apollo-client/src/main/java/com/ctrip/framework/apollo/internals/AbstractConfig.java/AbstractConfig/getEnumProperty
class AbstractConfig:  @Override
  public <T extends Enum<T>> T getEnumProperty(String key, Class<T> enumType, T defaultValue) {
    try {
      String value = getProperty(key, null);

      if (value != null) {
        return Enum.valueOf(enumType, value);
      }
    } catch (Throwable ex) {
      Tracer.logError(new ApolloConfigException(
          String.format("getEnumProperty for %s failed, return default value %s", key,
              defaultValue), ex));
    }

    return defaultValue;
  }