if (_scavenger == null) { _scavenger = new SessionScavenger(); _scavenger.start(); }
_sessionHandler.getServer().getThreadPool().dispatch(new SessionScavenger());
    public void doStart()    throws Exception    {        _context=ContextHandler.getCurrentContext();        _loader = Thread.currentThread().getContextClassLoader();                if (_sessions==null)            _sessions=new HashMap();        if (_sessionIdManager==null)        {            Server server = getSessionHandler().getServer();            synchronized (server)            {                _sessionIdManager=server.getSessionIdManager();                if (_sessionIdManager==null)                {                    _sessionIdManager=new HashSessionIdManager();                    server.setSessionIdManager(_sessionIdManager);                }            }        }        if (!_sessionIdManager.isStarted())            _sessionIdManager.start();                super.doStart();        // Start the session scavenger if we haven't already        if (_scavenger == null)        {            _scavenger = new SessionScavenger();            _scavenger.start();        }    }