001: /*
002: * Copyright (c) 2001 Silvere Martin-Michiellot All Rights Reserved.
003: *
004: * Silvere Martin-Michiellot grants you ("Licensee") a non-exclusive,
005: * royalty free, license to use, modify and redistribute this
006: * software in source and binary code form,
007: * provided that i) this copyright notice and license appear on all copies of
008: * the software; and ii) Licensee does not utilize the software in a manner
009: * which is disparaging to Silvere Martin-Michiellot.
010: *
011: * This software is provided "AS IS," without a warranty of any kind. ALL
012: * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING ANY
013: * IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR
014: * NON-INFRINGEMENT, ARE HEREBY EXCLUDED. Silvere Martin-Michiellot
015: * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES
016: * SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING
017: * OR DISTRIBUTING THE SOFTWARE OR ITS DERIVATIVES. IN NO EVENT WILL
018: * Silvere Martin-Michiellot OR ITS LICENSORS BE LIABLE
019: * FOR ANY LOST REVENUE, PROFIT OR DATA, OR FOR DIRECT,
020: * INDIRECT, SPECIAL, CONSEQUENTIAL, INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER
021: * CAUSED AND REGARDLESS OF THE THEORY OF LIABILITY, ARISING OUT OF THE USE OF
022: * OR INABILITY TO USE SOFTWARE, EVEN IF Silvere Martin-Michiellot HAS BEEN
023: * ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
024: *
025: * This software is not designed or intended for use in on-line control of
026: * aircraft, air traffic, aircraft navigation or aircraft communications; or in
027: * the design, construction, operation or maintenance of any nuclear
028: * facility. Licensee represents and warrants that it will not use or
029: * redistribute the Software for such purposes.
030: *
031: * @Author: Silvere Martin-Michiellot
032: *
033: */
034:
035: package com.db.utils.task;
036:
037: import javax.swing.SwingUtilities;
038:
039: /**
040: * This is the 3rd version of SwingWorker (also known as
041: * SwingWorker 3), an abstract class that you subclass to
042: * perform GUI-related work in a dedicated thread. For
043: * instructions on using this class, see:
044: *
045: * http://java.sun.com/docs/books/tutorial/uiswing/misc/threads.html
046: *
047: * Note that the API changed slightly in the 3rd version:
048: * You must now invoke start() on the SwingWorker after
049: * creating it.
050: */
051: public abstract class SwingWorker {
052:
053: private Object value; // see getValue(), setValue()
054: private Thread thread;
055:
056: /**
057: * Class to maintain reference to current worker thread
058: * under separate synchronization control.
059: */
060: private static class ThreadVar {
061:
062: private Thread thread;
063:
064: ThreadVar(Thread t) {
065:
066: thread = t;
067:
068: }
069:
070: synchronized Thread get() {
071:
072: return thread;
073:
074: }
075:
076: synchronized void clear() {
077:
078: thread = null;
079:
080: }
081:
082: }
083:
084: private ThreadVar threadVar;
085:
086: /**
087: * Get the value produced by the worker thread, or null if it
088: * hasn't been constructed yet.
089: */
090: protected synchronized Object getValue() {
091:
092: return value;
093:
094: }
095:
096: /**
097: * Set the value produced by worker thread
098: */
099: private synchronized void setValue(Object x) {
100:
101: value = x;
102:
103: }
104:
105: /**
106: * Compute the value to be returned by the <code>get</code> method.
107: */
108: public abstract Object construct();
109:
110: /**
111: * Called on the event dispatching thread (not on the worker thread)
112: * after the <code>construct</code> method has returned.
113: */
114: public void finished() {
115: }
116:
117: /**
118: * A new method that interrupts the worker thread. Call this method
119: * to force the worker to stop what it's doing.
120: */
121: public void interrupt() {
122:
123: Thread t = threadVar.get();
124: if (t != null) {
125: t.interrupt();
126: }
127: threadVar.clear();
128:
129: }
130:
131: /**
132: * Return the value created by the <code>construct</code> method.
133: * Returns null if either the constructing thread or the current
134: * thread was interrupted before a value was produced.
135: *
136: * @return the value created by the <code>construct</code> method
137: */
138: public Object get() {
139:
140: while (true) {
141: Thread t = threadVar.get();
142: if (t == null) {
143: return getValue();
144: }
145: try {
146: t.join();
147: } catch (InterruptedException e) {
148: Thread.currentThread().interrupt(); // propagate
149: return null;
150: }
151: }
152:
153: }
154:
155: /**
156: * Start a thread that will call the <code>construct</code> method
157: * and then exit.
158: */
159: public SwingWorker() {
160:
161: final Runnable doFinished = new Runnable() {
162: public void run() {
163: finished();
164: }
165: };
166:
167: Runnable doConstruct = new Runnable() {
168:
169: public void run() {
170:
171: try {
172: setValue(construct());
173: } finally {
174: threadVar.clear();
175: }
176:
177: SwingUtilities.invokeLater(doFinished);
178:
179: }
180: };
181:
182: Thread t = new Thread(doConstruct);
183: threadVar = new ThreadVar(t);
184:
185: }
186:
187: /**
188: * Start the worker thread.
189: */
190: public void start() {
191:
192: Thread t = threadVar.get();
193: if (t != null) {
194: t.start();
195: }
196:
197: }
198:
199: }
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