jetty sessionId生成

public String newSessionId(HttpServletRequest request, long created)
    {
        synchronized (this)
        {
            if (request!=null)
            {
                // A requested session ID can only be used if it is in use already.
                String requested_id=request.getRequestedSessionId();
                if (requested_id!=null)
                {
                    String cluster_id=getClusterId(requested_id);
                    if (idInUse(cluster_id))
                        return cluster_id;
                }

                // Else reuse any new session ID already defined for this request.
                String new_id=(String)request.getAttribute(__NEW_SESSION_ID);
                if (new_id!=null&&idInUse(new_id))
                    return new_id;
            }
            
            // pick a new unique ID!
            String id=null;
            while (id==null||id.length()==0||idInUse(id))
            {
                long r0=_weakRandom
                ?(hashCode()^Runtime.getRuntime().freeMemory()^_random.nextInt()^(((long)request.hashCode())<<32))
                :_random.nextLong();
                if (r0<0)
                    r0=-r0;
                long r1=_weakRandom
                ?(hashCode()^Runtime.getRuntime().freeMemory()^_random.nextInt()^(((long)request.hashCode())<<32))
                :_random.nextLong();
                if (r1<0)
                    r1=-r1;
                id=Long.toString(r0,36)+Long.toString(r1,36);
                
                //add in the id of the node to ensure unique id across cluster
                //NOTE this is different to the node suffix which denotes which node the request was received on
                if (_workerName!=null)
                    id=_workerName + id;
            }

            request.setAttribute(__NEW_SESSION_ID,id);
            return id;
        }
    }