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https://issues.apache.org/jira/browse/JEXL-246?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16324122#comment-16324122
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Dmitri Blinov commented on JEXL-246:
------------------------------------
As it has turned out for me, Jexl restricts me, for some reason, from
overloading operators in Arithmetic, if the operator signature is of
generalized form, like {{operator(Object)}} or {{operator(Object, Object)}}. So
the idea of having {{public JexlOperator selfAdd(Object x, Object y)}} does not
apply. I don't know if it worth raising an issue about that, or it's better to
find more appropriate the solution to the original problem. Lets not
over-complicate. Suppose, we have an original script for {{z += 1}} and
standard Arithmetic without any {{selfAdd}} overloaded operators. Should this
work for an empty z value? I think it should. So, it should work exactly the
same as with any number of {{selfAdd}} overloaded operators too. It's not an
ambiguity, it's like Jexl couldn't find an appropriate overloaded operator for
this case, and reverted to the default implementation.
> Intermittent ambiguous method invocation when processing assignOverload
> -----------------------------------------------------------------------
>
> Key: JEXL-246
> URL: https://issues.apache.org/jira/browse/JEXL-246
> Project: Commons JEXL
> Issue Type: Bug
> Affects Versions: 3.1
> Reporter: Dmitri Blinov
> Assignee: Henri Biestro
> Priority: Minor
> Fix For: 3.2
>
>
> Sometimes the simple operator like {code}z += 1{code} when {{z}} has not been
> defined yet raises an exception
> {{org.apache.commons.jexl3.internal.introspection.MethodKey$AmbiguousException}}
> with the following stack trace:
> {quote}
> ambiguous method invocation: MyArithmetic.selfAdd(null, java.lang.Integer)
> org.apache.commons.jexl3.internal.introspection.MethodKey$AmbiguousException:
> null
> at
> org.apache.commons.jexl3.internal.introspection.MethodKey$Parameters.getMostSpecific(MethodKey.java:540)
> at
> org.apache.commons.jexl3.internal.introspection.MethodKey$Parameters.access$000(MethodKey.java:452)
> at
> org.apache.commons.jexl3.internal.introspection.MethodKey.getMostSpecificMethod(MethodKey.java:261)
> at
> org.apache.commons.jexl3.internal.introspection.ClassMap.getMethod(ClassMap.java:178)
>
> at
> org.apache.commons.jexl3.internal.introspection.Introspector.getMethod(Introspector.java:146)
> at
> org.apache.commons.jexl3.internal.introspection.MethodExecutor.discover(MethodExecutor.java:52)
> at
> org.apache.commons.jexl3.internal.introspection.Uberspect.getMethod(Uberspect.java:218)
>
> at MyUberspect.getMethod(MyUberspect.java:168)
> at
> org.apache.commons.jexl3.internal.introspection.Uberspect$ArithmeticUberspect.getOperator(Uberspect.java:413)
> at
> org.apache.commons.jexl3.internal.Operators.tryOverload(Operators.java:85)
> at
> org.apache.commons.jexl3.internal.Operators.tryAssignOverload(Operators.java:118)
>
> at
> org.apache.commons.jexl3.internal.Interpreter.executeAssign(Interpreter.java:1292)
>
> at
> org.apache.commons.jexl3.internal.Interpreter.visit(Interpreter.java:1102)
> ....
> {quote}
> The class MyArithmetic contains a couple of overloaded
> {{public JexlOperator selfAdd(T x, Object y)}} methods with the first
> argument being the desired type {{T}} like {{Appendable}} or {{Collection}}
> for which the {{+=}} operator is overloaded.
> Obviously in case where the first argument is null and the second argument is
> an Integer it is not possible to differentiate between {{public JexlOperator
> selfAdd(Collection x, Object y)}} and {{public JexlOperator
> selfAdd(Appendable x, Object y)}} but I wonder is there any point in trying
> to perform {{selfAdd}} on the null variable? What questions me more is that
> this error is intermittent and sometimes there is an exception and sometimes
> there is not, so at the moment I have no test case to reproduce. So I think
> this is a bug.
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