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CompressionResponseStream.javaAPI DocGlassfish v2 API9930Fri May 04 22:34:12 BST 2007compressionFilters

CompressionResponseStream.java


/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 * 
 * Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
 * 
 * Portions Copyright Apache Software Foundation.
 * 
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License. You can obtain
 * a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
 * or glassfish/bootstrap/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
 * 
 * When distributing the software, include this License Header Notice in each
 * file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
 * Sun designates this particular file as subject to the "Classpath" exception
 * as provided by Sun in the GPL Version 2 section of the License file that
 * accompanied this code.  If applicable, add the following below the License
 * Header, with the fields enclosed by brackets [] replaced by your own
 * identifying information: "Portions Copyrighted [year]
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 * 
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 * only the GPL Version 2, indicate your decision by adding "[Contributor]
 * elects to include this software in this distribution under the [CDDL or GPL
 * Version 2] license."  If you don't indicate a single choice of license, a
 * recipient has the option to distribute your version of this file under
 * either the CDDL, the GPL Version 2 or to extend the choice of license to
 * its licensees as provided above.  However, if you add GPL Version 2 code
 * and therefore, elected the GPL Version 2 license, then the option applies
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 * holder.
 */

package compressionFilters;

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: 2007/05/05 05:34:11 $
 */

public class CompressionResponseStream
    extends ServletOutputStream {


    // ----------------------------------------------------------- Constructors


    /**
     * 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();

    }


    // ----------------------------------------------------- Instance Variables


    /**
     * 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;


    // --------------------------------------------------------- Public Methods

    /**
     * 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");
            }
            gzipstream = new GZIPOutputStream(output);
            response.addHeader("Content-Encoding", "gzip");
        }
        gzipstream.write(b, off, len);

    }


    // -------------------------------------------------------- Package Methods


    /**
     * Has this response stream been closed?
     */
    public boolean closed() {

        return (this.closed);

    }

}