invoking a interface default method from within an InvocationHandler

[Remi Forax]

On 10/20/2014 11:25 AM, Cédric Champeau wrote:
> For what it's worth, in Groovy, we have two separate pathes to 
> "implement classes at runtime", that is to say generating proxies. In 
> the case of an interface, we rely on the JDK proxy just because it is 
> *much* faster than generating a class through ASM. I mean that 
> generating a class in ASM is orders of magnitude slower (at least in 
> our case) than relying on the JDK proxy adapters. Of course, it then 
> depends on how often the method is called, because at some point a 
> generated class will be faster, but so far, the choice we made is 
> better in practice, because lots of people do not realize that if they 
> do "foo as SomeInterface" in a loop, they are generating a new proxy 
> for each call...

I've just taken a look to the code of j.l.r.Proxy, 
(sun.misc.ProxyGenerator), and I don't understand how ASM can be an 
order of magnitude slower, if you just look to how the code is 
generated. So I suppose that it's because j.l.r.Proxy use it's own 
defineClass() method instead of the one in ClassLoader, and that this 
defineClass() avoid to spend time to do things like class verification.

Rémi

>
> 2014-10-20 11:19 GMT+02:00 Paul Sandoz <paul.sandoz at oracle.com 
> <mailto:paul.sandoz at oracle.com>>:
>
>
>     On Oct 18, 2014, at 6:59 PM, Peter Levart <peter.levart at gmail.com
>     <mailto:peter.levart at gmail.com>> wrote:
>     >
>     > Hi Paul, Remi,
>     >
>     > The complete solution will require new API, but the
>     java.lang.reflect.Proxy API could be improved a bit too. With
>     introduction of default interface methods it is somehow broken
>     now. Default interface methods enable interface evolution, but
>     break existing Proxy InvocationHandler(s) which are not prepared
>     to handle new methods. So perhaps a small improvement to Proxz API
>     could be to add new factory method that takes an additional a
>     boolean flag indicating whether generated proxy should override
>     default methods and forward their invocation to InvocationHandler
>     or not. An all-or-nothing approach. I know that even that is not
>     trivial. Generated proxy class can implement multiple interfaces
>     and there can be conflicts. In that case, the easiest solution is
>     to bail out and refuse to generate a proxy class with such
>     combination of interfaces.
>
>     It would also be useful to investigate a safe mechanism so that an
>     InvocationHandler implementation can call a default method, which
>     then allows an impl to explicitly deal with conflicts.
>
>
>     >
>     > A starting point could be to re-implement current functionality
>     using ASM and then start experimenting with different approaches.
>     What do you think?
>     >
>
>     Not sure replacing the bytecode generating implementation, in
>     sun.misc.ProxyGenerator, with an ASM equivalent will really help
>     all that much functionality wise, that may be nice from a
>     unification perspective but does introduce some risk. A quicker
>     route might be to work out how to filter out the default methods
>     that are overridden in the existing code.
>
>     Paul.
>
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