Acegi onSuccessfulAuthentication

Some time back, I raised a jira in Acegi, which was turned down. There was no adequate response from spring team. Here I am writing about it, so other spring users (read gurus) may pitch in.

//Edited to short and precise
protected void successfulAuthentication(HttpServletRequest request,
    HttpServletResponse response, Authentication authResult)
    throws IOException {

    SecurityContextHolder.getContext().setAuthentication(authResult);

    String targetUrl = (String) request.getSession()
                 .getAttribute(ACEGI_SECURITY_TARGET_URL_KEY);
    request.getSession().removeAttribute(ACEGI_SECURITY_TARGET_URL_KEY);

    if (alwaysUseDefaultTargetUrl == true) {
        targetUrl = null;
    }

    if (targetUrl == null) {
        targetUrl = request.getContextPath() + defaultTargetUrl;
    }

    // user call back hook
    onSuccessfulAuthentication(request, response, authResult);
    //...
    response.sendRedirect(response.encodeRedirectURL(targetUrl));
}

The Acegi framework's AbstractProcessingFilter provides a callback method onSuccessfulAuthentication for calling user logic after a successful login - generally used for building user login context specific to application. The landing page is *pre-determined* before this call so NO matter what happens in this method, it is redirected to land on the said page. So,  if there is a data or application error while doing it, it is still going to the same page redirected to. The only way to control the flow is by throwing an exception and handling it either by Acegi Exception Handlers or catching that exception in web.xml

My Request was to be able to use a different flow, and send to a different page. In my case, If there was a user that was in our Transaction DB but not in legacy DB, We just come out throw the user an error splash screen. It dint matter much to me. However If you had a business scenario - go to a different controller, build a session different way and send to a different page - How do you do? Have you had this situation? How would you resolve it?