private User validate(String serviceUrl, String serviceTicket) throws AuthenticationException
{
User user = null;
URL url = new URL(agent.getParamString(AGENT_PARAM_CASSERVICE));
url.addFolderOrFile(SERVICE_VALIDATE_URL_PART);
String toUrl = url.toString();
PostMethod method = new PostMethod(toUrl);
method.setParameter(URL_PARAM_SERVICE, serviceUrl);