    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    private final InheritableThreadLocal<OutputStream> outputStreamThreadLocal = new InheritableThreadLocal<>();
    029
    030    /**
    031     * Binds the specified stream to the current thread.
    032     *
    033     * @param output
    034     *            the stream to bind
    035     * @return the OutputStream that was previously active
    036     */
    037    public OutputStream bindStream(final OutputStream output) {
    038        final OutputStream stream = outputStreamThreadLocal.get();
    039        outputStreamThreadLocal.set(output);
    040        return stream;
    041    }
    042
    043    /**
    044     * Closes stream associated with current thread.
    045     *
    046     * @throws IOException
    047     *             if an error occurs
    048     */
    049    @SuppressWarnings("resource") // we actually close the stream here
    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}