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From "Kevan Miller (JIRA)" <j...@apache.org>
Subject [jira] Created: (GERONIMO-4957) javax.el.CompositeELResolver is not thread-safe
Date Wed, 18 Nov 2009 16:38:39 GMT
javax.el.CompositeELResolver is not thread-safe
-----------------------------------------------

                 Key: GERONIMO-4957
                 URL: https://issues.apache.org/jira/browse/GERONIMO-4957
             Project: Geronimo
          Issue Type: Bug
      Security Level: public (Regular issues)
          Components: specs
    Affects Versions: 2.1.4, 2.1.5, 2.2, 2.2.1, 3.0
            Reporter: Kevan Miller


A user reported that they get an intermittent NullPointerException:

17:08:45,133 ERROR [[jsp]] Servlet.service() for servlet jsp threw exception
java.lang.NullPointerException
at javax.el.CompositeELResolver.getValue(CompositeELResolver.java:53)
at org.apache.myfaces.el.unified.resolver.FacesCompositeELResolver.access$301(FacesCompositeELResolver.java:46)
at org.apache.myfaces.el.unified.resolver.FacesCompositeELResolver$4.invoke(FacesCompositeELResolver.java:108)
at org.apache.myfaces.el.unified.resolver.FacesCompositeELResolver.invoke(FacesCompositeELResolver.java:148)
at org.apache.myfaces.el.unified.resolver.FacesCompositeELResolver.getValue(FacesCompositeELResolver.java:104)
at javax.el.CompositeELResolver.getValue(CompositeELResolver.java:53)
at org.apache.el.parser.AstIdentifier.getValue(AstIdentifier.java:61)
at org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:186)
at org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate(PageContextImpl.java:925)
...

The only way I can explain this exception is that multiple threads are simultaneously invoking
add() (and the resolvers[] array is becoming corrupted). Or multiple threads are simultaneously
accessing add() and getValue() (and getValue() is accessing an uninitialized array element).


The EL spec is silent on thread-safety issues for CompositeELResolver (though it does identify
thread safety issues for some other classes). I don't see anything spec-wise that prevents
multi-threaded access to CompositeELResolver. If anyone has other opinions, let me know. Otherwise,
looks like we need to close some timing windows in CompositeELResolver.

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