private ConfigOverlay applyRequestHandler(CommandOperation op, ConfigOverlay overlay) {
      String name = op.getStr(NAME);
      op.getStr(CLASS_NAME);
      op.getMap(PluginInfo.DEFAULTS, null);
      op.getMap(PluginInfo.INVARIANTS, null);
      op.getMap(PluginInfo.APPENDS, null);
      if (op.hasError()) return overlay;

      if (CREATE_REQHANDLER.equals(op.name)) {
        if (overlay.getReqHandlers().containsKey(name)) {
          op.addError(
              MessageFormat.format(
                  " ''{0}'' already exists . Do an ''{1}'' , if you want to change it ",
                  name, UPDATE_REQHANDLER));
          return overlay;
        } else {
          return overlay.addReqHandler(op.getDataMap());
        }
      } else if (UPDATE_REQHANDLER.equals(op.name)) {
        if (!overlay.getReqHandlers().containsKey(name)) {
          op.addError(
              MessageFormat.format(
                  " ''{0}'' does not exist . Do an ''{1}'' , if you want to create it ",
                  name, CREATE_REQHANDLER));
          return overlay;
        } else {
          return overlay.addReqHandler(op.getDataMap());
        }
      }

      return overlay;
    }