@Override
  protected void doAlteration(DataConnector connector) {
    Map<String, String> newParams = desc.getConnectorProperties();
    Map<String, String> params = connector.getParameters();

    // if both old and new params are not null, merge them
    if (params != null && newParams != null) {
      params.putAll(newParams);
      connector.setParameters(params);
    } else {
      // if one of them is null, replace the old params with the new one
      connector.setParameters(newParams);
    }
  }
Operation process of altering a dataconnector's properties.
ql/src/java/org/apache/hadoop/hive/ql/ddl/dataconnector/alter/properties/AlterDataConnectorSetPropertiesOperation.java