code: private String convertBlanksToNull(String string) {
          if (string != null && string.trim().length() > 0) {
              return string;
  
          } else {
              return null;
          }
      }
docs: Metatype doesn't allow fields without a default but we want
  nulls for unspecified JNDI names so convert "" (our default)
  to null.
  
  @param string
  @return