Enumeration params = request.getParameterNames( );

             while  (params.hasMoreElements( )){

            String paramN = (String) params.nextElement( );
            String paramV = request.getParameter(paramN);
                System.out.println("paramN "+paramN+"="+paramV);
            }

 package  filters;

 import  javax.servlet.*;
 import  javax.servlet.http.HttpSession;
 import  java.io.IOException;
 import  java.util.Enumeration;

/**
 * Created by IntelliJ IDEA.
 * User: oed0nv
 * Date: 01.08.2006
 * Time: 14:28:54
 * To change this template use File | Settings | File Templates.
 */

 public   class  first  implements  Filter {

    String paramN= null ;
    String paramV= null ;

     private  FilterConfig config;


     public   void   init(FilterConfig filterConfig)   throws  ServletException {

         this .config = filterConfig;

    }

     public   void  doFilter(ServletRequest request, ServletResponse response,
                         FilterChain chain)  throws  IOException, ServletException {

     try {
         boolean  rejected = false;

        //************************************************************
        //ПРИЕМ ИЗ ВЫЗЫВАЮЩЕГО МОДУЛЯ

        String KOD_DOK=request.getParameter("KOD_DOK");
        String NOM_DOK=request.getParameter("NOM_DOK");
        NOM_DOK= new String ( NOM_DOK.getBytes("ISO-8859-1"),"Cp1251");
        String DATE_DOK=request.getParameter("DATE_DOK");
        String NAIM_DOK=request.getParameter("NAIM_DOK");
        NAIM_DOK= new String ( NAIM_DOK.getBytes("ISO-8859-1"),"Cp1251");
        String DATE_NACH_OGR=request.getParameter("DATE_NACH_OGR");
        String DATE_OKON_OGR=request.getParameter("DATE_OKON_OGR");
        String PR_KONT=request.getParameter("PR_KONT");
        String KOP=request.getParameter("KOP");
        //************************************************************


        if(KOD_DOK.equals("0")){
            rejected = true;
            reject(request,response,"неуказан код документа!");
            return;
        }
        if(NOM_DOK.length()<10){
            reject(request,response,"неуказан номер документа!");
            return;
        }
        if(NAIM_DOK.length()>256){
            reject(request,response,"краткое название не должно превышать 256 символов!");
            return;
        }
        if(checkDate(DATE_DOK)){
            reject(request,response,"Неверный формат даты! (дата док.)");
            return;

        }
        if(checkDate(DATE_NACH_OGR)){
            reject(request,response,"Неверный формат даты! (дата начала ограничения)");
            return;

        }
        if(checkDate(DATE_OKON_OGR)){
            reject(request,response,"Неверный формат даты! (дата окончания ограничения)");
                   return;
        }
        if(PR_KONT.equals("0")){
            reject(request,response,"неуказана система контроля и управления!");
            return;
        }
        if(KOP.equals("0")){
            reject(request,response,"неуказан код операции!");
            return;
        }


        //Pass the request to its intended destination, if everything
        //is okay
        if (! rejected)
            chain.doFilter(request,response);

    } catch( Exception ex )
        {

            System.out.println ("***Filter first*** Exception.Message: " + ex.getMessage());
        }


    }// doFilter

/*
    private boolean isEmpty(String param){

        if (param == null || param.length( ) < 1){
            return true;
        }

        return false;
    }
*/

    //проверка формата поступившей даты
     private   boolean  checkDate(String s) {
         if (s.length()< 10 ) return  true;
        String good = "0123456789";
         for  (  int  i =  0 ; i < s.length(); i++ ) {
             if  (i== 2 ||i== 5 ){
                 if (s.charAt(i)!='.'){
                     return  true;
                }
                 continue ;
            }
             if  ( good.indexOf(s.charAt(i)) == - 1  )
                 return  true;
        }

         return  false;
    }




     private   void  reject(ServletRequest request, ServletResponse response, String errorMsg)
             throws  IOException, ServletException {

        //Get all the parameter names associated with the form fields
        Enumeration params = request.getParameterNames( );

        paramN =  null ;

        //Create request attributes that the form-related JSP will
        //use to fill in the form fields that have already been
        //filled out correctly. Then the user does not have to fill
        //in the entire form all over again.
         while  (params.hasMoreElements( )){

            paramN = (String) params.nextElement( );

            request.setAttribute( paramN, request.getParameter(paramN));

        }

        //Create an error message; store it in a request attribute
        request.setAttribute("errorMsg",errorMsg);

        //session.setAttribute("errorMsg",errorMsg);


        //Use a RequestDispatcher to return the user to the form in
        //order to fill in the missing values

        RequestDispatcher dispatcher = request.getRequestDispatcher("/base/first.jsp");

        dispatcher.forward(request,response);

    }//reject

     public   void  destroy( ){
        /*called before the Filter instance is removed
   from service by the web container*/
    }

}