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