@Override
    public SaslServer createSaslServer(String mechanism, String protocol, String serverName,
      Map<String, ?> props, CallbackHandler cbh) throws SaslException {
      return "PLAIN".equals(mechanism) ? new SaslPlainServer(cbh) : null;
    }
This class was copied from Hadoop Common (3.1.2) and subsequently modified.
hbase-examples/src/main/java/org/apache/hadoop/hbase/security/provider/example/SaslPlainServer.java