if (session != null && session.getAttribute(CONST_CAS_ASSERTION) == null && ticket != null) {
try {
final String service = constructServiceUrl(request, response);
logger.debug("Attempting CAS ticket validation with service={} and ticket={}", service, ticket);
request.login(service, ticket);
if (request.getUserPrincipal() instanceof AssertionPrincipal) {
final AssertionPrincipal principal = (AssertionPrincipal) request.getUserPrincipal();
logger.debug("Installing CAS assertion into session.");
request.getSession().setAttribute(CONST_CAS_ASSERTION, principal.getAssertion());
} else {