I am attempting to get Janino 2.6.1 working with Logback 0.9.28 (or later, but
that's the version we are using in Eclipse Virgo right now) - see [0] for
background. Unfortunately Janino ends up using the thread context class loader
as its "parent" class loader and fails with a runtime exception. I have
discussed this ([1]) on the Janino mailing list and it seems that it is
necessary to set the parent class loader in Janino. I am somewhat at the mercy
of Logback here.
The surprising thing is that the code in Logback 0.9.24 looked pretty usable in
this respect. JaninoEventEvaluator.start had the following sequence:
ClassLoader cl = context.getClass().getClassLoader();
ee = new ExpressionEvaluator(getDecoratedExpression(), EXPRESSION_TYPE,
getParameterNames(), getParameterTypes(), THROWN_EXCEPTIONS, cl);
thus setting the parent class loader to a value which I could ensure would be
capable of loading the necessary types.
In 0.9.28 this code has been replaced by:
scriptEvaluator = new ScriptEvaluator(getDecoratedExpression(),
EXPRESSION_TYPE,
getParameterNames(), getParameterTypes(), THROWN_EXCEPTIONS);
which causes the current TCCL to be used as the parent class loader and
ultimately results in Janino failing.
I can't control the TCCL that happens to be in use when start is called as that
is driven out of a logging call which can come from an arbitrary thread.
I found the relevant commit ([2]), but I can't tell from that why this specific
change was made.
If it is absolutely necessary to use ScriptEvaluator rather than
ExpressionEvaluator, the following code sequence (based on a suggestion from
Arno Unkrig) would reproduce the parent class loader behaviour of 0.9.24:
ClassLoader cl = context.getClass().getClassLoader();
scriptEvaluator = new ScriptEvaluator();
scriptEvaluator.setParentClassLoader(cl);
scriptEvaluator.setReturnType(EXPRESSION_TYPE);
scriptEvaluator.setParameterNames(getParameterNames());
scriptEvaluator.setParameterTypes(getParameterTypes());
scriptEvaluator.setThrownExceptions(THROWN_EXCEPTIONS);
scriptEvaluator.cook(getDecoratedExpression());
The alternative of using ExpressionEvaluator is much neater and seems to be
close to the ScriptEvaluator variant since ExpressionEvaluator extends
ScriptEvaluator.
Any suggestions gratefully received.
Regards,
Glyn
[0] https://bugs.eclipse.org/bugs/show_bug.cgi?id=333920
[1] mailing list archive link currently broken - if I can get a link to it,
I'll post this later
[2]
https://github.com/ceki/logback/commit/06a5b692f14560636bd92d7bd7cf1f85830f4e55#diff-4
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