Compression Response Stream servlets
/*
* Copyright 2004 The Apache Software Foundation
*
* Licensed 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.
*/
import java.io.IOException;
import java.io.OutputStream;
import java.util.zip.GZIPOutputStream;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletResponse;
/**
* Implementation of <b>ServletOutputStream</b> that works with
* the CompressionServletResponseWrapper implementation.
*
* @author Amy Roh
* @author Dmitri Valdin
* @version $Revision: 1.3 $, $Date: 2004/03/18 16:40:33 $
*/
public class CompressionResponseStream
extends ServletOutputStream {
/**
* Construct a servlet output stream associated with the specified Response.
*
* @param response The associated response
*/
public CompressionResponseStream(HttpServletResponse response) throws IOException{
super();
closed = false;
this.response = response;
this.output = response.getOutputStream();
}
/**
* The threshold number which decides to compress or not.
* Users can configure in web.xml to set it to fit their needs.
*/
protected int compressionThreshold = 0;
/**
* Debug level
*/
private int debug = 0;
/**
* The buffer through which all of our output bytes are passed.
*/
protected byte[] buffer = null;
/**
* The number of data bytes currently in the buffer.
*/
protected int bufferCount = 0;
/**
* The underlying gzip output stream to which we should write data.
*/
protected GZIPOutputStream gzipstream = null;
/**
* Has this stream been closed?
*/
protected boolean closed = false;
/**
* The content length past which we will not write, or -1 if there is
* no defined content length.
*/
protected int length = -1;
/**
* The response with which this servlet output stream is associated.
*/
protected HttpServletResponse response = null;
/**
* The underlying servket output stream to which we should write data.
*/
protected ServletOutputStream output = null;
/**
* Set debug level
*/
public void setDebugLevel(int debug) {
this.debug = debug;
}
/**
* Set the compressionThreshold number and create buffer for this size
*/
protected void setBuffer(int threshold) {
compressionThreshold = threshold;
buffer = new byte[compressionThreshold];
if (debug > 1) {
System.out.println("buffer is set to "+compressionThreshold);
}
}
/**
* Close this output stream, causing any buffered data to be flushed and
* any further output data to throw an IOException.
*/
public void close() throws IOException {
if (debug > 1) {
System.out.println("close() @ CompressionResponseStream");
}
if (closed)
throw new IOException("This output stream has already been closed");
if (gzipstream != null) {
flushToGZip();
gzipstream.close();
gzipstream = null;
} else {
if (bufferCount > 0) {
if (debug > 2) {
System.out.print("output.write(");
System.out.write(buffer, 0, bufferCount);
System.out.println(")");
}
output.write(buffer, 0, bufferCount);
bufferCount = 0;
}
}
output.close();
closed = true;
}
/**
* Flush any buffered data for this output stream, which also causes the
* response to be committed.
*/
public void flush() throws IOException {
if (debug > 1) {
System.out.println("flush() @ CompressionResponseStream");
}
if (closed) {
throw new IOException("Cannot flush a closed output stream");
}
if (gzipstream != null) {
gzipstream.flush();
}
}
public void flushToGZip() throws IOException {
if (debug > 1) {
System.out.println("flushToGZip() @ CompressionResponseStream");
}
if (bufferCount > 0) {
if (debug > 1) {
System.out.println("flushing out to GZipStream, bufferCount = " + bufferCount);
}
writeToGZip(buffer, 0, bufferCount);
bufferCount = 0;
}
}
/**
* Write the specified byte to our output stream.
*
* @param b The byte to be written
*
* @exception IOException if an input/output error occurs
*/
public void write(int b) throws IOException {
if (debug > 1) {
System.out.println("write "+b+" in CompressionResponseStream ");
}
if (closed)
throw new IOException("Cannot write to a closed output stream");
if (bufferCount >= buffer.length) {
flushToGZip();
}
buffer[bufferCount++] = (byte) b;
}
/**
* Write <code>b.length</code> bytes from the specified byte array
* to our output stream.
*
* @param b The byte array to be written
*
* @exception IOException if an input/output error occurs
*/
public void write(byte b[]) throws IOException {
write(b, 0, b.length);
}
/**
* Write <code>len</code> bytes from the specified byte array, starting
* at the specified offset, to our output stream.
*
* @param b The byte array containing the bytes to be written
* @param off Zero-relative starting offset of the bytes to be written
* @param len The number of bytes to be written
*
* @exception IOException if an input/output error occurs
*/
public void write(byte b[], int off, int len) throws IOException {
if (debug > 1) {
System.out.println("write, bufferCount = " + bufferCount + " len = " + len + " off = " + off);
}
if (debug > 2) {
System.out.print("write(");
System.out.write(b, off, len);
System.out.println(")");
}
if (closed)
throw new IOException("Cannot write to a closed output stream");
if (len == 0)
return;
// Can we write into buffer ?
if (len <= (buffer.length - bufferCount)) {
System.arraycopy(b, off, buffer, bufferCount, len);
bufferCount += len;
return;
}
// There is not enough space in buffer. Flush it ...
flushToGZip();
// ... and try again. Note, that bufferCount = 0 here !
if (len <= (buffer.length - bufferCount)) {
System.arraycopy(b, off, buffer, bufferCount, len);
bufferCount += len;
return;
}
// write direct to gzip
writeToGZip(b, off, len);
}
public void writeToGZip(byte b[], int off, int len) throws IOException {
if (debug > 1) {
System.out.println("writeToGZip, len = " + len);
}
if (debug > 2) {
System.out.print("writeToGZip(");
System.out.write(b, off, len);
System.out.println(")");
}
if (gzipstream == null) {
if (debug > 1) {
System.out.println("new GZIPOutputStream");
}
response.addHeader("Content-Encoding", "gzip");
gzipstream = new GZIPOutputStream(output);
}
gzipstream.write(b, off, len);
}
// -------------------------------------------------------- Package Methods
/**
* Has this response stream been closed?
*/
public boolean closed() {
return (this.closed);
}
}
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