Andreas Veithen created AXIOM-468:
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Summary: StAXUtils may cause class loader leak
Key: AXIOM-468
URL: https://issues.apache.org/jira/browse/AXIOM-468
Project: Axiom
Issue Type: Bug
Components: API
Affects Versions: 1.2.15
Reporter: Andreas Veithen
Priority: Minor
By default, StAXUtils keep per class loader maps of XMLInputFactory and
XMLOutputFactory instances (where the key is the thread context class loader).
These maps are implemented as WeakHashMap<ClassLoader,XMLInputFactory> and
WeakHashMap<ClassLoader,XMLOutputFactory>. This may cause a class loader leak
if the XMLInputFactory or XMLOutputFactory instance has a strong reference to
the ClassLoader used as key. That case occurs in two scenarios:
1. A StAX implementation is loaded by a class loader that is not the class
loader that loads StAXUtils or one of its parent class loaders, and that class
loader is set as the context class loader when StAXUtils is used. Note that
this is basically the use case for which the per class loader maps were
designed.
2. For whatever reason, the XMLInputFactory/XMLOutputFactory instance keeps a
strong reference to the thread context class loader set when the instance was
created. In that scenario, if StAXUtils is used with a thread context class
loader that is set to any class loader other than the one that loaded StAXUtils
or one of its parents, then StAXUtils will prevent that class loader from being
garbage collected. This type of behavior has been reported for the default StAX
implementation in the Oracle JRE (see
http://markmail.org/message/2kfstgjckrgiimmt). Woodstox is probably not
affected.
The scenario for which the per class loader feature was designed is probably
very rare. As shown above, that scenario is always prone to class loader leaks.
Therefore this feature should probably be removed without replacement, and
StAXUtils should always load the StAX implementation visible to its own class
loader. Note that this mode is already supported, but it is not the default.
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