Had an interesting idea I think I might propose to the EJB 3.1 Expert
Group. Wanted to run it by here as I can't seem to think of a good
name for it.
Essentially, many people who want async methods don't actually want
fire and forget. We've already addressed this somewhat with the
ability to return a container controlled java.util.concurrent.Future
instance to the async method caller. It doesn't really address the
parallelization scenario where they want to call several async methods
and wait for them all to complete. Holding onto a handful of Future
objects without the benefit of something like the NIO Selector API
(which is still pretty terrible) is just not going to cut it.
The idea is to introduce something like a @Resynchronize annotation
that could be applied to business methods on the bean class. A
business method or callback with the @Resynchronize annotation would
block until all the all the async methods it calls have completed. So
for example:
@Resynchronize
public void goTeam() {
fooBean.red(); // async method
barBean.green(); // async method
bazBean.blue();
}
At the start of the goTeam() method the container would ready itself
to track async calls. When the bean code calls the red() and green()
methods the container will track those calls and when the goTeam()
method returns to the container, the container will block the thread
till both red() and green() complete. When both are completed, the
container will return control to the caller of goTeam().
Internally if we had something like a CountDownLatch that could count
up as well as down, we'd be set. Any ideas there?
Also, not sure @ Resynchronize is the best annotation name.
-David
