Question

I am writing a servlet, which must start a thread in init() and correctly stop it after the server is stopped. Thread downloads a web page, parses it and stores data in MySQL database.

For stopping the thread I use servlet’s destroy() method. In this method I set condition for ending my thread. Is this the right way of doing it?

Can I see signs of the existence of my thread somewhere in my Windows? I didn’t find it in Windows Task Manager.

Answer 1

The Windows task manager only shows processes, not individual threads. In fact, JVM-managed threads fall in the category of User threads, which is a distinct category from Kernel threads (managed by the operating system).

To do what you want you will have to keep a global reference to your Thread object, such that it’s visible across different methods. It’s also preferable to make your thread spin on a flag and stop it by setting the flag, instead of using something like Thread.stop(). Something like this:

class ThreadTask implements Runnable {
    private volatile boolean flag = false;

    public void setFlag(boolean value) {
        flag = value;
    }

    public void run() {
        while(!flag) {
           // execute code
        }
    }
}

And stop it by calling setFlag(true).