code: protected ItemData getPersistedItemData(NodeData parentData, QPathEntry name, ItemType itemType)
        throws RepositoryException
     {
        ItemData data = super.getItemData(parentData, name, itemType);
        if (cache.isEnabled())
        {
           if (data == null)
           {
              if (itemType == ItemType.NODE || itemType == ItemType.UNKNOWN)
              {
                 cache.put(new NullNodeData(parentData, name));
              }
              else
              {
                 cache.put(new NullPropertyData(parentData, name));
              }
           }
           else
           {
              cache.put(data);
           }
        }
        return data;
     }
docs: Get persisted ItemData.
  
  @param parentData
  parent
  @param name
  Item name
  @param itemType
  item type
  @return ItemData
  @throws RepositoryException
  error