From java.util.concurrent.Future<T> to play.libs.F.Promise<T>: How to do that in Java?

Question

I am using play framework to implement a REST API service.

In one function I am using a java async library to talk to another service and it returns a java.util.concurrent.Future<T> that I map (using Guava Futures.transform(~)) into a java.util.concurrent.Future<play.mvc.Result>.

Now, how do I make it a play.libs.F.Promise<Result> so that I can make an AsyncResult?

I found play.libs.Akka.asPromise(scala.concurrent.Future<T> future) but I cannot find a way (in Java) to get a scala future from a java one.

EDIT TEMPORARY SOLUTION: Here is what I am using right now:

Future<T> future = asyncGetTheFuture();
Promise<T> promise = Akka.future(new JFutureToPromise<T>(tempFuture));

with

    class JFutureToPromise<T> implements Callable<T> {
        final Future<T> future;
        final long time;
        final TimeUnit unit;

        private JFutureToPromise(Future<T> future, long time, TimeUnit unit) {
            this.future = future;
            this.time = time;
            this.unit = unit;
        }

        private JFutureToPromise(Future<T> future) {
            this(future, 10L, TimeUnit.SECONDS);
        }

        @Override
        public T call() throws Exception {
            return future.get(time, unit);  
        }
    }

Answer 1

There is no way to non-blockingly/non-pollingly transform an arbitrary j.u.c.Future into an async Future/Promise. Try it and see for yourself :)