Proposal: java.lang.reflect.Proxy and default methods

[Jake Wharton]

On Fri, Jun 3, 2016 at 10:58 AM Peter Levart <peter.levart at gmail.com> wrote:

> InvocationHandler gets invoked for default methods, but it
> has not provision to forward such calls to the default implementations
> in the interfaces.
>

This isn't quite true. You can use MethodHandles to invoke the default
method if the interface is public:

    Object returnValue = MethodHandles.lookup()
        .in(declaringClass)
        .unreflectSpecial(method, declaringClass)
        .bindTo(proxy)
        .invokeWithArguments(args);

If the interface is not public, things get a bit more tricky since you need
an instance which ignores the visibility. The only way to get at this is
through creating your own trusted instance for the interface type:

    Constructor<Lookup> constructor =
        Lookup.class.getDeclaredConstructor(Class.class, int.class);
    constructor.setAccessible(true);
    Object returnValue = constructor.newInstance(declaringClass, -1 /*
trusted */)
        .unreflectSpecial(method, declaringClass)
        .bindTo(proxy)
        .invokeWithArguments(args);

That said, I'm all for an API that makes this easier! Please make sure it
handles non-public interface types as well.