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/*
* 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.tomcat.util.http.fileupload;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
/**
* <p>An output stream which will retain data in memory until a specified
* threshold is reached, and only then commit it to disk. If the stream is
* closed before the threshold is reached, the data will not be written to
* disk at all.</p>
*
* @author <a href="mailto:martinc@apache.org">Martin Cooper</a>
*
*
*/
public class DeferredFileOutputStream
extends ThresholdingOutputStream
{
// ----------------------------------------------------------- Data members
/**
* The output stream to which data will be written prior to the theshold
* being reached.
*/
private ByteArrayOutputStream memoryOutputStream;
/**
* The output stream to which data will be written after the theshold is
* reached.
*/
private FileOutputStream diskOutputStream;
/**
* The output stream to which data will be written at any given time. This
* will always be one of <code>memoryOutputStream</code> or
* <code>diskOutputStream</code>.
*/
private OutputStream currentOutputStream;
/**
* The file to which output will be directed if the threshold is exceeded.
*/
private File outputFile;
// ----------------------------------------------------------- Constructors
/**
* Constructs an instance of this class which will trigger an event at the
* specified threshold, and save data to a file beyond that point.
*
* @param threshold The number of bytes at which to trigger an event.
* @param outputFile The file to which data is saved beyond the threshold.
*/
public DeferredFileOutputStream(int threshold, File outputFile)
{
super(threshold);
this.outputFile = outputFile;
if (threshold < DefaultFileItemFactory.DEFAULT_SIZE_THRESHOLD) {
// Small threshold, use it
memoryOutputStream = new ByteArrayOutputStream(threshold);
} else {
// Large threshold. Use default and array will expand if required
memoryOutputStream = new ByteArrayOutputStream(
DefaultFileItemFactory.DEFAULT_SIZE_THRESHOLD);
}
currentOutputStream = memoryOutputStream;
}
// --------------------------------------- ThresholdingOutputStream methods
/**
* Returns the current output stream. This may be memory based or disk
* based, depending on the current state with respect to the threshold.
*
* @return The underlying output stream.
*
* @exception IOException if an error occurs.
*/
protected OutputStream getStream() throws IOException
{
return currentOutputStream;
}
/**
* Switches the underlying output stream from a memory based stream to one
* that is backed by disk. This is the point at which we realise that too
* much data is being written to keep in memory, so we elect to switch to
* disk-based storage.
*
* @exception IOException if an error occurs.
*/
protected void thresholdReached() throws IOException
{
byte[] data = memoryOutputStream.toByteArray();
FileOutputStream fos = new FileOutputStream(outputFile);
fos.write(data);
diskOutputStream = fos;
currentOutputStream = fos;
memoryOutputStream = null;
}
// --------------------------------------------------------- Public methods
/**
* Determines whether or not the data for this output stream has been
* retained in memory.
*
* @return <code>true</code> if the data is available in memory;
* <code>false</code> otherwise.
*/
public boolean isInMemory()
{
return (!isThresholdExceeded());
}
/**
* Returns the data for this output stream as an array of bytes, assuming
* that the data has been retained in memory. If the data was written to
* disk, this method returns <code>null</code>.
*
* @return The data for this output stream, or <code>null</code> if no such
* data is available.
*/
public byte[] getData()
{
if (memoryOutputStream != null)
{
return memoryOutputStream.toByteArray();
}
return null;
}
/**
* Returns the data for this output stream as a <code>File</code>, assuming
* that the data was written to disk. If the data was retained in memory,
* this method returns <code>null</code>.
*
* @return The file for this output stream, or <code>null</code> if no such
* file exists.
*/
public File getFile()
{
return outputFile;
}
}
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