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74 lines
3.2 KiB
Java
74 lines
3.2 KiB
Java
/*
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* Copyright (c) 2005, 2017, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package com.sun.imageio.stream;
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import java.io.IOException;
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import javax.imageio.stream.ImageInputStream;
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/**
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* Small class to assist in properly closing an ImageInputStream instance
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* prior to garbage collection. The ImageInputStreamImpl class defines a
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* finalize() method, but in a number of its public subclasses
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* (e.g. FileImageInputStream) we override the finalize() method to be
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* empty for performance reasons, and instead rely on the Disposer mechanism
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* for closing/disposing resources. This is fine when one of these classes
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* is instantiated directly (e.g. new FileImageInputStream()) but in the
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* unlikely case where a user defines their own subclass of one of those
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* streams, we need some way to get back to the behavior of
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* ImageInputStreamImpl, which will call close() as part of finalization.
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*
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* Typically an Image{Input,Output}Stream will construct an instance of
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* StreamFinalizer in its constructor if it detects that it has been
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* subclassed by the user. The ImageInputStream instance will hold a
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* reference to the StreamFinalizer, and the StreamFinalizer will hold a
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* reference back to the ImageInputStream from which it was created. When
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* both are no longer reachable, the StreamFinalizer.finalize() method will
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* be called, which will take care of closing down the ImageInputStream.
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*
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* Clearly this is a bit of a hack, but it will likely only be used in the
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* rarest of circumstances: when a user has subclassed one of the public
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* stream classes. (It should be no worse than the old days when the public
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* stream classes had non-empty finalize() methods.)
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*/
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public class StreamFinalizer {
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private ImageInputStream stream;
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public StreamFinalizer(ImageInputStream stream) {
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this.stream = stream;
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}
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@SuppressWarnings("deprecation")
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protected void finalize() throws Throwable {
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try {
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stream.close();
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} catch (IOException e) {
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} finally {
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stream = null;
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super.finalize();
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}
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}
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}
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