Class SwingWorker
- java.lang.Object
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- EDU.oswego.cs.dl.util.concurrent.ThreadFactoryUser
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- EDU.oswego.cs.dl.util.concurrent.misc.SwingWorker
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- 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 theconstruct
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
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Nested Class Summary
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Nested classes/interfaces inherited from class EDU.oswego.cs.dl.util.concurrent.ThreadFactoryUser
ThreadFactoryUser.DefaultThreadFactory
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Field Summary
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Fields inherited from class EDU.oswego.cs.dl.util.concurrent.ThreadFactoryUser
threadFactory_
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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.
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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 theget
method.protected void
finished()
Called on the event dispatching thread (not on the worker thread) after theconstruct
method has returned.java.lang.Object
get()
Return the value created by theconstruct
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 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.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
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Constructor Detail
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SwingWorker
public SwingWorker()
Creates new SwingWorker with no timeout.
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SwingWorker
public SwingWorker(long msecs)
Creates new SwingWorker with specified timeout.- Parameters:
msecs
- timeout in milliseconds, or0
for no time limit.
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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, or0
for no time limit.
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Method Detail
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construct
protected abstract java.lang.Object construct() throws java.lang.Exception
Computes the value to be returned by theget
method.- Throws:
java.lang.Exception
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finished
protected void finished()
Called on the event dispatching thread (not on the worker thread) after theconstruct
method has returned.
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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).
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run
public void run()
Calls theconstruct
method to compute the result, and then invokes thefinished
method on the event dispatch thread.- Specified by:
run
in interfacejava.lang.Runnable
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start
public void start()
Starts the worker thread.
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interrupt
public void interrupt()
Stops the worker and sets the exception to InterruptedException.
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get
public java.lang.Object get() throws java.lang.InterruptedException, java.lang.reflect.InvocationTargetException
Return the value created by theconstruct
method, waiting if necessary until it is ready.- Returns:
- the value created by the
construct
method - Throws:
java.lang.InterruptedException
- if current thread was interruptedjava.lang.reflect.InvocationTargetException
- if the constructing thread encountered an exception or was interrupted.
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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 msecsjava.lang.InterruptedException
- if current thread has been interruptedjava.lang.reflect.InvocationTargetException
- if the constructing thread encountered an exception or was interrupted.
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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
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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
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