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Apache Commons Exec is a library to reliably execute external processes from within the JVM.
There is a newer version: 1.4.0
/* 
 * Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 */

package org.apache.commons.exec;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import org.apache.commons.exec.util.DebugUtils;

/**
 * Copies all data from an input stream to an output stream.
 *
 * @version $Id: StreamPumper.java 1557263 2014-01-10 21:18:09Z ggregory $
 */
public class StreamPumper implements Runnable {

    /** the default size of the internal buffer for copying the streams */
    private static final int DEFAULT_SIZE = 1024;

    /** the input stream to pump from */
    private final InputStream is;

    /** the output stream to pmp into */
    private final OutputStream os;

    /** the size of the internal buffer for copying the streams */ 
    private final int size;

    /** was the end of the stream reached */
    private boolean finished;

    /** close the output stream when exhausted */
    private final boolean closeWhenExhausted;
    
    /**
     * Create a new stream pumper.
     * 
     * @param is input stream to read data from
     * @param os output stream to write data to.
     * @param closeWhenExhausted if true, the output stream will be closed when the input is exhausted.
     */
    public StreamPumper(final InputStream is, final OutputStream os,
            final boolean closeWhenExhausted) {
        this.is = is;
        this.os = os;
        this.size = DEFAULT_SIZE;
        this.closeWhenExhausted = closeWhenExhausted;
    }

    /**
     * Create a new stream pumper.
     *
     * @param is input stream to read data from
     * @param os output stream to write data to.
     * @param closeWhenExhausted if true, the output stream will be closed when the input is exhausted.
     * @param size the size of the internal buffer for copying the streams
     */
    public StreamPumper(final InputStream is, final OutputStream os,
            final boolean closeWhenExhausted, final int size) {
        this.is = is;
        this.os = os;
        this.size = size > 0 ? size : DEFAULT_SIZE;
        this.closeWhenExhausted = closeWhenExhausted;
    }

    /**
     * Create a new stream pumper.
     * 
     * @param is input stream to read data from
     * @param os output stream to write data to.
     */
    public StreamPumper(final InputStream is, final OutputStream os) {
        this(is, os, false);
    }

    /**
     * Copies data from the input stream to the output stream. Terminates as
     * soon as the input stream is closed or an error occurs.
     */
    public void run() {
        synchronized (this) {
            // Just in case this object is reused in the future
            finished = false;
        }

        final byte[] buf = new byte[this.size];

        int length;
        try {
            while ((length = is.read(buf)) > 0) {
                os.write(buf, 0, length);
            }
        } catch (final Exception e) {
            // nothing to do - happens quite often with watchdog
        } finally {
            if (closeWhenExhausted) {
                try {
                    os.close();
                } catch (final IOException e) {
                    final String msg = "Got exception while closing exhausted output stream";
                    DebugUtils.handleException(msg ,e);
                }
            }
            synchronized (this) {
                finished = true;
                notifyAll();
            }
        }
    }

    /**
     * Tells whether the end of the stream has been reached.
     * 
     * @return true is the stream has been exhausted.
     */
    public synchronized boolean isFinished() {
        return finished;
    }

    /**
     * This method blocks until the stream pumper finishes.
     * 
     * @exception InterruptedException
     *                if any thread interrupted the current thread before or while the current thread was waiting for a
     *                notification.
     * @see #isFinished()
     */
    public synchronized void waitFor() throws InterruptedException {
        while (!isFinished()) {
            wait();
        }
    }
}