code: public Object getUserModelAfterLogin(HttpServletRequest request) {
  		Object model = userPrincipal.getUserFromSession(request);
  		if (model == null)
  			model = userPrincipal.getUserFromPrincipal(request);
  		return (Model) model;
  	}
docs: 获得登陆后的User相关信息
  本方法必须在上面login执行后，或者用户通过j_security_check登陆后才可有效
  首先从HttpSession中查询，HttpSession中资料是由getUserFromPrincipal
  第一次执行生成的。
  
  @param request
  @return　UserModel