带有Jersey和Tomcat的Java Web Services。 ¿当Web服务停止时如何停止所有线程？

Question

I need some kind of help to see the way to solve this problem.

I have a java webservice using jersey in a tomcat server. My java code launches some threads for some tasks. All works fine. The problem is that when the webservice is stopped on the manager panel of the tomcat server, the threads continue his execution.

Exists a way to stop all the threads of this kind of java jersey webservice when the user press the Stop button on the manager panel of the tomcat server?

Thanks

PD: i know that exists a interrupt() function for the threads in java, but i dont know how to launch that function when the user press the stop button in the manager panel of the server.

Answer 1

You can try setting the threads to deamon mode. You can use the method setDaemon() within Thread to do this. The Java Virtual Machine exits when the only threads running are all daemon threads. It could be that the threads you created are user threads and hence the JVM does not exit.

http://docs.oracle.com/javase/7/docs/api/java/lang/Thread.html#setDaemon(boolean)

I do have software that does not explicitly do this yet I do not have this problem so it could be the case that your threads do not know that they should stop running. You can fix this by having some sort of control flag that lets your threads know that they can stop now. Using an AtomicBoolean works well for this. If you are using Tomcat you can create a servlet to act as your main root to launch and control your thread. Tomcat promises to run your servlet's destroy() method upon shut down, which can properly stop your thread from running. Here is a rudimentary example of this.

@WebServlet(urlPatterns = {"/checkStatus"}, loadOnStartup = 1)
public class ThreadController extends HttpServlet {

    private AtomicBoolean running = new AtomicBoolean(false);
    private Thread myThread = new Thread() {

        @Override
        public void run() {
            while (running.get()) {
                //do stuff
            }
        }

    };

@Override
public void destroy() {
    running.set(false);
    myThread.interrupt();
}

@Override
public void init() throws ServletException {
    running.set(true);
    myThread.start();
}

}

Though in my implementation I use Executors to launch and interrupt my threads, but you can look that up further on your own.

Another option is to use a ScheduledExecutorService.

 private final ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
private ScheduledFuture<?> cleanUpHandle;


@Override
public void init() {
    cleanUpHandle = scheduler.scheduleAtFixedRate(cleanUp, 60, 60, TimeUnit.SECONDS);
}

@Override
public void destroy() {
    cleanUpHandle.cancel(true);
}

In my example above cleanUp is a Thread implementation. The good thing about using the scheduler is that you do not need a control while loop in your thread's run method. The run method just does one iteration of its task and finishes.

These are just a few things you can try and the right solution will be based on what you are trying to accomplish.

Answer 2

With Web service context listener WSServletContextListener and configure it in your web.xml and write the logic to stop all your threads in contextDestroyed Method. Clicking the Stop in Tomcat Manager will send an ServletContextEvent event to the

public void contextDestroyed(ServletContextEvent event)

Here, you can hijack the event and kill all your threads and release all your resources.That's the best place to stop your threads. Your web.xml should add the listener as follows. Ex :

      <listener>
//Fully qualified listener class name implementing javax.servlet.ServletContextListener
       <listener-class>XXX.XXX.XXX.YourListenerClass</listener-class>
     </listener>

Hope this gives an idea!