code: public static Dn concatDn(String rdnAttribute, String rdnValue, Dn basedn) {
          try {
              Rdn rdn = new Rdn(rdnAttribute, rdnValue);
              return basedn.add(rdn);
          } catch (LdapInvalidDnException e) {
              throw new LdapRuntimeException(e);
          }
      }
docs: Returns a {@link Dn} consisting of baseDn extended by an Rdn of type rdnAttribute and value rdnValue.