how should migrate my DBRef fields with mongock?

I have a problem with migrating an entity which has DBRef fields. If I change any field in this entity, my DBRefs are gone. What should I do?

    Query query = new Query();

    List<Criteria> criteriaList = new ArrayList<Criteria>();

    criteriaList.add(Criteria.where("created").exists(false));
    criteriaList.add(Criteria.where("updated").exists(false));

    query.addCriteria(new Criteria().orOperator(criteriaList.toArray(new Criteria[criteriaList.size()])));

    List<Asset> results = mongoTemplate.find(query, Asset.class);
    results.forEach(asset -> {
        asset.setCreated(asset.getCreatedBy().getCreated());

        mongoTemplate.save(asset);
    });

in summary, its problem is the MongoTemplate. mongoTemplate.save(...) creates a new entity and saves it to DB. As a consequence, if you want to change/update a field in your entity, you should use mongoTemplate.updateFirst(...). My solution is as the following.

public void createAssetCreateOrUpdateDateIfNot(MongockTemplate mongockTemplate) {
    MongoTemplate mongoTemplate = mongockTemplate.getImpl();

    Query queryGetAssetsCreatedOrUpdatedIsNot = new Query();

    List<Criteria> criteriaList = new ArrayList<Criteria>();
    criteriaList.add(Criteria.where("created").exists(false));
    criteriaList.add(Criteria.where("updated").exists(false));

    queryGetAssetsCreatedOrUpdatedIsNot
            .addCriteria(new Criteria().orOperator(criteriaList.toArray(new Criteria[criteriaList.size()])));

    List<Asset> results = mongoTemplate.find(queryGetAssetsCreatedOrUpdatedIsNot, Asset.class);

    if (results.size() > 0) {
        for (Asset asset : results) {
            Date createdDate = (asset.getCreatedBy().getCreated() != null)
                    ? asset.getCreatedBy().getCreated()
                    : new Date();
            Date updateDate = (asset.getModifiedBy().getCreated() != null)
                    ? asset.getModifiedBy().getCreated()
                    : new Date();

            Query queryGetAssetViaId = new Query();
            queryGetAssetViaId.addCriteria(Criteria.where("id").is(asset.getId()));

            Update update = new Update()
                    .set("created", createdDate)
                    .set("updated", updateDate);

            mongoTemplate.updateFirst(queryGetAssetViaId, update, Asset.class);
        }
    }
}