public Class<?> getClass(final String key, final Class<?> defaultClass) {
    if (containsKey(key)) {
      return getClass(key);
    } else {
      return defaultClass;
    }
  }
Gets the class from the Props. If it doesn't exist, it will return the defaultClass
dss-appconn/appconns/dss-eventchecker-appconn/src/main/java/com/webank/wedatasphere/dss/appconn/eventchecker/utils/Props.java