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      1 /*
      2  * Licensed to the Apache Software Foundation (ASF) under one or more
      3  * contributor license agreements.  See the NOTICE file distributed with
      4  * this work for additional information regarding copyright ownership.
      5  * The ASF licenses this file to You under the Apache License, Version 2.0
      6  * (the "License"); you may not use this file except in compliance with
      7  * the License.  You may obtain a copy of the License at
      8  *
      9  *      http://www.apache.org/licenses/LICENSE-2.0
     10  *
     11  * Unless required by applicable law or agreed to in writing, software
     12  * distributed under the License is distributed on an "AS IS" BASIS,
     13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     14  * See the License for the specific language governing permissions and
     15  * limitations under the License.
     16  */
     17 package org.apache.commons.io.output;
     18 
     19 import java.io.IOException;
     20 import java.io.OutputStream;
     21 
     22 /**
     23  * Data written to this stream is forwarded to a stream that has been associated
     24  * with this thread.
     25  *
     26  * @author <a href="mailto:peter (at) apache.org">Peter Donald</a>
     27  * @version $Revision: 437567 $ $Date: 2006-08-28 07:39:07 +0100 (Mon, 28 Aug 2006) $
     28  */
     29 public class DemuxOutputStream
     30     extends OutputStream
     31 {
     32     private InheritableThreadLocal<OutputStream> m_streams = new InheritableThreadLocal<OutputStream>();
     33 
     34     /**
     35      * Bind the specified stream to the current thread.
     36      *
     37      * @param output the stream to bind
     38      * @return the OutputStream that was previously active
     39      */
     40     public OutputStream bindStream( OutputStream output )
     41     {
     42         OutputStream stream = getStream();
     43         m_streams.set( output );
     44         return stream;
     45     }
     46 
     47     /**
     48      * Closes stream associated with current thread.
     49      *
     50      * @throws IOException if an error occurs
     51      */
     52     @Override
     53     public void close()
     54         throws IOException
     55     {
     56         OutputStream output = getStream();
     57         if( null != output )
     58         {
     59             output.close();
     60         }
     61     }
     62 
     63     /**
     64      * Flushes stream associated with current thread.
     65      *
     66      * @throws IOException if an error occurs
     67      */
     68     @Override
     69     public void flush()
     70         throws IOException
     71     {
     72         OutputStream output = getStream();
     73         if( null != output )
     74         {
     75             output.flush();
     76         }
     77     }
     78 
     79     /**
     80      * Writes byte to stream associated with current thread.
     81      *
     82      * @param ch the byte to write to stream
     83      * @throws IOException if an error occurs
     84      */
     85     @Override
     86     public void write( int ch )
     87         throws IOException
     88     {
     89         OutputStream output = getStream();
     90         if( null != output )
     91         {
     92             output.write( ch );
     93         }
     94     }
     95 
     96     /**
     97      * Utility method to retrieve stream bound to current thread (if any).
     98      *
     99      * @return the output stream
    100      */
    101     private OutputStream getStream()
    102     {
    103         return m_streams.get();
    104     }
    105 }
    106