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