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 * Data written to this stream is forwarded to a stream that has been associated
024 * with this thread.
025 *
026 * @version $Id: DemuxOutputStream.java 1302056 2012-03-18 03:03:38Z ggregory $
027 */
028public class DemuxOutputStream
029    extends OutputStream
030{
031    private final InheritableThreadLocal<OutputStream> m_streams = new InheritableThreadLocal<OutputStream>();
032
033    /**
034     * Bind the specified stream to the current thread.
035     *
036     * @param output the stream to bind
037     * @return the OutputStream that was previously active
038     */
039    public OutputStream bindStream( OutputStream output )
040    {
041        OutputStream stream = m_streams.get();
042        m_streams.set( output );
043        return stream;
044    }
045
046    /**
047     * Closes stream associated with current thread.
048     *
049     * @throws IOException if an error occurs
050     */
051    @Override
052    public void close()
053        throws IOException
054    {
055        OutputStream output = m_streams.get();
056        if( null != output )
057        {
058            output.close();
059        }
060    }
061
062    /**
063     * Flushes stream associated with current thread.
064     *
065     * @throws IOException if an error occurs
066     */
067    @Override
068    public void flush()
069        throws IOException
070    {
071        OutputStream output = m_streams.get();
072        if( null != output )
073        {
074            output.flush();
075        }
076    }
077
078    /**
079     * Writes byte to stream associated with current thread.
080     *
081     * @param ch the byte to write to stream
082     * @throws IOException if an error occurs
083     */
084    @Override
085    public void write( int ch )
086        throws IOException
087    {
088        OutputStream output = m_streams.get();
089        if( null != output )
090        {
091            output.write( ch );
092        }
093    }
094}