    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 static org.apache.commons.io.IOUtils.EOF;
    020
    021import java.io.IOException;
    022import java.io.InputStream;
    023
    024/**
    025 * Proxy stream that closes and discards the underlying stream as soon as the
    026 * end of input has been reached or when the stream is explicitly closed.
    027 * Not even a reference to the underlying stream is kept after it has been
    028 * closed, so any allocated in-memory buffers can be freed even if the
    029 * client application still keeps a reference to the proxy stream.
    030 * <p>
    031 * This class is typically used to release any resources related to an open
    032 * stream as soon as possible even if the client application (by not explicitly
    033 * closing the stream when no longer needed) or the underlying stream (by not
    034 * releasing resources once the last byte has been read) do not do that.
    035 * </p>
    036 *
    037 * @since 1.4
    038 */
    039public class AutoCloseInputStream extends ProxyInputStream {
    040
    041    /**
    042     * Creates an automatically closing proxy for the given input stream.
    043     *
    044     * @param in underlying input stream
    045     */
    046    public AutoCloseInputStream(final InputStream in) {
    047        super(in);
    048    }
    049
    050    /**
    051     * Automatically closes the stream if the end of stream was reached.
    052     *
    053     * @param n number of bytes read, or -1 if no more bytes are available
    054     * @throws IOException if the stream could not be closed
    055     * @since 2.0
    056     */
    057    @Override
    058    protected void afterRead(final int n) throws IOException {
    059        if (n == EOF) {
    060            close();
    061        }
    062    }
    063
    064    /**
    065     * Closes the underlying input stream and replaces the reference to it
    066     * with a {@link ClosedInputStream} instance.
    067     * <p>
    068     * This method is automatically called by the read methods when the end
    069     * of input has been reached.
    070     * <p>
    071     * Note that it is safe to call this method any number of times. The original
    072     * underlying input stream is closed and discarded only once when this
    073     * method is first called.
    074     *
    075     * @throws IOException if the underlying input stream can not be closed
    076     */
    077    @Override
    078    public void close() throws IOException {
    079        in.close();
    080        in = ClosedInputStream.INSTANCE;
    081    }
    082
    083    /**
    084     * Ensures that the stream is closed before it gets garbage-collected.
    085     * As mentioned in {@link #close()}, this is a no-op if the stream has
    086     * already been closed.
    087     * @throws Throwable if an error occurs
    088     */
    089    @Override
    090    protected void finalize() throws Throwable {
    091        close();
    092        super.finalize();
    093    }
    094
    095}