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 */
027public class DemuxOutputStream extends OutputStream {
028
029    private final InheritableThreadLocal<OutputStream> outputStreamThreadLocal = new InheritableThreadLocal<>();
030
031    /**
032     * Construct a new instance.
033     */
034    public DemuxOutputStream() {
035        // empty
036    }
037
038    /**
039     * Binds the specified stream to the current thread.
040     *
041     * @param output
042     *            the stream to bind
043     * @return the OutputStream that was previously active
044     */
045    public OutputStream bindStream(final OutputStream output) {
046        final OutputStream stream = outputStreamThreadLocal.get();
047        outputStreamThreadLocal.set(output);
048        return stream;
049    }
050
051    /**
052     * Closes stream associated with current thread.
053     *
054     * @throws IOException
055     *             if an error occurs
056     */
057    @SuppressWarnings("resource") // we actually close the stream here
058    @Override
059    public void close() throws IOException {
060        IOUtils.close(outputStreamThreadLocal.get());
061    }
062
063    /**
064     * Flushes stream associated with current thread.
065     *
066     * @throws IOException
067     *             if an error occurs
068     */
069    @Override
070    public void flush() throws IOException {
071        @SuppressWarnings("resource")
072        final OutputStream output = outputStreamThreadLocal.get();
073        if (null != output) {
074            output.flush();
075        }
076    }
077
078    /**
079     * Writes byte to stream associated with current thread.
080     *
081     * @param ch
082     *            the byte to write to stream
083     * @throws IOException
084     *             if an error occurs
085     */
086    @Override
087    public void write(final int ch) throws IOException {
088        @SuppressWarnings("resource")
089        final OutputStream output = outputStreamThreadLocal.get();
090        if (null != output) {
091            output.write(ch);
092        }
093    }
094}