1/* 2 * Copyright (c) 2005, 2017, 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 26package com.sun.imageio.stream; 27 28import java.io.IOException; 29import javax.imageio.stream.ImageInputStream; 30 31/** 32 * Small class to assist in properly closing an ImageInputStream instance 33 * prior to garbage collection. The ImageInputStreamImpl class defines a 34 * finalize() method, but in a number of its public subclasses 35 * (e.g. FileImageInputStream) we override the finalize() method to be 36 * empty for performance reasons, and instead rely on the Disposer mechanism 37 * for closing/disposing resources. This is fine when one of these classes 38 * is instantiated directly (e.g. new FileImageInputStream()) but in the 39 * unlikely case where a user defines their own subclass of one of those 40 * streams, we need some way to get back to the behavior of 41 * ImageInputStreamImpl, which will call close() as part of finalization. 42 * 43 * Typically an Image{Input,Output}Stream will construct an instance of 44 * StreamFinalizer in its constructor if it detects that it has been 45 * subclassed by the user. The ImageInputStream instance will hold a 46 * reference to the StreamFinalizer, and the StreamFinalizer will hold a 47 * reference back to the ImageInputStream from which it was created. When 48 * both are no longer reachable, the StreamFinalizer.finalize() method will 49 * be called, which will take care of closing down the ImageInputStream. 50 * 51 * Clearly this is a bit of a hack, but it will likely only be used in the 52 * rarest of circumstances: when a user has subclassed one of the public 53 * stream classes. (It should be no worse than the old days when the public 54 * stream classes had non-empty finalize() methods.) 55 */ 56public class StreamFinalizer { 57 private ImageInputStream stream; 58 59 public StreamFinalizer(ImageInputStream stream) { 60 this.stream = stream; 61 } 62 63 @SuppressWarnings("deprecation") 64 protected void finalize() throws Throwable { 65 try { 66 stream.close(); 67 } catch (IOException e) { 68 } finally { 69 stream = null; 70 super.finalize(); 71 } 72 } 73} 74