public class LoginSupport extends ActionSupport {
    public void prepare() {
        final HttpServletRequest request = ServletActionContext.getRequest();
        request.getSession().invalidate();

        // generate new session (and id)
        final HttpSession newSession = request.getSession();
    }
}

java.lang.IllegalStateException: getAttribute: Session already invalidated
    at org.apache.catalina.session.StandardSession.getAttribute(StandardSession.java:1011)
    at org.apache.catalina.session.StandardSessionFacade.getAttribute(StandardSessionFacade.java:109)
    at org.apache.struts2.dispatcher.SessionMap.get(SessionMap.java:161)