Via Ovidiu: here is an implementation of the Cocoon Flow layer using java as the flow control language, written by Alex Krut over the weekend.

Looks like the continuation engine used is not Open-Source though. Ovidiu mentions Brakes which as I understand it could be used for java-based continuations as well.

The over the weekend bit says a lot about the modularity of Cocoon, Avalon and about the quality of the current Flow implementation!