Class SwingWorker
- All Implemented Interfaces:
Runnable
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
- Author:
- Joseph Bowbeer, Hans Muller
-
Nested Class Summary
Nested classes/interfaces inherited from class EDU.oswego.cs.dl.util.concurrent.ThreadFactoryUser
ThreadFactoryUser.DefaultThreadFactory
-
Field Summary
Fields inherited from class EDU.oswego.cs.dl.util.concurrent.ThreadFactoryUser
threadFactory_
-
Constructor Summary
ConstructorsModifierConstructorDescriptionCreates 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
Modifier and TypeMethodDescriptionprotected abstract Object
Computes the value to be returned by theget
method.protected void
finished()
Called on the event dispatching thread (not on the worker thread) after theconstruct
method has returned.get()
Return the value created by theconstruct
method, waiting if necessary until it is ready.Get the exception, or null if there isn't one (yet).long
Returns timeout period in milliseconds.void
Stops the worker and sets the exception to InterruptedException.boolean
isReady()
Return whether theget
method is ready to return a value.void
run()
Calls theconstruct
method to compute the result, and then invokes thefinished
method on the event dispatch thread.void
start()
Starts the worker thread.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
-
Constructor Details
-
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, or0
for no time limit.
-
SwingWorker
Creates new SwingWorker with specified thread factory and timeout.- Parameters:
factory
- factory for worker threads.msecs
- timeout in milliseconds, or0
for no time limit.
-
-
Method Details
-
construct
Computes the value to be returned by theget
method.- Throws:
Exception
-
finished
protected void finished()Called on the event dispatching thread (not on the worker thread) after theconstruct
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 is0
(default). -
run
public void run()Calls theconstruct
method to compute the result, and then invokes thefinished
method on the event dispatch thread. -
start
public void start()Starts the worker thread. -
interrupt
public void interrupt()Stops the worker and sets the exception to InterruptedException. -
get
Return the value created by theconstruct
method, waiting if necessary until it is ready.- Returns:
- the value created by the
construct
method - Throws:
InterruptedException
- if current thread was interruptedInvocationTargetException
- if the constructing thread encountered an exception or was interrupted.
-
timedGet
public Object timedGet(long msecs) throws TimeoutException, InterruptedException, InvocationTargetException Wait at most msecs to access the constructed result.- Returns:
- current value
- Throws:
TimeoutException
- if not ready after msecsInterruptedException
- if current thread has been interruptedInvocationTargetException
- if the constructing thread encountered an exception or was interrupted.
-
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 theget
method is ready to return a value.- Returns:
- true if a value or exception has been set. else false
-