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/*
* @(#)Worker.java
*
* Copyright (c) 1996-2010 by the original authors of JHotDraw and all its
* contributors. All rights reserved.
*
* You may not use, copy or modify this file, except in compliance with the
* license agreement you entered into with the copyright holders. For details
* see accompanying license terms.
*/
package org.jhotdraw.gui;
import edu.umd.cs.findbugs.annotations.Nullable;
import javax.swing.SwingUtilities;
/**
* This is an abstract class that you can subclass to
* perform GUI-related work in a dedicated event dispatcher.
*
* This class is similar to SwingWorker but less complex.
*
* @author Werner Randelshofer
* @version $Id: Worker.java 717 2010-11-21 12:30:57Z rawcoder $
*/
public abstract class Worker implements Runnable {
private T value; // see getValue(), setValue()
private Throwable error; // see getError(), setError()
/**
* Calls #construct on the current thread and invokes
* #done on the AWT event dispatcher thread.
*/
@Override
public final void run() {
try {
setValue(construct());
} catch (Throwable e) {
setError(e);
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
failed(getError());
finished();
}
});
return;
}
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
done(getValue());
finished();
}
});
}
/**
* Compute the value to be returned by the get method.
*/
@Nullable protected abstract T construct() throws Exception;
/**
* Called on the event dispatching thread (not on the worker thread)
* after the construct method has returned without throwing
* an error.
*
* The default implementation does nothing. Subclasses may override this
* method to perform done actions on the Event Dispatch Thread.
*
* @param value The return value of the construct method.
*/
protected void done(@Nullable T value) {
}
/**
* Called on the event dispatching thread (not on the worker thread)
* after the construct method has thrown an error.
*
* The default implementation prints a stack trace. Subclasses may override
* this method to perform failure actions on the Event Dispatch Thread.
*
* @param error The error thrown by construct.
*/
protected void failed(Throwable error) {
error.printStackTrace();
}
/**
* Called on the event dispatching thread (not on the worker thread)
* after the construct method has finished and after
* done() or failed() has been invoked.
*
* The default implementation does nothing. Subclasses may override this
* method to perform completion actions on the Event Dispatch Thread.
*/
protected void finished() {
}
/**
* Get the value produced by the worker thread, or null if it
* hasn't been constructed yet.
*/
protected synchronized T getValue() {
return value;
}
/**
* Set the value produced by construct.
*/
private synchronized void setValue(T x) {
value = x;
}
/**
* Get the error produced by the worker thread, or null if it
* hasn't thrown one.
*/
protected synchronized Throwable getError() {
return error;
}
/**
* Set the error thrown by constrct.
*/
private synchronized void setError(Throwable x) {
error = x;
}
/**
* Starts the Worker on an internal worker thread.
*/
public void start() {
new Thread(this).start();
}
}