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.output;
018
019import java.io.IOException;
020import java.io.OutputStream;
021
022/**
023 * Forwards data to a stream that has been associated with this thread.
024 *
025 */
026public class DemuxOutputStream extends OutputStream {
027    private final InheritableThreadLocal<OutputStream> outputStreamThreadLocal = new InheritableThreadLocal<>();
028
029    /**
030     * Binds the specified stream to the current thread.
031     *
032     * @param output
033     *            the stream to bind
034     * @return the OutputStream that was previously active
035     */
036    public OutputStream bindStream(final OutputStream output) {
037        final OutputStream stream = outputStreamThreadLocal.get();
038        outputStreamThreadLocal.set(output);
039        return stream;
040    }
041
042    /**
043     * Closes stream associated with current thread.
044     *
045     * @throws IOException
046     *             if an error occurs
047     */
048    @Override
049    public void close() throws IOException {
050        final OutputStream output = outputStreamThreadLocal.get();
051        if (null != output) {
052            output.close();
053        }
054    }
055
056    /**
057     * Flushes stream associated with current thread.
058     *
059     * @throws IOException
060     *             if an error occurs
061     */
062    @Override
063    public void flush() throws IOException {
064        @SuppressWarnings("resource")
065        final OutputStream output = outputStreamThreadLocal.get();
066        if (null != output) {
067            output.flush();
068        }
069    }
070
071    /**
072     * Writes byte to stream associated with current thread.
073     *
074     * @param ch
075     *            the byte to write to stream
076     * @throws IOException
077     *             if an error occurs
078     */
079    @Override
080    public void write(final int ch) throws IOException {
081        @SuppressWarnings("resource")
082        final OutputStream output = outputStreamThreadLocal.get();
083        if (null != output) {
084            output.write(ch);
085        }
086    }
087}