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