Perform this action. Invalidate the session and create a new
UserBean to replace the old one.
// invalidate the current session
req.getSession().invalidate();
// create a new one, and add a new UserBean to it
HttpSession session = req.getSession();
UserBean ub = UserBeanFactory.newInstance();
session.setAttribute(LoginAction.USERBEAN_ATTR, ub);
return true;