[GERONIMO-4957] javax.el.CompositeELResolver is not thread-safe

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.1.4, 2.1.5, 2.2, 2.2.1, 3.0.0
• Fix Version/s: 2.1.5, 2.2.1
• Component/s: specs
• Security Level: public (Regular issues)
• Assignee: Kevan Lee Miller
• Reporter: Kevan Lee Miller
• Created: 18/Nov/09 16:37
• Updated: 25/Mar/10 01:02
• Resolved: 25/Mar/10 01:02

Description

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.