1 /* 2 * Copyright (c) 2005, Oracle and/or its affiliates. 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. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * 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<CloseAction, Object> toCloseQueue; 47 private static Thread streamCloser; 48 49 public static void addToQueue(CloseAction ca) { 50 synchronized (StreamCloser.class) { 51 if (toCloseQueue == null) { 52 toCloseQueue = 53 new WeakHashMap<CloseAction, Object>(); 54 } 55 56 toCloseQueue.put(ca, 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<CloseAction> 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 CloseAction[] actions = 69 new CloseAction[set.size()]; 70 actions = set.toArray(actions); 71 for (CloseAction ca : actions) { 72 if (ca != null) { 73 try { 74 ca.performAction(); 75 } catch (IOException e) { 76 } 77 } 78 } 79 } 80 } 81 } 82 }; 83 84 java.security.AccessController.doPrivileged( 85 new java.security.PrivilegedAction<Object>() { 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 /* Set context class loader to null in order to avoid 98 * keeping a strong reference to an application classloader. 99 */ 100 streamCloser.setContextClassLoader(null); 101 Runtime.getRuntime().addShutdownHook(streamCloser); 102 return null; 103 } 104 }); 105 } 106 } 107 } 108 109 public static void removeFromQueue(CloseAction ca) { 110 synchronized (StreamCloser.class) { 111 if (toCloseQueue != null) { 112 toCloseQueue.remove(ca); 113 } 114 } 115 } 116 117 public static CloseAction createCloseAction(ImageInputStream iis) { 118 return new CloseAction(iis); 119 } 120 121 public static final class CloseAction { 122 private ImageInputStream iis; 123 124 private CloseAction(ImageInputStream iis) { 125 this.iis = iis; 126 } 127 128 public void performAction() throws IOException { 129 if (iis != null) { 130 iis.close(); 131 } 132 } 133 } 134 }