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 java.io.InputStream;
020
021/**
022 * Proxy stream that prevents the underlying input stream from being closed.
023 * <p>
024 * This class is typically used in cases where an input stream needs to be
025 * passed to a component that wants to explicitly close the stream even if more
026 * input would still be available to other components.
027 * </p>
028 *
029 * @since 1.4
030 */
031public class CloseShieldInputStream extends ProxyInputStream {
032
033    /**
034     * Constructs a proxy that only shields {@link System#in} from closing.
035     *
036     * @param inputStream the candidate input stream.
037     * @return the given stream or a proxy on {@link System#in}.
038     * @since 2.17.0
039     */
040    public static InputStream systemIn(final InputStream inputStream) {
041        return inputStream == System.in ? wrap(inputStream) : inputStream;
042    }
043
044    /**
045     * Constructs a proxy that shields the given input stream from being closed.
046     *
047     * @param inputStream the input stream to wrap
048     * @return the created proxy
049     * @since 2.9.0
050     */
051    public static CloseShieldInputStream wrap(final InputStream inputStream) {
052        return new CloseShieldInputStream(inputStream);
053    }
054
055    /**
056     * Constructs a proxy that shields the given input stream from being closed.
057     *
058     * @param inputStream underlying input stream
059     * @deprecated Using this constructor prevents IDEs from warning if the
060     *             underlying input stream is never closed. Use
061     *             {@link #wrap(InputStream)} instead.
062     */
063    @Deprecated
064    public CloseShieldInputStream(final InputStream inputStream) {
065        super(inputStream);
066    }
067
068    /**
069     * Replaces the underlying input stream with a {@link ClosedInputStream}
070     * sentinel. The original input stream will remain open, but this proxy will
071     * appear closed.
072     */
073    @Override
074    public void close() {
075        in = ClosedInputStream.INSTANCE;
076    }
077
078}