On 10.01.2017 12:28, Uwe Schindler wrote:
Hi,
just coming to the example you brought, because I exercised this a week ago:
[...] For example... can you
call Object#clone on Object using MethodHandles? I actually did not try
this, but since the method is protected and in a module I would assume
no. You had been able to do so by reflection. Let us not discuss about
if that makes sense or not. It just shows for me that (ii) is simply not
there.
Hi, it is impossible to call Object#clone with MethodHandles. Not even in the same module
unless you unreflect an accessible reflective method. I tried something similar last week
to fix the Cglib issues with invoking protected ClassLoader#defineClass. The idea was
"the standard MethodHandle" trick:
Create an abstract subclass of ClassLoader - just to have a static initialization block.
In this static block you get a (private) Lookup object to lookup the protected
defineClass method. Which works phantastically! As it is virtual, the MethodHandle should
now allow to call the method with any ClassLoader as first parameter (the receiver of
virtual method). This works for all methods, but not protected ones. If you read the
Javadocs it is in the specs. For protected methods, the methodhandle is
"modified" and the receiver argument is casted to the Lookup's class. And
because of this you get a ClassCastException if you don't call with a receiver that is
assignable to the current Lookup's class.
Too stupid, the designers of MethodHandles were way too intelligent :-)
See my investigations:
https://github.com/cglib/cglib/issues/93#issuecomment-269255311
I guess the trick is that I am using reflection to get a Lookup object
that has full priviledges... a trick that does no longer work in current
jigsaw
bye Jochen
