Cancelling a server-side GWT call

Question

I'm using RequestBuilder to time out GWT requests which take too long:

RequestBuilder requestBuilder = _service.getStatistics(callback);
requestBuilder.setTimeoutMillis(5000);
try {
    requestBuilder.send();
} catch (RequestException e) {
    GWT.getUncaughtExceptionHandler().onUncaughtException(e);
}

Is there a way of notifying the invoked remote service that the call has timeout out on the client and that it should be cancelled?

Answer 1

Not unless you make another call to tell the remote service that the previous call was cancelled!

Answer 2

This actually depends. If the server is doing a lot of work (and you are not on Google App Engine) you can keep the Request around and call request.cancel(). This will end the browser's request, but the server will keep working.

Depending on the format of the data you are returning, you can have the server flush some empty data to the client periodically while the call is processessing. This will cause the flush to throw an IOException if the client has cancelled the request and the HTTP connection is terminated. You can then catch this request and stop processessing the request on the server side.