class SessionListener implements HttpSessionListener {

    private static final Logger logger = LoggerFactory.getLogger(SessionListener.class);

    @Override
    public void sessionCreated(HttpSessionEvent event) {
        logger.trace("Session created");
    }

    @Override
    public void sessionDestroyed(HttpSessionEvent event) {<FILL_FUNCTION_BODY>}

}

        try {
            ZooKeeper zk = (ZooKeeper) event.getSession().getAttribute("zk");
            zk.close();
            logger.trace("Session destroyed");
        } catch (InterruptedException ex) {
            logger.error(Arrays.toString(ex.getStackTrace()));
        }
    
<no_super_class>