org.apache.commons.fileupload
Class DeferredFileOutputStream
public class DeferredFileOutputStream
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.
Version:
- Martin Cooper
private OutputStream | currentOutputStream - The output stream to which data will be written at any given time.
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private FileOutputStream | diskOutputStream - The output stream to which data will be written after the theshold is
reached.
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private ByteArrayOutputStream | memoryOutputStream - The output stream to which data will be written prior to the theshold
being reached.
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private File | outputFile - The file to which output will be directed if the threshold is exceeded.
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DeferredFileOutputStream(int threshold, File outputFile) - Constructs an instance of this class which will trigger an event at the
specified threshold, and save data to a file beyond that point.
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byte[] | getData() - Returns the data for this output stream as an array of bytes, assuming
that the data has been retained in memory.
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File | getFile() - Returns the data for this output stream as a
File , assuming
that the data was written to disk.
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protected OutputStream | getStream() - Returns the current output stream.
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boolean | isInMemory() - Determines whether or not the data for this output stream has been
retained in memory.
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protected void | thresholdReached() - Switches the underlying output stream from a memory based stream to one
that is backed by disk.
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checkThreshold , close , flush , getByteCount , getStream , getThreshold , isThresholdExceeded , thresholdReached , write , write , write |
currentOutputStream
private OutputStream currentOutputStream
The output stream to which data will be written at any given time. This
will always be one of memoryOutputStream
or
diskOutputStream
.
diskOutputStream
private FileOutputStream diskOutputStream
The output stream to which data will be written after the theshold is
reached.
memoryOutputStream
private ByteArrayOutputStream memoryOutputStream
The output stream to which data will be written prior to the theshold
being reached.
outputFile
private File outputFile
The file to which output will be directed if the threshold is exceeded.
DeferredFileOutputStream
public DeferredFileOutputStream(int threshold,
File outputFile)
Constructs an instance of this class which will trigger an event at the
specified threshold, and save data to a file beyond that point.
threshold
- The number of bytes at which to trigger an event.outputFile
- The file to which data is saved beyond the threshold.
getData
public byte[] getData()
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 null
.
- The data for this output stream, or
null
if no such
data is available.
getFile
public File getFile()
Returns the data for this output stream as a File
, assuming
that the data was written to disk. If the data was retained in memory,
this method returns null
.
- The file for this output stream, or
null
if no such
file exists.
getStream
protected OutputStream getStream()
throws IOException
Returns the current output stream. This may be memory based or disk
based, depending on the current state with respect to the threshold.
- getStream in interface ThresholdingOutputStream
- The underlying output stream.
isInMemory
public boolean isInMemory()
Determines whether or not the data for this output stream has been
retained in memory.
true
if the data is available in memory;
false
otherwise.
thresholdReached
protected void thresholdReached()
throws IOException
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.
- thresholdReached in interface ThresholdingOutputStream
Copyright © 2002-2003 Apache Software Foundation. All Rights Reserved.