1 /* 2 * Copyright (c) 2005, 2015, 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 sun.awt.util.ThreadGroupUtils; 29 30 import java.io.IOException; 31 import java.security.AccessController; 32 import java.security.PrivilegedAction; 33 import java.util.Set; 34 import java.util.WeakHashMap; 35 import javax.imageio.stream.ImageInputStream; 36 37 /** 38 * This class provide means to properly close hanging 39 * image input/output streams on VM shutdown. 40 * This might be useful for proper cleanup such as removal 41 * of temporary files. 42 * 43 * Addition of stream do not prevent it from being garbage collected 44 * if no other references to it exists. Stream can be closed 45 * explicitly without removal from StreamCloser queue. 46 * Explicit removal from the queue only helps to save some memory. 47 */ 48 public class StreamCloser { 49 50 private static WeakHashMap<CloseAction, Object> toCloseQueue; 51 private static Thread streamCloser; 52 53 public static void addToQueue(CloseAction ca) { 54 synchronized (StreamCloser.class) { 55 if (toCloseQueue == null) { 56 toCloseQueue = 57 new WeakHashMap<CloseAction, Object>(); 58 } 59 60 toCloseQueue.put(ca, null); 61 62 if (streamCloser == null) { 63 final Runnable streamCloserRunnable = new Runnable() { 64 public void run() { 65 if (toCloseQueue != null) { 66 synchronized (StreamCloser.class) { 67 Set<CloseAction> set = 68 toCloseQueue.keySet(); 69 // Make a copy of the set in order to avoid 70 // concurrent modification (the is.close() 71 // will in turn call removeFromQueue()) 72 CloseAction[] actions = 73 new CloseAction[set.size()]; 74 actions = set.toArray(actions); 75 for (CloseAction ca : actions) { 76 if (ca != null) { 77 try { 78 ca.performAction(); 79 } catch (IOException e) { 80 } 81 } 82 } 83 } 84 } 85 } 86 }; 87 88 AccessController.doPrivileged((PrivilegedAction<Object>) () -> { 89 /* The thread must be a member of a thread group 90 * which will not get GCed before VM exit. 91 * Make its parent the top-level thread group. 92 */ 93 ThreadGroup tg = ThreadGroupUtils.getRootThreadGroup(); 94 streamCloser = new Thread(tg, streamCloserRunnable, 95 "StreamCloser", 0, false); 96 /* Set context class loader to null in order to avoid 97 * keeping a strong reference to an application classloader. 98 */ 99 streamCloser.setContextClassLoader(null); 100 Runtime.getRuntime().addShutdownHook(streamCloser); 101 return null; 102 }); 103 } 104 } 105 } 106 107 public static void removeFromQueue(CloseAction ca) { 108 synchronized (StreamCloser.class) { 109 if (toCloseQueue != null) { 110 toCloseQueue.remove(ca); 111 } 112 } 113 } 114 115 public static CloseAction createCloseAction(ImageInputStream iis) { 116 return new CloseAction(iis); 117 } 118 119 public static final class CloseAction { 120 private ImageInputStream iis; 121 122 private CloseAction(ImageInputStream iis) { 123 this.iis = iis; 124 } 125 126 public void performAction() throws IOException { 127 if (iis != null) { 128 iis.close(); 129 } 130 } 131 } 132 }