GZIP Filter, response stream and Response Wrapper : GZIP « File Input Output « Java

1. Java
2. File Input Output
3. GZIP

GZIP Filter, response stream and Response Wrapper

 
/*
 * Copyright 2003 Jayson Falkner (jayson@jspinsider.com)
 * This code is from "Servlets and JavaServer pages; the J2EE Web Tier",
 * http://www.jspbook.com. You may freely use the code both commercially
 * and non-commercially. If you like the code, please pick up a copy of
 * the book and help support the authors, development of more free code,
 * and the JSP/Servlet/J2EE community.
 */

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.util.zip.GZIPOutputStream;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;

public class GZIPFilter implements Filter {

  public void doFilter(ServletRequest req, ServletResponse res,
      FilterChain chain) throws IOException, ServletException {
    if (req instanceof HttpServletRequest) {
      HttpServletRequest request = (HttpServletRequest) req;
      HttpServletResponse response = (HttpServletResponse) res;
      String ae = request.getHeader("accept-encoding");
      if (ae != null && ae.indexOf("gzip") != -1) {        
        GZIPResponseWrapper wrappedResponse = new GZIPResponseWrapper(response);
        chain.doFilter(req, wrappedResponse);
        wrappedResponse.finishResponse();
        return;
      }
      chain.doFilter(req, res);
    }
  }

  public void init(FilterConfig filterConfig) {
    // noop
  }

  public void destroy() {
    // noop
  }
}
/*
 * Copyright 2003 Jayson Falkner (jayson@jspinsider.com)
 * This code is from "Servlets and JavaServer pages; the J2EE Web Tier",
 * http://www.jspbook.com. You may freely use the code both commercially
 * and non-commercially. If you like the code, please pick up a copy of
 * the book and help support the authors, development of more free code,
 * and the JSP/Servlet/J2EE community.
 */
class GZIPResponseStream extends ServletOutputStream { 
  protected ByteArrayOutputStream baos = null;
  protected GZIPOutputStream gzipstream = null;
  protected boolean closed = false;
  protected HttpServletResponse response = null;
  protected ServletOutputStream output = null;

  public GZIPResponseStream(HttpServletResponse response) throws IOException {
    super();
    closed = false;
    this.response = response;
    this.output = response.getOutputStream();
    baos = new ByteArrayOutputStream();
    gzipstream = new GZIPOutputStream(baos);
  }

  public void close() throws IOException {
    if (closed) {
      throw new IOException("This output stream has already been closed");
    }
    gzipstream.finish();

    byte[] bytes = baos.toByteArray();


    response.addHeader("Content-Length", 
                       Integer.toString(bytes.length)); 
    response.addHeader("Content-Encoding", "gzip");
    output.write(bytes);
    output.flush();
    output.close();
    closed = true;
  }

  public void flush() throws IOException {
    if (closed) {
      throw new IOException("Cannot flush a closed output stream");
    }
    gzipstream.flush();
  }

  public void write(int b) throws IOException {
    if (closed) {
      throw new IOException("Cannot write to a closed output stream");
    }
    gzipstream.write((byte)b);
  }

  public void write(byte b[]) throws IOException {
    write(b, 0, b.length);
  }

  public void write(byte b[], int off, int len) throws IOException {
    if (closed) {
      throw new IOException("Cannot write to a closed output stream");
    }
    gzipstream.write(b, off, len);
  }

  public boolean closed() {
    return (this.closed);
  }
  
  public void reset() {
    //noop
  }
}

/*
 * Copyright 2003 Jayson Falkner (jayson@jspinsider.com)
 * This code is from "Servlets and JavaServer pages; the J2EE Web Tier",
 * http://www.jspbook.com. You may freely use the code both commercially
 * and non-commercially. If you like the code, please pick up a copy of
 * the book and help support the authors, development of more free code,
 * and the JSP/Servlet/J2EE community.
 */
 class GZIPResponseWrapper extends HttpServletResponseWrapper {
  protected HttpServletResponse origResponse = null;
  protected ServletOutputStream stream = null;
  protected PrintWriter writer = null;

  public GZIPResponseWrapper(HttpServletResponse response) {
    super(response);
    origResponse = response;
  }

  public ServletOutputStream createOutputStream() throws IOException {
    return (new GZIPResponseStream(origResponse));
  }

  public void finishResponse() {
    try {
      if (writer != null) {
        writer.close();
      } else {
        if (stream != null) {
          stream.close();
        }
      }
    } catch (IOException e) {}
  }

  public void flushBuffer() throws IOException {
    stream.flush();
  }

  public ServletOutputStream getOutputStream() throws IOException {
    if (writer != null) {
      throw new IllegalStateException("getWriter() has already been called!");
    }

    if (stream == null)
      stream = createOutputStream();
    return (stream);
  }

  public PrintWriter getWriter() throws IOException {
    if (writer != null) {
      return (writer);
    }

    if (stream != null) {
      throw new IllegalStateException("getOutputStream() has already been called!");
    }

   stream = createOutputStream();
   writer = new PrintWriter(new OutputStreamWriter(stream, "UTF-8"));
   return (writer);
  }

  public void setContentLength(int length) {}
}

   
  

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