creating proxies for interfaces with default methods

Jochen Theodorou blackdrag at
Wed May 25 07:22:07 UTC 2016

Hi all,

so in earlier mails to this list I described a bit the problems I got 
into with the way Groovy produces proxies and handles default methods 
for those.

I would like to see how the correct solution to this is supposed to be....

so we have code like m.sortReversed{a,b -> a.value <=> b.value}, where 
sortReversed is getting a Comperator and will call reversed() on it. 
This is not actual API, this is just an example! So far the logic has 
been, that kind of lambda {a,b -> a.value <=> b.value}, is called for 
every non-default, non-static method. If we are talking about functional 
interfaces, there is only one such method. The problem now arises what 
we are supposed to do if a default method is called.

Dynamic proxies and invocation handlers won't do the job, as they do not 
provide an implementation of the interface I can call the default method on.

Which means I have to use LambdaMetaFactory or maybe 
MethodHandleProxies. This may solve the problem...

A second usage is for a kind of mocking. which means we have either a 
map of lambdas, or a lambda which can accept any kind of argument 
constellation...and now multiple non-static, non-default methods to 
proxy. We did use dynamic proxies for that in the past. I do not see how 
that can work with either of the three.

So runtime generated classes is the only option left? Including all the 
problems with class loaders....

bye Jochen

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