问JavaEE @PreDestroy与HttpSessionListener#sessionDestroyed之间的主要区别是什么，以及何时使用what？

EN

@WebListener
public class MyHttpSessionListener implements HttpSessionListener {

    Logger logger = new Logger();

    @Override
    public void sessionCreated(HttpSessionEvent arg0) {
        // Nothing to DO
    }

    @Override
    public void sessionDestroyed(HttpSessionEvent arg0) {
        try {
            HttpSession session = arg0.getSession();
            Object sessionMyObj = session.getAttribute("myDTBManagedBean");

            if (sessionMyObj != null && sessionMyObj instanceof MyDTBManagedBean) {
                MyDTBManagedBean myDTB = (MyDTBManagedBean ) sessionMyObj;

                if (myDTB != null) {
                   //Do my unlocking logic
                }
            }
        }
    } catch (Exception e) {
        logger.error(//log exception);
    }
}