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 *      https://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 */
017
018package org.apache.commons.io.output;
019
020import java.io.IOException;
021import java.io.OutputStream;
022
023import org.apache.commons.io.IOUtils;
024
025/**
026 * Forwards data to a stream that has been associated with this thread.
027 */
028public class DemuxOutputStream extends OutputStream {
029
030    private final InheritableThreadLocal<OutputStream> outputStreamThreadLocal = new InheritableThreadLocal<>();
031
032    /**
033     * Construct a new instance.
034     */
035    public DemuxOutputStream() {
036        // empty
037    }
038
039    /**
040     * Binds the specified stream to the current thread.
041     *
042     * @param output 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 if an error occurs.
055     */
056    @SuppressWarnings("resource") // we actually close the stream here
057    @Override
058    public void close() throws IOException {
059        IOUtils.close(outputStreamThreadLocal.get());
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() throws IOException {
069        @SuppressWarnings("resource")
070        final OutputStream output = outputStreamThreadLocal.get();
071        if (null != output) {
072            output.flush();
073        }
074    }
075
076    /**
077     * Writes byte to stream associated with current thread.
078     *
079     * @param ch the byte to write to stream.
080     * @throws IOException if an error occurs.
081     */
082    @Override
083    public void write(final int ch) throws IOException {
084        @SuppressWarnings("resource")
085        final OutputStream output = outputStreamThreadLocal.get();
086        if (null != output) {
087            output.write(ch);
088        }
089    }
090}