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