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| 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 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 | */ | ||
| 56 | public class StreamFinalizer { | ||
| 57 | private ImageInputStream stream; | ||
| 58 | |||
| 59 | public StreamFinalizer(ImageInputStream stream) { | ||
| 60 | this.stream = stream; | ||
| 61 | } | ||
| 62 | |||
| 63 | protected void finalize() throws Throwable { | ||
| 64 | try { | ||
| 65 | stream.close(); | ||
| 66 | } catch (IOException e) { | ||
| 67 | } finally { | ||
| 68 | stream = null; | ||
| 69 | super.finalize(); | ||
| 70 | } | ||
| 71 | } | ||
| 72 | } | ||