BaseService.update returns object that is not a hibernate proxy

[simonseyock]

The BaseService.update method serializes the given entity, deserializes it again and saves it. This causes the resulting object to not be a proper hibernate proxy. (edit: to be more precise: any related objects are no hibernate proxies anymore, but merely the objects that got deserialized. It can be that the object only contains an Id if the field was using the BaseEntityIdSerializer). Also all other managed instances of the object are broken as well.

Firstly the question arises why this code with the serialization and deserialization exists:

    @PreAuthorize("hasRole('ROLE_ADMIN') or hasPermission(#entity, 'UPDATE')")
    @Transactional(isolation = Isolation.SERIALIZABLE)
    public S update(Long id, S entity) throws IOException {
        Optional<S> persistedEntityOpt = repository.findById(id);

        ObjectNode jsonObject = objectMapper.valueToTree(entity);

        // Ensure the created timestamp will not be overridden.
        S persistedEntity = persistedEntityOpt.orElseThrow();
        OffsetDateTime createdTimestamp = persistedEntity.getCreated();
        String serialized = createdTimestamp != null ? createdTimestamp.toInstant().toString() : null;
        jsonObject.put("created", serialized);

        S updatedEntity = objectMapper.readerForUpdating(persistedEntity).readValue(jsonObject);

        return repository.save(updatedEntity);
    }

I suppose this in place to leave the entity intact. Is this really neccessary?

The simplest way to achieve the same would be:

  entity.setCreated(persistedEntity.getCreated());

Another way to solve this would be to use the lombok @SuperBuilder annotation and create a copy. See https://www.projectlombok.org/features/experimental/SuperBuilder

For our project we used the following workaround:

            var updatedEntity = super.update(entityId, entity);

            entityManager.flush(); // flush database changes
            entityManager.detach(updatedEntity); // this way the broken object is no longer a managed hibernate object
            // without the detach the findById would just return the broken managed object
            updatedEntity = repository.findById(entityId).orElseThrow(); // get a new managed hibernate proxy object

This might not be feasible for the BaseService as I assume that flush does have performance issues if called often.

[simonseyock]

It might also be interesting to mention: partialUpdate does use a similar process.

[simonseyock]

And well another option would be to not return the resulting object. But this would still cause the managed object to be broken.