Converting MethodHandle into reflective Method instance

[Eric Bodden]

Hi again.

> Yes. :-) MutableCallSites (which are specified in the java.lang.invoke
> APIs) support setTarget() to set the callsite's target, and there are a
> set of methods on java.lang.invoke.MethodHandles for combining method
> handles in various ways. I would expect almost all language
> implementations using method handles would make quite heavy use of those
> APIs, and most will bootstrap to a call site with some sort of fallback
> target and change that target on the first invocation to a guardWithTest.

Ok, now I see what you mean. Thanks for the clarification.

>
>>> I think your only real option is intercept the calls that get the method
>>> handles in the first place, so you'd need to transform most calls to
>>> Lookup objects and unreflect(). That shouldn't be too hard a bit of code
>>> transformation to do.
>>
>>That's a good idea which we can try. Unfortunately it will require
>>modifications to the JDK. That's something I was trying to avoid.
>
> Could you not do this by transforming the code outside the JDK that calls
> those methods? I assume you have to do something similar to existing code
> which uses reflection to avoid it bypassing your advice-execution code.

True, this should work as well. Sort of like a "call-pointcut" in
AspectJ terms. Reflection is actually another interesting topic.
Currently it is not yet handled either.

> Oh, and I've just realised you'll also have to do something about any
> MethodHandles that have been compiled into a classes constant pool as
> well. Some of those will be the bootstrap methods for invokeDynamic
> instructions, but other things could have been stuffed in their.

Hmmm, good point. I had forgotten about those, too. Good thing that
those are all static.

Cheers,
Eric