code: protected ItemData getPersistedItemData(String identifier) throws RepositoryException
     {
        ItemData data = super.getItemData(identifier);
  
        // set ACL
  
        if (data != null && data.isNode())
        {
           data = initACL(null, (NodeData)data);
        }
  
        if (cache.isEnabled())
        {
           if (data != null)
           {
              cache.put(data);
           }
           else if (identifier != null)
           {
              // no matter does property or node expected - store NullNodeData
              cache.put(new NullNodeData(identifier));
           }
        }
        return data;
     }
docs: Call
  {@link org.exoplatform.services.jcr.impl.dataflow.persistent.WorkspacePersistentDataManager#getItemData(java.lang.String)
  WorkspaceDataManager.getItemDataByIdentifier(java.lang.String)} and cache result if non null returned.
  
  @see org.exoplatform.services.jcr.impl.dataflow.persistent.WorkspacePersistentDataManager#getItemData(java.lang.String)