apollo-biz/src/main/java/com/ctrip/framework/apollo/biz/service/ItemService.java/ItemService/checkItemValueLength
class ItemService:  private boolean checkItemValueLength(long namespaceId, String value) {
    int limit = getItemValueLengthLimit(namespaceId);
    if (!StringUtils.isEmpty(value) && value.length() > limit) {
      throw new BadRequestException("value too long. length limit:" + limit);
    }
    return true;
  }