/*
* Copyright (c) 2005, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package com.sun.imageio.stream;
import java.io.IOException;
import java.util.Set;
import java.util.WeakHashMap;
import javax.imageio.stream.ImageInputStream;
/**
* This class provide means to properly close hanging
* image input/output streams on VM shutdown.
* This might be useful for proper cleanup such as removal
* of temporary files.
*
* Addition of stream do not prevent it from being garbage collected
* if no other references to it exists. Stream can be closed
* explicitly without removal from StreamCloser queue.
* Explicit removal from the queue only helps to save some memory.
*/
public class StreamCloser {
private static WeakHashMap<CloseAction, Object> toCloseQueue;
private static Thread streamCloser;
public static void addToQueue(CloseAction ca) {
synchronized (StreamCloser.class) {
if (toCloseQueue == null) {
toCloseQueue =
new WeakHashMap<CloseAction, Object>();
}
toCloseQueue.put(ca, null);
if (streamCloser == null) {
final Runnable streamCloserRunnable = new Runnable() {
public void run() {
if (toCloseQueue != null) {
synchronized (StreamCloser.class) {
Set<CloseAction> set =
toCloseQueue.keySet();
// Make a copy of the set in order to avoid
// concurrent modification (the is.close()
// will in turn call removeFromQueue())
CloseAction[] actions =
new CloseAction[set.size()];
actions = set.toArray(actions);
for (CloseAction ca : actions) {
if (ca != null) {
try {
ca.performAction();
} catch (IOException e) {
}
}
}
}
}
}
};
java.security.AccessController.doPrivileged(
new java.security.PrivilegedAction() {
public Object run() {
/* The thread must be a member of a thread group
* which will not get GCed before VM exit.
* Make its parent the top-level thread group.
*/
ThreadGroup tg =
Thread.currentThread().getThreadGroup();
for (ThreadGroup tgn = tg;
tgn != null;
tg = tgn, tgn = tg.getParent());
streamCloser = new Thread(tg, streamCloserRunnable);
Runtime.getRuntime().addShutdownHook(streamCloser);
return null;
}
});
}
}
}
public static void removeFromQueue(CloseAction ca) {
synchronized (StreamCloser.class) {
if (toCloseQueue != null) {
toCloseQueue.remove(ca);
}
}
}
public static CloseAction createCloseAction(ImageInputStream iis) {
return new CloseAction(iis);
}
public static final class CloseAction {
private ImageInputStream iis;
private CloseAction(ImageInputStream iis) {
this.iis = iis;
}
public void performAction() throws IOException {
if (iis != null) {
iis.close();
}
}
}
}