    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
    024import org.apache.commons.io.build.AbstractStreamBuilder;
    025
    026/**
    027 * Proxy stream that closes and discards the underlying stream as soon as the
    028 * end of input has been reached or when the stream is explicitly closed.
    029 * Not even a reference to the underlying stream is kept after it has been
    030 * closed, so any allocated in-memory buffers can be freed even if the
    031 * client application still keeps a reference to the proxy stream.
    032 * <p>
    033 * This class is typically used to release any resources related to an open
    034 * stream as soon as possible even if the client application (by not explicitly
    035 * closing the stream when no longer needed) or the underlying stream (by not
    036 * releasing resources once the last byte has been read) do not do that.
    037 * </p>
    038 *
    039 * @since 1.4
    040 */
    041public class AutoCloseInputStream extends ProxyInputStream {
    042
    043    /**
    044     * Builds a new {@link AutoCloseInputStream} instance.
    045     * <p>
    046     * For example:
    047     * </p>
    048     *
    049     * <pre>{@code
    050     * AutoCloseInputStream s = AutoCloseInputStream.builder()
    051     *   .setPath(path)
    052     *   .get();}
    053     * </pre>
    054     *
    055     * <pre>{@code
    056     * AutoCloseInputStream s = AutoCloseInputStream.builder()
    057     *   .setInputStream(inputStream)
    058     *   .get();}
    059     * </pre>
    060     *
    061     * @since 2.13.0
    062     */
    063    public static class Builder extends AbstractStreamBuilder<AutoCloseInputStream, Builder> {
    064
    065        /**
    066         * Constructs a new instance.
    067         * <p>
    068         * This builder use the aspect InputStream.
    069         * </p>
    070         *
    071         * @return a new instance.
    072         * @throws IOException              if an I/O error occurs.
    073         * @throws IllegalArgumentException if the buffer is not large enough to hold a complete character.
    074         */
    075        @SuppressWarnings("resource") // Caller closes
    076        @Override
    077        public AutoCloseInputStream get() throws IOException {
    078            return new AutoCloseInputStream(getInputStream());
    079        }
    080
    081    }
    082
    083    /**
    084     * Constructs a new {@link Builder}.
    085     *
    086     * @return a new {@link Builder}.
    087     * @since 2.12.0
    088     */
    089    public static Builder builder() {
    090        return new Builder();
    091    }
    092
    093    /**
    094     * Creates an automatically closing proxy for the given input stream.
    095     *
    096     * @param in underlying input stream
    097     * @deprecated Use {@link #builder()}, {@link Builder}, and {@link Builder#get()}
    098     */
    099    @Deprecated
    100    public AutoCloseInputStream(final InputStream in) {
    101        super(in);
    102    }
    103
    104    /**
    105     * Automatically closes the stream if the end of stream was reached.
    106     *
    107     * @param n number of bytes read, or -1 if no more bytes are available
    108     * @throws IOException if the stream could not be closed
    109     * @since 2.0
    110     */
    111    @Override
    112    protected void afterRead(final int n) throws IOException {
    113        if (n == EOF) {
    114            close();
    115        }
    116    }
    117
    118    /**
    119     * Closes the underlying input stream and replaces the reference to it
    120     * with a {@link ClosedInputStream} instance.
    121     * <p>
    122     * This method is automatically called by the read methods when the end
    123     * of input has been reached.
    124     * <p>
    125     * Note that it is safe to call this method any number of times. The original
    126     * underlying input stream is closed and discarded only once when this
    127     * method is first called.
    128     *
    129     * @throws IOException if the underlying input stream can not be closed
    130     */
    131    @Override
    132    public void close() throws IOException {
    133        in.close();
    134        in = ClosedInputStream.INSTANCE;
    135    }
    136
    137    /**
    138     * Ensures that the stream is closed before it gets garbage-collected.
    139     * As mentioned in {@link #close()}, this is a no-op if the stream has
    140     * already been closed.
    141     * @throws Throwable if an error occurs
    142     */
    143    @Override
    144    protected void finalize() throws Throwable {
    145        close();
    146        super.finalize();
    147    }
    148
    149}