J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 2005 Sun Microsystems, Inc. All Rights Reserved. |
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| 4 | * |
| 5 | * This code is free software; you can redistribute it and/or modify it |
| 6 | * under the terms of the GNU General Public License version 2 only, as |
| 7 | * published by the Free Software Foundation. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun in the LICENSE file that accompanied this code. |
| 10 | * |
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT |
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| 14 | * version 2 for more details (a copy is included in the LICENSE file that |
| 15 | * accompanied this code). |
| 16 | * |
| 17 | * You should have received a copy of the GNU General Public License version |
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, |
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| 20 | * |
| 21 | * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any questions. |
| 24 | */ |
| 25 | |
| 26 | package com.sun.imageio.stream; |
| 27 | |
| 28 | import java.io.IOException; |
| 29 | import java.util.Set; |
| 30 | import java.util.WeakHashMap; |
| 31 | import javax.imageio.stream.ImageInputStream; |
| 32 | |
| 33 | /** |
| 34 | * This class provide means to properly close hanging |
| 35 | * image input/output streams on VM shutdown. |
| 36 | * This might be useful for proper cleanup such as removal |
| 37 | * of temporary files. |
| 38 | * |
| 39 | * Addition of stream do not prevent it from being garbage collected |
| 40 | * if no other references to it exists. Stream can be closed |
| 41 | * explicitly without removal from StreamCloser queue. |
| 42 | * Explicit removal from the queue only helps to save some memory. |
| 43 | */ |
| 44 | public class StreamCloser { |
| 45 | |
| 46 | private static WeakHashMap<ImageInputStream, Object> toCloseQueue; |
| 47 | private static Thread streamCloser; |
| 48 | |
| 49 | public static void addToQueue(ImageInputStream iis) { |
| 50 | synchronized (StreamCloser.class) { |
| 51 | if (toCloseQueue == null) { |
| 52 | toCloseQueue = |
| 53 | new WeakHashMap<ImageInputStream, Object>(); |
| 54 | } |
| 55 | |
| 56 | toCloseQueue.put(iis, null); |
| 57 | |
| 58 | if (streamCloser == null) { |
| 59 | final Runnable streamCloserRunnable = new Runnable() { |
| 60 | public void run() { |
| 61 | if (toCloseQueue != null) { |
| 62 | synchronized (StreamCloser.class) { |
| 63 | Set<ImageInputStream> set = |
| 64 | toCloseQueue.keySet(); |
| 65 | // Make a copy of the set in order to avoid |
| 66 | // concurrent modification (the is.close() |
| 67 | // will in turn call removeFromQueue()) |
| 68 | ImageInputStream[] streams = |
| 69 | new ImageInputStream[set.size()]; |
| 70 | streams = set.toArray(streams); |
| 71 | for (ImageInputStream is : streams) { |
| 72 | if (is != null) { |
| 73 | try { |
| 74 | is.close(); |
| 75 | } catch (IOException e) { |
| 76 | } |
| 77 | } |
| 78 | } |
| 79 | } |
| 80 | } |
| 81 | } |
| 82 | }; |
| 83 | |
| 84 | java.security.AccessController.doPrivileged( |
| 85 | new java.security.PrivilegedAction() { |
| 86 | public Object run() { |
| 87 | /* The thread must be a member of a thread group |
| 88 | * which will not get GCed before VM exit. |
| 89 | * Make its parent the top-level thread group. |
| 90 | */ |
| 91 | ThreadGroup tg = |
| 92 | Thread.currentThread().getThreadGroup(); |
| 93 | for (ThreadGroup tgn = tg; |
| 94 | tgn != null; |
| 95 | tg = tgn, tgn = tg.getParent()); |
| 96 | streamCloser = new Thread(tg, streamCloserRunnable); |
| 97 | Runtime.getRuntime().addShutdownHook(streamCloser); |
| 98 | return null; |
| 99 | } |
| 100 | }); |
| 101 | } |
| 102 | } |
| 103 | } |
| 104 | |
| 105 | public static void removeFromQueue(ImageInputStream iis) { |
| 106 | synchronized (StreamCloser.class) { |
| 107 | if (toCloseQueue != null) { |
| 108 | toCloseQueue.remove(iis); |
| 109 | } |
| 110 | } |
| 111 | } |
| 112 | } |