Showing the changes to java/pkg/com/sun/imageio/stream/StreamFinalizer.java (1 of 18352 files). Show all
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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 | +} | |