public void setHiveConfVariables(Map<String, String> hiveConfVariables) {
    if (hiveConfVariables == null) {
      this.hiveConfVariables.clear();
      return;
    }
    this.hiveConfVariables = hiveConfVariables;
  }
Use getNullString() to get the null string to be used.
@return true if null representation should be an empty string
beeline/src/java/org/apache/hive/beeline/BeeLineOpts.java