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