apollo-biz/src/main/java/com/ctrip/framework/apollo/biz/service/ItemService.java/ItemService/update
class ItemService:  @Transactional
  public Item update(Item item) {
    checkItemValueLength(item.getNamespaceId(), item.getValue());
    Item managedItem = itemRepository.findById(item.getId()).orElse(null);
    BeanUtils.copyEntityProperties(item, managedItem);
    managedItem = itemRepository.save(managedItem);

    auditService.audit(Item.class.getSimpleName(), managedItem.getId(), Audit.OP.UPDATE,
                       managedItem.getDataChangeLastModifiedBy());

    return managedItem;
  }