001: /*
002:
003: ============================================================================
004: The Apache Software License, Version 1.1
005: ============================================================================
006:
007: Copyright (C) 1999-2003 The Apache Software Foundation. All rights reserved.
008:
009: Redistribution and use in source and binary forms, with or without modifica-
010: tion, are permitted provided that the following conditions are met:
011:
012: 1. Redistributions of source code must retain the above copyright notice,
013: this list of conditions and the following disclaimer.
014:
015: 2. Redistributions in binary form must reproduce the above copyright notice,
016: this list of conditions and the following disclaimer in the documentation
017: and/or other materials provided with the distribution.
018:
019: 3. The end-user documentation included with the redistribution, if any, must
020: include the following acknowledgment: "This product includes software
021: developed by the Apache Software Foundation (http://www.apache.org/)."
022: Alternately, this acknowledgment may appear in the software itself, if
023: and wherever such third-party acknowledgments normally appear.
024:
025: 4. The names "Batik" and "Apache Software Foundation" must not be
026: used to endorse or promote products derived from this software without
027: prior written permission. For written permission, please contact
028: apache@apache.org.
029:
030: 5. Products derived from this software may not be called "Apache", nor may
031: "Apache" appear in their name, without prior written permission of the
032: Apache Software Foundation.
033:
034: THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
035: INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
036: FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
037: APACHE SOFTWARE FOUNDATION OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
038: INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLU-
039: DING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
040: OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
041: ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
042: (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
043: THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
044:
045: This software consists of voluntary contributions made by many individuals
046: on behalf of the Apache Software Foundation. For more information on the
047: Apache Software Foundation, please see <http://www.apache.org/>.
048:
049: */
050:
051: package org.apache.batik.util;
052:
053: import java.lang.ref.Reference;
054: import java.lang.ref.ReferenceQueue;
055: import java.lang.ref.SoftReference;
056: import java.lang.ref.WeakReference;
057: import java.lang.ref.PhantomReference;
058:
059: /**
060: * One line Class Desc
061: *
062: * Complete Class Desc
063: *
064: * @author <a href="mailto:deweese@apache.org>l449433</a>
065: * @version $Id$
066: */
067: public class CleanerThread extends Thread {
068:
069: static ReferenceQueue queue = null;
070: static CleanerThread thread = null;
071:
072: public static ReferenceQueue getReferenceQueue() {
073: if (queue != null)
074: return queue;
075:
076: queue = new ReferenceQueue();
077: thread = new CleanerThread();
078: return queue;
079: }
080:
081: /**
082: * If objects registered with the reference queue associated with
083: * this class implement this interface then the 'cleared' method
084: * will be called when the reference is queued.
085: */
086: public static interface ReferenceCleared {
087: /* Called when the reference is cleared */
088: public void cleared();
089: }
090:
091: /**
092: * A SoftReference subclass that automatically registers with
093: * the cleaner ReferenceQueue.
094: */
095: public static abstract class SoftReferenceCleared extends
096: SoftReference implements ReferenceCleared {
097: public SoftReferenceCleared(Object o) {
098: super (o, CleanerThread.getReferenceQueue());
099: }
100: }
101:
102: /**
103: * A WeakReference subclass that automatically registers with
104: * the cleaner ReferenceQueue.
105: */
106: public static abstract class WeakReferenceCleared extends
107: WeakReference implements ReferenceCleared {
108: public WeakReferenceCleared(Object o) {
109: super (o, CleanerThread.getReferenceQueue());
110: }
111: }
112:
113: /**
114: * A PhantomReference subclass that automatically registers with
115: * the cleaner ReferenceQueue.
116: */
117: public static abstract class PhantomReferenceCleared extends
118: PhantomReference implements ReferenceCleared {
119: public PhantomReferenceCleared(Object o) {
120: super (o, CleanerThread.getReferenceQueue());
121: }
122: }
123:
124: protected CleanerThread() {
125: setDaemon(true);
126: start();
127: }
128:
129: public void run() {
130: while (true) {
131: try {
132: Reference ref;
133: try {
134: ref = queue.remove();
135: // System.err.println("Cleaned: " + ref);
136: } catch (InterruptedException ie) {
137: continue;
138: }
139:
140: if (ref instanceof ReferenceCleared) {
141: ReferenceCleared rc = (ReferenceCleared) ref;
142: rc.cleared();
143: }
144: } catch (ThreadDeath td) {
145: throw td;
146: } catch (Throwable t) {
147: t.printStackTrace();
148: }
149: }
150: }
151: }
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