apollo-biz/src/main/java/com/ctrip/framework/apollo/biz/service/ItemService.java/ItemService/checkItemKeyLength
class ItemService:  private boolean checkItemKeyLength(String key) {
    if (!StringUtils.isEmpty(key) && key.length() > bizConfig.itemKeyLengthLimit()) {
      throw new BadRequestException("key too long. length limit:" + bizConfig.itemKeyLengthLimit());
    }
    return true;
  }