org.apache.tomcat.util.http.fileupload

Class DeferredFileOutputStream

public class DeferredFileOutputStream extends ThresholdingOutputStream

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: $Id: DeferredFileOutputStream.java 711597 2008-11-05 16:09:26Z markt $

Author: Martin Cooper

Constructor Summary
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.
Method Summary
byte[]getData()
Returns the data for this output stream as an array of bytes, assuming that the data has been retained in memory.
FilegetFile()
Returns the data for this output stream as a File, assuming that the data was written to disk.
protected OutputStreamgetStream()
Returns the current output stream.
booleanisInMemory()
Determines whether or not the data for this output stream has been retained in memory.
protected voidthresholdReached()
Switches the underlying output stream from a memory based stream to one that is backed by disk.

Constructor Detail

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.

Parameters: threshold The number of bytes at which to trigger an event. outputFile The file to which data is saved beyond the threshold.

Method Detail

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.

Returns: 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.

Returns: The file for this output stream, or null if no such file exists.

getStream

protected OutputStream getStream()
Returns the current output stream. This may be memory based or disk based, depending on the current state with respect to the threshold.

Returns: The underlying output stream.

Throws: IOException if an error occurs.

isInMemory

public boolean isInMemory()
Determines whether or not the data for this output stream has been retained in memory.

Returns: true if the data is available in memory; false otherwise.

thresholdReached

protected void thresholdReached()
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.

Throws: IOException if an error occurs.

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