org.rakeshv.filters
Class CompressionResponseStream

java.lang.Object
  java.io.OutputStream
      javax.servlet.ServletOutputStream
          org.rakeshv.filters.CompressionResponseStream

All Implemented Interfaces:

java.io.Closeable, java.io.Flushable

public class CompressionResponseStream
extends javax.servlet.ServletOutputStream

A sub-class of ServletOutputStream that is used to compress the response sent by the server to a client request. The only compression method supported are those that are available in the java.util.zip package.

© Copyright 2003, Rakesh Vidyadharan

Version:

$Id: CompressionResponseStream.java,v 1.5 2005/10/15 01:10:20 rakesh Exp $

Author:

Rakesh Vidyadharan 2^nd September 2003

Field Summary

protected boolean	closed Has this stream been closed?
protected int	compressionType The type of compression algorithm to use.
protected java.util.zip.DeflaterOutputStream	deflaterStream The underlying gzip output stream to which we should write data.
protected javax.servlet.ServletOutputStream	output The underlying servlet output stream to which we should write data.
protected javax.servlet.http.HttpServletResponse	response The response with which this servlet output stream is associated.

Constructor Summary

CompressionResponseStream(javax.servlet.http.HttpServletResponse response)
Initialise a new instance of this class with the specified servlet response.

Method Summary

void	close() Close this output stream, causing any buffered data to be flushed and any further output data to throw an IOException.
protected void	createDeflaterStream() Initialise the deflaterStream with the appropriate type of compressed output stream based upon the value in the compressionType instance variable.
void	finish() Finishes writing compressed data to the output stream without closing the underlying stream.
void	flush() Flushes the underlying servlet output stream.
boolean	getClosed() Returns closed.
int	getCompressionType() Returns compressionType.
void	setCompressionType(int compressionType) Set compressionType.
void	write(byte[] buf) Over-ridden to ensure that the method just invokes the write( byte[], int, int ) method.
void	write(byte[] buf, int off, int len) Over-ridden form of the method.
void	write(int value) Over-ridden form of the method.
protected void	writeToDeflater(byte[] buf, int off, int len) Writes the date from the specified byte array to the deflaterStream.
protected void	writeToDeflater(int value) Write the specified value to the deflaterStream.

Methods inherited from class javax.servlet.ServletOutputStream

print, print, print, print, print, print, print, println, println, println, println, println, println, println, println

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

deflaterStream

protected java.util.zip.DeflaterOutputStream deflaterStream

The underlying gzip output stream to which we should write data.

closed

protected boolean closed

Has this stream been closed?

response

protected javax.servlet.http.HttpServletResponse response

The response with which this servlet output stream is associated.

output

protected javax.servlet.ServletOutputStream output

The underlying servlet output stream to which we should write data.

compressionType

protected int compressionType

The type of compression algorithm to use. The supported algorithms are Deflate, GZIP, Zip.

Constructor Detail

CompressionResponseStream

public CompressionResponseStream(javax.servlet.http.HttpServletResponse response)
                          throws java.io.IOException

Initialise a new instance of this class with the specified servlet response.

Parameters:

response - The response to which the contents are to be sent.

Throws:

java.io.IOException

Method Detail

write

public void write(int value)
           throws java.io.IOException

Over-ridden form of the method. Writes the specified int to the deflaterStream if the stream has not been closed. Uses the writeToDeflater( int ) method to write the specified value to the deflaterStream.

Specified by:

write in class java.io.OutputStream

Parameters:

value - - The integer value that is being written.

Throws:

java.io.IOException - - If the stream has already been closed.

writeToDeflater

protected void writeToDeflater(int value)
                        throws java.io.IOException

Write the specified value to the deflaterStream. Checks to ensure that the deflaterStream has been created, and if not, then creates the appropriate instance of the deflaterStream using the compressionType value.

Parameters:

value - - The value to write.

Throws:

java.io.IOException - - If errors are encountered while trying to write to the stream.

write

public void write(byte[] buf)
           throws java.io.IOException

Over-ridden to ensure that the method just invokes the write( byte[], int, int ) method.

Overrides:

write in class java.io.OutputStream

Parameters:

buf - - The byte buffer from which the data is to read and written to the deflaterStream.

Throws:

java.io.IOException - - If errors are encountered while writing to the stream.

write

public void write(byte[] buf,
                  int off,
                  int len)
           throws java.io.IOException

Over-ridden form of the method. Writes the byte array to the deflaterStream using writeToDeflater( byte[], int, int).

Overrides:

write in class java.io.OutputStream

Parameters:

buf - - The byte buffer from which the data is to read and written to the deflaterStream.

off - - The offset from the start of the buffer from which to start reading data.

len - - The length of data that is to be read from the array.

Throws:

java.io.IOException - - If errors are encountered while writing to the stream.

writeToDeflater

protected void writeToDeflater(byte[] buf,
                               int off,
                               int len)
                        throws java.io.IOException

Writes the date from the specified byte array to the deflaterStream. Checks to ensure that the deflaterStream has been created, and if not, then it creates the appropriate instance of the deflaterStream based upon the value of compressionType.

Parameters:

buf - - The byte buffer from which the data is to read and written to the deflaterStream.

off - - The offset from the start of the buffer from which to start reading data.

len - - The length of data that is to be read from the array.

Throws:

java.io.IOException - - If errors are encountered while writing to the stream.

createDeflaterStream

protected void createDeflaterStream()
                             throws java.io.IOException

Initialise the deflaterStream with the appropriate type of compressed output stream based upon the value in the compressionType instance variable. If the value of compressionType does not match one of the following, then Deflate compression is used.

1. CompressionFilter.GZIP_COMPRESSION
2. CompressionFilter.ZIP_COMPRESSION

Note: If zip compression is requested, then the response will contain a ZipEntry object that contains the data as required by the Zip format. The file name for the ZipEntry object is arbitrarily set as the value of System.currentTimeMillis()

.

Throws:

java.io.IOException - - If errors are encountered while creating the stream, or setting its header.

close

public void close()
           throws java.io.IOException

Close this output stream, causing any buffered data to be flushed and any further output data to throw an IOException.

Specified by:

close in interface java.io.Closeable

Overrides:

close in class java.io.OutputStream

Throws:

java.io.IOException - - If the stream has already been closed.

finish

public void finish()
            throws java.io.IOException

Finishes writing compressed data to the output stream without closing the underlying stream. Use this method when applying multiple filters in succession to the same output stream.

Throws:

java.io.IOException - - If errors are encountered while writing to the stream. An exception will be thrown if this method is invoked after the stream has been closed.

flush

public void flush()
           throws java.io.IOException

Flushes the underlying servlet output stream. Flushes any unwritten content in the buffer to the servlet output stream.

Specified by:

flush in interface java.io.Flushable

Overrides:

flush in class java.io.OutputStream

Throws:

java.io.IOException - - If the stream has already been closed.

getClosed

public final boolean getClosed()

Returns closed.

Returns:

boolean - The value/reference of/to closed.

getCompressionType

public final int getCompressionType()

Returns compressionType.

Returns:

int - The value/reference of/to compressionType.

setCompressionType

public final void setCompressionType(int compressionType)

Set compressionType.

Parameters:

compressionType - - The value to set.