What is the best way to handle an ExecutionException?

Question

I have a method that performs some task with a timeout. I use the ExecutorServer.submit() to get a Future object, and then I call future.get() with a timeout. This is workin

Answer 1

The javadoc of java.util.concurrent.Future.get() states the following. Then why not just catch ExecutionException (and Cancellation and Interrupted as declared by the java.util.concurrent.Future.get()) method?

...
Throws:

CancellationException - if the computation was cancelled

ExecutionException - if the computation threw an exception

InterruptedException - if the current thread was interrupted while waiting

So basically you can throw whatever exception within your callable and just catch ExecutionException. Then ExecutionException.getCause() will hold the actual exception your callable threw as stated in the javadoc. This way you are shielded from method signature changes related to checked exception declaration.

By the way you should never catch Throwable, as this would catch also RuntimeExceptions and Errors. Catching Exception is a little bit better but still not recommended, as it will catch RuntimeExceptions.

Something like:

try {  
    MyResult result = myFutureTask.get();
} catch (ExecutionException e) {
    if (errorHandler != null) {
        errorHandler.handleExecutionException(e);
    }
    logger.error(e);
} catch (CancellationException e) {
    if (errorHandler != null) {
        errorHandler.handleCancelationException(e);
    }
    logger.error(e);                
} catch (InterruptedException e) {
    if (errorHandler != null) {
        errorHandler.handleInterruptedException(e);
    }
    logger.error(e);
}