exception 

javax.servlet.ServletException: Servlet execution threw an exception


root cause 

java.lang.NoClassDefFoundError: javax/servlet/ServletInputStream
	org.apache.commons.fileupload.servlet.ServletFileUpload.parseRequest(ServletFileUpload.java: 116 )
	main.uploadfile.doPost(uploadfile.java: 79 )
	javax.servlet.http.HttpServlet.service(HttpServlet.java: 709 )
	javax.servlet.http.HttpServlet.service(HttpServlet.java: 802 )

 import  java.io.File;
 import  java.io.IOException;

 import  javax.servlet.*;
 import  javax.servlet.http.*;
 import  java.io.*;
 import  java.util.*;

 import  org.apache.commons.fileupload.servlet.ServletFileUpload;
 import  org.apache.commons.fileupload.FileItem;
 import  org.apache.commons.fileupload.FileItemFactory;
 import  org.apache.commons.fileupload.FileUpload;
 import  org.apache.commons.fileupload.FileUploadException;

...

  ServletFileUpload upload =  new  ServletFileUpload();

  // Parse the request
  List items = upload.parseRequest(request); // строчка номер 79

...

 package  org.apache.commons.fileupload.servlet;

 import  java.util.List;
 import  javax.servlet.http.HttpServletRequest;
 import  org.apache.commons.fileupload.FileItemFactory;
 import  org.apache.commons.fileupload.FileUpload;
 import  org.apache.commons.fileupload.FileUploadException;

...

    /**
     * Processes an <a href="http://www.ietf.org/rfc/rfc1867.txt">RFC 1867</a>
     * compliant <code>multipart/form-data</code> stream.
     *
     * @param request The servlet request to be parsed.
     *
     * @return A list of <code>FileItem</code> instances parsed from the
     *         request, in the order that they were transmitted.
     *
     * @throws FileUploadException if there are problems reading/parsing
     *                             the request or storing files.
     */
     public  List /* FileItem */ parseRequest(HttpServletRequest request)
             throws  FileUploadException {
         return  parseRequest( new  ServletRequestContext(request));
    }