Question

I have to create a progress bar in a webapp. I need a thread that do the work and a controller that tests this thread to get his status.
How to set it using beans (inside that thread I need to autowire some services)? Can I use thread as non-singleton bean?
Thank you.

Answer 1

I’d create a small wrapping class for this. You could have all of your setters in the class to handle the injected services, you could use InitializingBean to start the thread, and you can inject the bean into other classes so they could call getters on volatile or synchronized fields. Something like:

public class ProgressBar implements InitializingBean, Runnable, DisposableBean {
    private volatile int someField;
    private Thread thread;
    // start the thread after the properties are set
    public void afterPropertiesSet() {
        thread = new Thread(this);
        // maybe make it a daemon thread
        // thread.setDaemon(true);
        thread.start();
    }
    // stop it when spring is shutting down
    public void destroy() {
        thread.interrupt();
    }
    public void run() {
       ... thread code goes here
    }
    // spring setter
    public void setSomeService(SomeService someService) {
       this.someService = someService;
    }
    // getter used by other beans to get some value from this class
    public int getSomeField() {
        return someField;
    }
}

You could also use some of spring’s timer classes for this of course although they work better for repetitive tasks that run every so often.