Output stream error, need urgent help

Question

<%@page contentType="text/html" language="java"
         import="java.util.*, java.io.*,
            java.sql.*,
            javax.servlet.*,
            java.lang.*,
            Util.*,
            OJ.*"
%>
<!--Assumes that file name is in the request objects query Parameter -->
<%
     String filename               = "";
     String filepath               = "";
     String filenameDisplay                                                = "";
     //read the file name.
     if( (request.getParameter("downloadFilepath")!=null) || (!((request.getParameter("downloadFilepath")).equals(""))) )
          if(request.getParameter("downloadFilename")==null || (request.getParameter("downloadFilename")).equals(""))
               filename = "";
               filenameDisplay = "DownloadFile";
          else
               filename = request.getParameter("downloadFilename");
               filenameDisplay = filename;
          filepath = request.getParameter("downloadFilepath");
          File f = new File (filepath + filename);
          //set the content type(can be excel/word/powerpoint etc..)
          response.setContentType ("application/octet-stream");
          //set the header and also the Name by which user will be prompted to save
          response.setHeader ("Content-Disposition","attachment;filename=\""+filenameDisplay+"\"");
          InputStream in = new FileInputStream(f);
          ServletOutputStream outs = response.getOutputStream();
          int bit = 256;
          int i = 0;
          try {
               while ((bit) >= 0) {
                    bit = in.read();
                    outs.write(bit);
          catch (IOException ioe) {
          finally{
               outs.flush();
               outs.close();
               in.close();
%>
[\code]
This is what i use to download a file!
This is called from a jsp page using an anchor link (<a href>)
This throws an exception saying "getOutputStream() has already been called for this response"
why? I  have removed all the system outs but still there is an error                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               

Answer 1

heres some servlet code to get you going
if you choose to go that way, not tested
package mywebapp;
import java.io.*;
import java.net.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class DownloadServlet extends HttpServlet {
    public void init(ServletConfig config) throws ServletException {
        super.init(config);
    public void destroy() {
    protected void processRequest(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
        String filename = request.getParameter("downloadFilename");
        String filepath = request.getParameter("downloadFilepath");
        String filenameDisplay;
        // process inputs
        if( (filepath != null) || (!filepath.equals("")) ) {
            if(filename == null || (filename.equals("")) ){
                filename = "";
                filenameDisplay = "DownloadFile";
            else
                filenameDisplay = filename;
            InputStream in = null;
            ServletOutputStream out = null;
            try{
                // read file into byte array
                File f = new File(filepath + filename);
                int size = (int)f.length();
                byte[] ba = new byte[size];
                in = new FileInputStream(f);
                in.read(ba);
                // write out byte array
                response.setContentType("application/octet-stream");
                response.setHeader("Content-Disposition","attachment;filename=\""+filenameDisplay+"\"");
                out = response.getOutputStream();
                out.write(ba);
                out.flush();
            catch (IOException ioe) {
            finally{
                if(out != null)
                    out.close();
                if(in != null)
                    in.close();
        // i assume you have more code to go here
        // else{
    protected void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
        processRequest(request, response);
    protected void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
        processRequest(request, response);
    public String getServletInfo() {
        return "Short description";
}