    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}