code: public String getValidatorId(FaceletContext ctx) {
          if (validatorId == null) {
              TagAttribute idAttr = getAttribute("validatorId");
              if (idAttr == null) {
                  return null;
              } else {
                  return idAttr.getValue(ctx);
              }
          }
          return validatorId;
      }
docs: <p>Retrieve the id of the validator that is to be created and
  added to the parent <code>EditableValueHolder</code>.  All
  subclasses should override this method because it is important
  for Facelets to have a unique way of identifying the validators
  that are added to this <code>EditableValueHolder</code> and
  allows exclusions to work properly. An exclusion is a validator
  declaration that has the attribute "disabled" which resolves to
  false, instructing Facelets not to register a default validator
  with the same id.</p>