I do not think that the workaround to create a Lookup object by reflection works with 9 given that java.lang.invoke is not declared as an open package.
John Rose has proposed to add a method to get a private Lookup object through sun.misc.Unsafe but as far as i know, this proposal goes nowhere. You can still access to the private constructor of Lookup using defineAnonymousClass. As you may already know, i've developed the Proxy2 library [1], exactly for that (and to be far more efficient than a java.lang.reflect.Proxy). regards, Rémi [1] https://github.com/forax/proxy2 ----- Mail original ----- > De: "Matthew Hall" <qualidaf...@gmail.com> > À: jigsaw-dev@openjdk.java.net > Envoyé: Mardi 3 Janvier 2017 04:28:09 > Objet: Invoking default methods from a Proxy's InvocationHandler in JDK9 > I'm a member of the JDBI [1] project, an open source SQL access library > atop JDBC. > > A major part of our API provides implementations of declarative interfaces > defined by users (similar to MyBatis). Interface methods may be default (in > which case the default method implementation is used) or abstract (in which > case JDBI provides the implementation). > > We're using JDK 8, and we use java.lang.reflect.Proxy and InvocationHandler > to provide declarative interface implementations for our users. > > Prior to release of JDK 8, it appears that the subject of enhancing Proxies > for default methods was discussed [2], but ultimately did not make it into > the release. > > The root of the problem is that the generated Proxy class overrides all > methods in the proxy interfaces. This means that the interface default > methods are now superclass methods to the proxy class, which makes them > un-invokable from outside code--including the InvocationHandler. > > As far as we can tell, the _only_ way to invoke a default method--on a > proxy, from an InvocationHandler--is to resort to some horrible > setAccessible shenanigans [3]. > > Specifically, we have to: > 1. Call Constructor.setAccessible(true) to make the private constructor > MethodHandles.Lookup(Class<?> lookupClass, int allowedModes) accessible, > 2. Invoke that private constructor to instantiate a MethodHandles.Lookup > with private (!) access to all the things, > 3. Call Lookup.unreflectSpecial to get the MethodHandle for the default > method, and > 4. Invoke the method through the MethodHandle. > > This is ugly, but it works--for now. If JDK 9 takes away access to > setAccessible, it may cease to work. > > I found some discussion about this last summer [4], but it's hard to tell > if anything came out of the discussion. > > Is there anything on the roadmap for JDK9 to allow a proxy's > InvocationHandler to invoke default methods on proxies? Are there any > existing proposals I should be aware of? > > Regards, > > Matthew Hall > > [1] https://github.com/jdbi/jdbi/ > [2] > http://mail.openjdk.java.net/pipermail/lambda-dev/2012-August/005675.html > [3] > https://github.com/jdbi/jdbi/blob/jdbi3/sqlobject/src/main/java/org/jdbi/v3/sqlobject/DefaultMethodHandler.java > [4] > http://jigsaw-dev.1059479.n5.nabble.com/creating-proxies-for-interfaces-with-default-methods-td5711955.html
