    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 *      https://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         * Constructs a new builder of {@link AutoCloseInputStream}.
    067         */
    068        public Builder() {
    069            // empty
    070        }
    071
    072        /**
    073         * Builds a new {@link AutoCloseInputStream}.
    074         * <p>
    075         * You must set an aspect that supports {@link #getInputStream()}, otherwise, this method throws an exception.
    076         * </p>
    077         * <p>
    078         * This builder uses the following aspects:
    079         * </p>
    080         * <ul>
    081         * <li>{@link #getInputStream()} gets the target aspect.</li>
    082         * </ul>
    083         *
    084         * @return a new instance.
    085         * @throws IllegalStateException         if the {@code origin} is {@code null}.
    086         * @throws UnsupportedOperationException if the origin cannot be converted to an {@link InputStream}.
    087         * @throws IOException                   if an I/O error occurs converting to an {@link InputStream} using {@link #getInputStream()}.
    088         * @see #getInputStream()
    089         * @see #getUnchecked()
    090         */
    091        @Override
    092        public AutoCloseInputStream get() throws IOException {
    093            return new AutoCloseInputStream(this);
    094        }
    095
    096    }
    097
    098    /**
    099     * Constructs a new {@link Builder}.
    100     *
    101     * @return a new {@link Builder}.
    102     * @since 2.12.0
    103     */
    104    public static Builder builder() {
    105        return new Builder();
    106    }
    107
    108    private AutoCloseInputStream(final Builder builder) throws IOException {
    109        super(builder);
    110    }
    111
    112    /**
    113     * Constructs an automatically closing proxy for the given input stream.
    114     *
    115     * @param in underlying input stream.
    116     * @deprecated Use {@link #builder()}, {@link Builder}, and {@link Builder#get()}
    117     */
    118    @SuppressWarnings("resource") // ClosedInputStream.nonNull() doesn't allocate
    119    @Deprecated
    120    public AutoCloseInputStream(final InputStream in) {
    121        super(ClosedInputStream.ifNull(in));
    122    }
    123
    124    /**
    125     * Automatically closes the stream if the end of stream was reached.
    126     *
    127     * @param n number of bytes read, or -1 if no more bytes are available.
    128     * @throws IOException if the stream could not be closed.
    129     * @since 2.0
    130     */
    131    @Override
    132    protected void afterRead(final int n) throws IOException {
    133        if (n == EOF) {
    134            close();
    135        }
    136        super.afterRead(n);
    137    }
    138
    139    /**
    140     * Closes the underlying input stream and replaces the reference to it with a {@link ClosedInputStream} instance.
    141     * <p>
    142     * This method is automatically called by the read methods when the end of input has been reached.
    143     * </p>
    144     * <p>
    145     * 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
    146     * first called.
    147     * </p>
    148     *
    149     * @throws IOException if the underlying input stream cannot be closed.
    150     */
    151    @Override
    152    public void close() throws IOException {
    153        super.close();
    154        in = ClosedInputStream.INSTANCE;
    155    }
    156
    157    /**
    158     * 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
    159     * closed.
    160     *
    161     * @throws Throwable if an error occurs.
    162     */
    163    @Override
    164    protected void finalize() throws Throwable {
    165        close();
    166        super.finalize();
    167    }
    168
    169}