EDU.oswego.cs.dl.util.concurrent.misc
Class SwingWorker

java.lang.Object
  |
  +--EDU.oswego.cs.dl.util.concurrent.ThreadFactoryUser
        |
        +--EDU.oswego.cs.dl.util.concurrent.misc.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+"");
       }
     }
   }
 }
 

Constructor Summary

SwingWorker()
Creates new SwingWorker with no timeout.

SwingWorker(long msecs)
Creates new SwingWorker with specified timeout.

Method Summary

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 EDU.oswego.cs.dl.util.concurrent.ThreadFactoryUser

getThreadFactory, setThreadFactory

Methods inherited from class java.lang.Object

equals, 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.

Method Detail

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