0.x or
2.1.x) by default (needing to be enabled manually), but shipped it as enabled
in trunk and in 2.2.x. Because the configuration wasn't directly accessible in
the place where the temp override needed to occur, there was a bit of a
convoluted means to set that variable to match the configuration. I suspect
that there is an alternate path that reaches the xml parser initialization
point that misses pulling that value from configuration.
But, in 2.2.x and trunk, it should have been set to true (the default) anyways,
and I must have missed setting that value when I delivered the update to enable
it by default in 2.2.x.
So I am fine with the change, it's the one I was recommending to resolve the
problem anyways.
> Occasional deadlock initializing the XML Parser
> -----------------------------------------------
>
> Key: OPENJPA-2699
> URL: https://issues.apache.org/jira/browse/OPENJPA-2699
> Project: OpenJPA
> Issue Type: Bug
> Components: jpa
> Affects Versions: 2.2.2
> Reporter: Will Dazey
> Priority: Minor
> Labels: easyfix
> Fix For: 2.2.2
>
> Attachments: OPENJPA-2699-2.2.x.patch
>
>
> This change was missed during OPENJPA-1993
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