Question

I have two requests in tomcat. One HTTP request will create a thread. Client can use a new HTTP request to terminate the same thread.

Is it possible to do that? If possible how?

Answer 1

Oh please, don’t spawn unmanaged threads yourself in a Java EE application. Use an Executor with a fixed thread pool. Use Callable as tasks and use Future as future results.

Create one on application’s startup (e.g. in ServletContextListener or servlet’s init()).

ExecutorService executor = Executors.newFixedThreadPool(10); // Pool of 10 threads.

On first request, submit a task to it, get the Future result. The below example assumes that it’s of type String and that Task is a Callable<String>:

Future<String> result = executor.submit(new Task());

Store this in the session:

request.getSession().setAttribute("result", result);

On any subsequent request in the same session, you could get it from the session and check if it’s done or not and if necessary cancel it.

Future<String> result = (Future<String>) request.getSession().getAttribute("result");

if (result != null) {
    if (!result.isDone() && userWantsToCancel) {
        result.cancel();
    }
}

See also:

• Java concurrency tutorial