Java EE (Java Enterprise Edition) General Discussion

I have been trying to work on a servlet that can handle file uploads..
I have downloaded the commons fileupload API from the jakarta.apache.org site..

i copied the jar file to my jdk\jre\lib\ext directory and jdk\lib\..
I m using netbeans5.0 rc2 as my editor..

Then i made a new servlet file with the following code..

 import java.io.*;
import java.net.*;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;

import org.apache.commons.fileupload.*;
import org.apache.commons.fileupload.disk.*;
import org.apache.commons.fileupload.servlet.*;

import javax.servlet.*;
import javax.servlet.http.*;

public class fileuploadservlet2 extends HttpServlet {

 protected void doPost(HttpServletRequest req, HttpServletResponse response)
    throws ServletException, IOException {
       
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        
        out.println("</html>");
         DiskFileItemFactory factory = new DiskFileItemFactory();

        factory.setSizeThreshold(4096);
      
        factory.setRepository(new File("/tmp"));

        ServletFileUpload upload = new ServletFileUpload(factory);
     
        upload.setSizeMax(1000000);
      
        List fileItems=null;
        
        
       try
       {
           fileItems = upload.parseRequest(req);
       }catch(FileUploadException e)
       {
            out.println("Exception Raised:"+e);
       }
        
        Iterator i = fileItems.iterator();
        String comment = ((FileItem)i.next()).getString();
        FileItem fi = (FileItem)i.next();
         String fileName = fi.getName();
        try
        {
            fi.write(new File("/", fileName));
        }catch(Exception e)
        {
            out.println("Exception Raised:"+e);
        }
        out.close();
    }
public String getServletInfo() {
        return "Short description";
    }
}

this is getting compiled..but at runtime i m getting strange errors with apache tomcat 5.5 which is bundled with Netbeans..

it says a class not found exception..

javax.servlet.ServletException: Servlet execution threw an exception
org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:362)

root cause :
java.lang.NoClassDefFoundError: javax/servlet/ServletInputStream
org.apache.commons.fileupload.servlet.ServletFileUpload.parseRequest(ServletFileUpload.java:116)
fileuploadservlet2.doPost(fileuploadservlet2.java:86)
javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:362)

i cant understand why this type of exception is occuring...Why cant it find the javax.servlet.ServletInputStream Class....is there anything wrong in the commons fileupload API???

please help..thanks in advance..