code: private ViewNode getRootViewNode(HttpServletRequest request) throws Exception {
      String rooNodeID = getRootNodeID(request);
      if (rooNodeID == null){
        Debug.logError("[JdonFramework] root Id is null ! " , module);
        return null;
      }
      Debug.logVerbose("[JdonFramework] get the tree's root Node: " + rooNodeID, module);
      ViewNode rNode = new ViewNode(rooNodeID, rooNodeID, true);
      rNode.setRoot(true);
      return rNode;
    }
docs: 根据后台Root得到显示的根节点
  @param request HttpServletRequest
  @throws Exception
  @return ViewNode