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Andrea,
On 9/29/2009 4:34 AM, aaime74 wrote:
> I can cleanly stop the rendering process in almost any point of it.
> The issue is not stopping it, it's detecting the client connection
> was dropped.
>
> No matter what solution is adopted, one still depends on the ability
> to detect the client has dropped the connection, something that no
> one so far described how to check (I'm starting to wonder if there
> is a way at all).
I would do something like this, adopting Jason's strategy:
private static final byte[] NOTHING = new byte[0];
public void doGet(...) { // or whatever
OutputStream out = response.getOutputStream();
// look into java.util.concurrent.Executor and friends if
// you've never seen them... great stuff
MapDrawingTask /* implements Callable */ task = new MapDrawingTask();
Future<Void> task = executor.submit(task);
while(!task.isDone() && !task.isCancelled()) {
try {
Thread.currentThread().sleep(100); // or whatever timeout you want
}
catch (InterruptedException ie) {
// Ignore
}
try {
out.write(NOTHING);
out.flush();
}
catch (ClientAbortException cae) {
task.cancel(true); // allow interruptions
// the "break" isn't strictly necessary
break; // or even "return" if you want to get out quick
}
}
if(!task.isCancelled()) {
// dump output to response
}
}
You may want to catch more exceptions than just ClientAbortException
there, you might need more error handling in general, and my
quick-and-dirty thread-and-task management will probably need some
improvement and cleanup, but you get the general idea: the HTTP thread
blocks waiting for either the map-drawing task to complete, or for the
client to hang up the phone.
Hope that helps,
- -chris
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