Class SwingWorker

  • All Implemented Interfaces:
    java.lang.Runnable

    public abstract class SwingWorker
    extends ThreadFactoryUser
    implements java.lang.Runnable
    An abstract class that you subclass to perform GUI-related work in a dedicated thread.

    This class was adapted from the SwingWorker written by Hans Muller and presented in "Using a Swing Worker Thread" in the Swing Connection - http://java.sun.com/products/jfc/tsc/articles/threads/threads2.html

    A closely related version of this class is described in "The Last Word in Swing Threads" in the Swing Connection - http://java.sun.com/products/jfc/tsc/articles/threads/threads3.html

    This SwingWorker is a ThreadFactoryUser and implements Runnable. The default thread factory creates low-priority worker threads. A special constructor is provided for enabling a timeout. When the timeout expires, the worker thread is interrupted.

    Note: Using a timeout of Long.MAX_VALUE will not impose a timeout but will create an additional thread of control that will respond to an interrupt even if the construct implementation ignores them.

    Sample Usage

     import EDU.oswego.cs.dl.util.concurrent.TimeoutException;
     import EDU.oswego.cs.dl.util.concurrent.misc.SwingWorker;
    
     public class SwingWorkerDemo extends javax.swing.JApplet {
    
       private static final int TIMEOUT = 5000; // 5 seconds
       private javax.swing.JLabel status;
       private javax.swing.JButton start;
       private SwingWorker worker;
    
       public SwingWorkerDemo() {
         status = new javax.swing.JLabel("Ready");
         status.setHorizontalAlignment(javax.swing.SwingConstants.CENTER);
         getContentPane().add(status, java.awt.BorderLayout.CENTER);
         start = new javax.swing.JButton("Start");
         getContentPane().add(start, java.awt.BorderLayout.SOUTH);
    
         start.addActionListener(new java.awt.event.ActionListener() {
           public void actionPerformed(java.awt.event.ActionEvent evt) {
             if (start.getText().equals("Start")) {
               start.setText("Stop");
               status.setText("Working...");
               worker = new DemoSwingWorker(TIMEOUT);
               worker.start();
             } else {
               worker.interrupt();
             }
           }
         });
       }
    
       private class DemoSwingWorker extends SwingWorker {
         private static final java.util.Random RAND = new java.util.Random();
         public DemoSwingWorker(long msecs) {
           super(msecs);
         }
         protected Object construct() throws InterruptedException {
           // Take a random nap. If we oversleep, the worker times out.
           Thread.sleep(RAND.nextInt(2*TIMEOUT));
           return "Success";
         }
         protected void finished() {
           start.setText("Start");
           try {
             Object result = get();
             status.setText((String) result);
           }
           catch (java.lang.reflect.InvocationTargetException e) {
             Throwable ex = e.getTargetException();
             if (ex instanceof TimeoutException) {
               status.setText("Timed out.");
             } else if (ex instanceof InterruptedException) {
               status.setText("Interrupted.");
             } else {
               status.setText("Exception: " + ex);
             }
           }
           catch (InterruptedException ex) {
             // event-dispatch thread won't be interrupted 
             throw new IllegalStateException(ex+"");
           }
         }
       }
     }
     
    Version:
    3.0

    [ Introduction to this package. ]

    Author:
    Joseph Bowbeer, Hans Muller
    • Constructor Summary

      Constructors 
      Modifier Constructor Description
        SwingWorker()
      Creates new SwingWorker with no timeout.
        SwingWorker​(long msecs)
      Creates new SwingWorker with specified timeout.
      protected SwingWorker​(ThreadFactory factory, long msecs)
      Creates new SwingWorker with specified thread factory and timeout.
    • Method Summary

      All Methods Instance Methods Abstract Methods Concrete Methods 
      Modifier and Type Method Description
      protected abstract java.lang.Object construct()
      Computes the value to be returned by the get method.
      protected void finished()
      Called on the event dispatching thread (not on the worker thread) after the construct method has returned.
      java.lang.Object get()
      Return the value created by the construct method, waiting if necessary until it is ready.
      java.lang.reflect.InvocationTargetException getException()
      Get the exception, or null if there isn't one (yet).
      long getTimeout()
      Returns timeout period in milliseconds.
      void interrupt()
      Stops the worker and sets the exception to InterruptedException.
      boolean isReady()
      Return whether the get method is ready to return a value.
      void run()
      Calls the construct method to compute the result, and then invokes the finished method on the event dispatch thread.
      void start()
      Starts the worker thread.
      java.lang.Object timedGet​(long msecs)
      Wait at most msecs to access the constructed result.
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    • Constructor Detail

      • SwingWorker

        public SwingWorker()
        Creates new SwingWorker with no timeout.
      • SwingWorker

        public SwingWorker​(long msecs)
        Creates new SwingWorker with specified timeout.
        Parameters:
        msecs - timeout in milliseconds, or 0 for no time limit.
      • SwingWorker

        protected SwingWorker​(ThreadFactory factory,
                              long msecs)
        Creates new SwingWorker with specified thread factory and timeout.
        Parameters:
        factory - factory for worker threads.
        msecs - timeout in milliseconds, or 0 for no time limit.
    • Method Detail

      • construct

        protected abstract java.lang.Object construct()
                                               throws java.lang.Exception
        Computes the value to be returned by the get method.
        Throws:
        java.lang.Exception
      • finished

        protected void finished()
        Called on the event dispatching thread (not on the worker thread) after the construct method has returned.
      • getTimeout

        public long getTimeout()
        Returns timeout period in milliseconds. Timeout is the maximum time to wait for worker to complete. There is no time limit if timeout is 0 (default).
      • run

        public void run()
        Calls the construct method to compute the result, and then invokes the finished method on the event dispatch thread.
        Specified by:
        run in interface java.lang.Runnable
      • start

        public void start()
        Starts the worker thread.
      • interrupt

        public void interrupt()
        Stops the worker and sets the exception to InterruptedException.
      • get

        public java.lang.Object get()
                             throws java.lang.InterruptedException,
                                    java.lang.reflect.InvocationTargetException
        Return the value created by the construct method, waiting if necessary until it is ready.
        Returns:
        the value created by the construct method
        Throws:
        java.lang.InterruptedException - if current thread was interrupted
        java.lang.reflect.InvocationTargetException - if the constructing thread encountered an exception or was interrupted.
      • timedGet

        public java.lang.Object timedGet​(long msecs)
                                  throws TimeoutException,
                                         java.lang.InterruptedException,
                                         java.lang.reflect.InvocationTargetException
        Wait at most msecs to access the constructed result.
        Returns:
        current value
        Throws:
        TimeoutException - if not ready after msecs
        java.lang.InterruptedException - if current thread has been interrupted
        java.lang.reflect.InvocationTargetException - if the constructing thread encountered an exception or was interrupted.
      • getException

        public java.lang.reflect.InvocationTargetException getException()
        Get the exception, or null if there isn't one (yet). This does not wait until the worker is ready, so should ordinarily only be called if you know it is.
        Returns:
        the exception encountered by the construct method wrapped in an InvocationTargetException
      • isReady

        public boolean isReady()
        Return whether the get method is ready to return a value.
        Returns:
        true if a value or exception has been set. else false