public List<String> getStringList(final String key, final List<String> defaultValue) {
    if (containsKey(key)) {
      return getStringList(key);
    } else {
      return defaultValue;
    }
  }
Returns a list of strings with the comma as the separator of the value. If the value is null,
it'll return the defaultValue.
dss-appconn/appconns/dss-eventchecker-appconn/src/main/java/com/webank/wedatasphere/dss/appconn/eventchecker/utils/Props.java