001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 * 
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 * 
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.io.input;
018
019import java.io.IOException;
020import java.io.InputStream;
021
022/**
023 * Proxy stream that closes and discards the underlying stream as soon as the
024 * end of input has been reached or when the stream is explicitly closed.
025 * Not even a reference to the underlying stream is kept after it has been
026 * closed, so any allocated in-memory buffers can be freed even if the
027 * client application still keeps a reference to the proxy stream.
028 * <p>
029 * This class is typically used to release any resources related to an open
030 * stream as soon as possible even if the client application (by not explicitly
031 * closing the stream when no longer needed) or the underlying stream (by not
032 * releasing resources once the last byte has been read) do not do that.
033 *
034 * @version $Id: AutoCloseInputStream.java 1304052 2012-03-22 20:55:29Z ggregory $
035 * @since 1.4
036 */
037public class AutoCloseInputStream extends ProxyInputStream {
038
039    /**
040     * Creates an automatically closing proxy for the given input stream.
041     *
042     * @param in underlying input stream
043     */
044    public AutoCloseInputStream(InputStream in) {
045        super(in);
046    }
047
048    /**
049     * Closes the underlying input stream and replaces the reference to it
050     * with a {@link ClosedInputStream} instance.
051     * <p>
052     * This method is automatically called by the read methods when the end
053     * of input has been reached.
054     * <p>
055     * Note that it is safe to call this method any number of times. The original
056     * underlying input stream is closed and discarded only once when this
057     * method is first called.
058     *
059     * @throws IOException if the underlying input stream can not be closed
060     */
061    @Override
062    public void close() throws IOException {
063        in.close();
064        in = new ClosedInputStream();
065    }
066
067    /**
068     * Automatically closes the stream if the end of stream was reached.
069     *
070     * @param n number of bytes read, or -1 if no more bytes are available
071     * @throws IOException if the stream could not be closed
072     * @since 2.0
073     */
074    @Override
075    protected void afterRead(int n) throws IOException {
076        if (n == -1) {
077            close();
078        }
079    }
080
081    /**
082     * Ensures that the stream is closed before it gets garbage-collected.
083     * As mentioned in {@link #close()}, this is a no-op if the stream has
084     * already been closed.
085     * @throws Throwable if an error occurs
086     */
087    @Override
088    protected void finalize() throws Throwable {
089        close();
090        super.finalize();
091    }
092
093}