How can I throw an exception within ListeningExecutorService? - guava

Question

I used ListeningExecutorService of guava in my project, got confused about the exception handling.
I used a thread pool, submit a task to it, and set a timeout to the listenableFuture, and add a callback to it.
final ListeningExecutorService threadPool = MoreExecutors.listeningDecorator(Executors.newCachedThreadPool());
Futures.addCallback(listenableFuture, new FutureCallback<**>() {
#Override
public void onSuccess(#Nullable ** data) {
xxxxxxx;
}
public void onFailure(Throwable t) {
xxxxxxxxxx;
if (t instanceof CancellationException) {
throw new QueryException("yyyy");
} else {
throw new QueryException("zzzzz");
}
}
});
I can't catch the exception inside the callback. So I use another ListenableFuture to get the exception
ListenableFuture allFutures = Futures.allAsList(allFuturesList);
try {
allFutures.get();
} catch (CancellationException ce) {
throw new QueryException("");
} catch (InterruptedException t) {
throw new QueryException("");
} catch (ExecutionException e) {
Throwable t = e.getCause();
if (t instanceof QueryException)
throw (QueryException) t;
else
throw new QueryException();
} catch (QueryException qe) {
throw qe;
} catch (Exception e) {
throw new QueryException();
} finally {
}
But I when the callback throw a QueryException, the allFutures can't catch it, allFutures can only catch a CancellationException without the detail error message.
How can I get my detail error message?

Answer 1

Futures.allAsList doesn't do what you expect it to do
From the Javadoc: (emphasis is from me)
Canceling this future will attempt to cancel all the component futures, and if any of the provided futures fails or is canceled, this one is, too.
What you should probably do is create your own aggregating future. You can base your code on Guava's own internal mechanism. See the source code for more info.
Anyways, do not throw exceptions in your FutureCallback::onFailure method.