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

        if (debug) {
            log("NPNSessionFilter:doFilter()");
        }

        // Create wrappers for the request and response objects.
        // Using these, you can extend the capabilities of the
        // request and response, for example, allow setting parameters
        // on the request before sending the request to the rest of the filter chain,
        // or keep track of the cookies that are set on the response.
        //
        // Caveat: some servers do not handle wrappers very well for forward or
        // include requests.
        RequestWrapper wrappedRequest = new RequestWrapper((HttpServletRequest) request);
        ResponseWrapper wrappedResponse = new ResponseWrapper((HttpServletResponse) response);

        doBeforeProcessing(wrappedRequest, wrappedResponse);

        Throwable problem = null;
        AbstractSiteAccess access = null;
        Connection dbconn = null;
        try {
            //NPN - Check access to protected content
            dbconn =
                    DBConn.getConnection(ServiceLocator.getInstance().
                    getDataSource(DBConn.USANPN_DS_NAME));
            access =
                    new SiteAccessDrupal();
            access.verifyAccess(wrappedRequest, wrappedResponse, dbconn);



                chain.doFilter(wrappedRequest, wrappedResponse);




        } catch (Throwable t) {
            // If an exception is thrown somewhere down the filter chain,
            // we still want to execute our after processing, and then
            // rethrow the problem after that.
            problem = t;
            Logger.getLogger(NPNSessionFilter.class.getName()).log(
                    Level.INFO,
                    t.getLocalizedMessage());

            for(StackTraceElement e : t.getStackTrace()){
                StringBuffer sb = new StringBuffer();
                sb.append(e.getClassName());
                sb.append(":");
                sb.append(e.getFileName());
                sb.append(":");
                sb.append(e.getMethodName());
                sb.append(":");
                sb.append(e.getLineNumber());
                System.out.println(sb.toString());
            }


          }finally{
            DBConn.closeConnection(dbconn);
        }

        doAfterProcessing(wrappedRequest, wrappedResponse);

        // If there was a problem, we want to rethrow it if it is
        // a known type, otherwise log it.
        if (problem != null) {
            if (problem instanceof ServletException) {
                throw (ServletException) problem;
            }
            if (problem instanceof IOException) {
                throw (IOException) problem;
            }
            //NPN - Handle the problem
            if (problem instanceof AccessControlException) {
                try {
                    access.handleAccessProblem(wrappedRequest, wrappedResponse, problem);
                } catch (Exception ex) {
                    Logger.getLogger(NPNSessionFilter.class.getName()).log(Level.SEVERE, null, ex);
                }
                return;

            }
            sendProcessingError(problem, response);
        }
    }