Can't download a Zip file from Server in GWT

[snajeeb shah]

I am new to GWT, I want to download a zip file stored on Server. At Client side I want to download a file by save as window at button click event.

My client side code is:

String filename = customer.getId();
String url = GWT.getModuleBaseURL() + "FileUploadDownloadServlet?filename=" + filename;
Window.open(url, "_blank", "status=0,toolbar=0,menubar=0,location=0");

My Servlet code is:

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    super.doGet(request, response);

    String filename = request.getParameter("filename");
    if (filename == null) {
        response.sendError(SC_BAD_REQUEST, "Missing file Name");
        return;
    }

   // Load zip file with filename from Backup Directory
    File zipFile = new File(fileBackupPath + File.separator + filename + ".zip");
    File file = new File(zipFile.toString());

    long length = file.length();
    FileInputStream fis = new FileInputStream(file);
    response.addHeader("Content-Disposition","attachment; filename=\"" + filename + "\"");        
    response.setContentType("application/zip");

    if (length > 0 && length <= Integer.MAX_VALUE);
        response.setContentLength((int)length);

    ServletOutputStream out = response.getOutputStream();
    response.setBufferSize(32768);

    int bufSize = response.getBufferSize();
    byte[] buffer = new byte[bufSize];
    BufferedInputStream bis = new BufferedInputStream(fis,bufSize);

    int bytes;
    while ((bytes = bis.read(buffer, 0, bufSize)) >= 0)
        out.write(buffer, 0, bytes);
    bis.close();      
    fis.close();
    out.flush();
    out.close();
}

In my web.xml servlet is defined and mapped as:

  <servlet>
    <servlet-name>ZipFileUploadDownloadServlet</servlet-name>
    <servlet-class>com.xx.xxxxx.server.servlet.FileUploadDownloadServlet</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>ZipFileUploadDownloadServlet</servlet-name>
    <url-pattern>/project/FileUploadDownloadServlet</url-pattern>
  </servlet-mapping>

I get the following error in pop up window:

HTTP Status 500 - Cannot change buffer size after data has been written

[Ankit Garg]

The problem is quite simple, if you see the setBufferSize API Doc, it says you have to set it before setting any response. So call response.setBufferSize before calling response.getOutputStream and you should be fine...