@VisibleForTesting
  public static void addSummaryHandler(String tableType, String handlerName) throws ClassNotFoundException {
    if (tableType == null || handlerName == null) {
      throw new IllegalArgumentException("The input parameters shouldn't be null");
    }
    // Make sure the handler is in classpath
    Class.forName(handlerName);
    NON_NATIVE_SUMMARY_HANDLER.put(tableType, handlerName);
  }
Helper method of exportInJson.

@param jsonOutput A string, JSON formatted string about metadataSummary.
@param filename   Path of a file in String where the summary needs to be output to.
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/tools/metatool/MetaToolTaskMetadataSummary.java