[FIXED] Hibernate - Insert generated id in column other than id one on save

Issue

is there a way to perform insertion of an @Id-column value into a non @Id column when entity is being created/updated to avoid double-save-ing?

@Entity
class DummyEntity {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO, generator = "dummy_id_generator")
    @SequenceGenerator(name = "dummy_id_generator", sequenceName = "dummy_id_seq")
    Long id;

    Long rootId;
}

@Repository
class DummyEntityRepo implements JpaRepository<DummyEntity, Long> {}

@Service
class DummyEntityService {
    @Autowired
    DummyEntityRepo repo;

    void save(DummyEntityVO newDummyEntity) {
        var newEntity = newDummyEntity.mapToEntity();

        // !!! double save here !!!
        repo.save(newEntity);
        if(newEntity.getRootId() == null) {
            newEntity.setRootId(newEntity.getId());
            repo.save(newEntity);
        }
    }
}

What I was thinking was, since @Id is based on a sequence, I can try extracting next value from it and setting it as id and rootId before saving

Long nextId = // get next id somehow
newEntity.setId(newId);
if (newEntity.getRootId()) {
    newEntity.setRootId(nextId);
}
repo.save(newEntity);

However:

• I don't like perspective of interfering with Hibernate's id acquisition & saving methods
• I found package org.springframework.jdbc.support.incrementer but unfortunately there is no sequence based OOB incrementer for my DB so it would require a custom implementation (found something promising here though)

Solution

@GeneratorType allows to generate/set values into entity during insertion phase. Suppose your entity looks like this:

@Entity
class DummyEntity {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO, generator = "dummy_id_generator")
    @SequenceGenerator(name = "dummy_id_generator", sequenceName = "dummy_id_seq")
    Long id;

    @GeneratorType(type = RecordIdGenerator.class, when = GenerationTime.INSERT)
    Long rootId;
}

And your RecordIdGenerator class looks like:

public class RecordIdGenerator implements ValueGenerator<Long> {
    @Override
    public Long generateValue(Session session, Object owner) {
        return ((DummyEntity)owner).getId();
    }
}

Then when you'll insert new record hibernate will generate similar queries:

Hibernate: select nextval ('dummy_id_seq')
Hibernate: insert into dummy (record_id, id) values (?, ?)

and record_id will be equal to id

Answered By - eparvan