    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 end of input has been reached or when the stream is explicitly closed. Not even a
    026 * reference to the underlying stream is kept after it has been closed, so any allocated in-memory buffers can be freed even if the client application still
    027 * keeps a reference to the proxy stream.
    028 * <p>
    029 * This class is typically used to release any resources related to an open stream as soon as possible even if the client application (by not explicitly closing
    030 * the stream when no longer needed) or the underlying stream (by not releasing resources once the last byte has been read) do not do that.
    031 * </p>
    032 * <p>
    033 * To build an instance, use {@link Builder}.
    034 * </p>
    035 *
    036 * @since 1.4
    037 * @see Builder
    038 */
    039public class AutoCloseInputStream extends ProxyInputStream {
    040
    041    // @formatter:off
    042    /**
    043     * Builds a new {@link AutoCloseInputStream} instance.
    044     *
    045     * <p>
    046     * For example:
    047     * </p>
    048     * <pre>{@code
    049     * AutoCloseInputStream s = AutoCloseInputStream.builder()
    050     *   .setPath(path)
    051     *   .get();}
    052     * </pre>
    053     * <pre>{@code
    054     * AutoCloseInputStream s = AutoCloseInputStream.builder()
    055     *   .setInputStream(inputStream)
    056     *   .get();}
    057     * </pre>
    058     *
    059     * @see #get()
    060     * @since 2.13.0
    061     */
    062    // @formatter:on
    063    public static class Builder extends AbstractBuilder<AutoCloseInputStream, Builder> {
    064
    065        /**
    066         * Builds a new {@link AutoCloseInputStream}.
    067         * <p>
    068         * You must set input that supports {@link #getInputStream()}, otherwise, this method throws an exception.
    069         * </p>
    070         * <p>
    071         * This builder use the following aspects:
    072         * </p>
    073         * <ul>
    074         * <li>{@link #getInputStream()}</li>
    075         * </ul>
    076         *
    077         * @return a new instance.
    078         * @throws IllegalStateException         if the {@code origin} is {@code null}.
    079         * @throws UnsupportedOperationException if the origin cannot be converted to an {@link InputStream}.
    080         * @throws IOException                   if an I/O error occurs.
    081         * @see #getInputStream()
    082         */
    083        @Override
    084        public AutoCloseInputStream get() throws IOException {
    085            return new AutoCloseInputStream(this);
    086        }
    087
    088    }
    089
    090    /**
    091     * Constructs a new {@link Builder}.
    092     *
    093     * @return a new {@link Builder}.
    094     * @since 2.12.0
    095     */
    096    public static Builder builder() {
    097        return new Builder();
    098    }
    099
    100    private AutoCloseInputStream(final Builder builder) throws IOException {
    101        super(builder);
    102    }
    103
    104    /**
    105     * Constructs an automatically closing proxy for the given input stream.
    106     *
    107     * @param in underlying input stream
    108     * @deprecated Use {@link #builder()}, {@link Builder}, and {@link Builder#get()}
    109     */
    110    @SuppressWarnings("resource") // ClosedInputStream.nonNull() doesn't allocate
    111    @Deprecated
    112    public AutoCloseInputStream(final InputStream in) {
    113        super(ClosedInputStream.ifNull(in));
    114    }
    115
    116    /**
    117     * Automatically closes the stream if the end of stream was reached.
    118     *
    119     * @param n number of bytes read, or -1 if no more bytes are available
    120     * @throws IOException if the stream could not be closed
    121     * @since 2.0
    122     */
    123    @Override
    124    protected void afterRead(final int n) throws IOException {
    125        if (n == EOF) {
    126            close();
    127        }
    128        super.afterRead(n);
    129    }
    130
    131    /**
    132     * Closes the underlying input stream and replaces the reference to it with a {@link ClosedInputStream} instance.
    133     * <p>
    134     * This method is automatically called by the read methods when the end of input has been reached.
    135     * </p>
    136     * <p>
    137     * Note that it is safe to call this method any number of times. The original underlying input stream is closed and discarded only once when this method is
    138     * first called.
    139     * </p>
    140     *
    141     * @throws IOException if the underlying input stream cannot be closed
    142     */
    143    @Override
    144    public void close() throws IOException {
    145        super.close();
    146        in = ClosedInputStream.INSTANCE;
    147    }
    148
    149    /**
    150     * Ensures that the stream is closed before it gets garbage-collected. As mentioned in {@link #close()}, this is a no-op if the stream has already been
    151     * closed.
    152     *
    153     * @throws Throwable if an error occurs
    154     */
    155    @Override
    156    protected void finalize() throws Throwable {
    157        close();
    158        super.finalize();
    159    }
    160
    161}