JPA: Override Auto generated ID

I wrote my own generator to solve the issue.

public class UseExistingIdOtherwiseGenerateUsingIdentity extends IdentityGenerator {

    @Override
    public Serializable generate(SharedSessionContractImplementor session, Object object) throws HibernateException {
        Serializable id = session.getEntityPersister(null, object).getClassMetadata().getIdentifier(object, session);
        return id != null ? id : super.generate(session, object);
    }
}

and use it like this: (replace the package name)

@Id
@GenericGenerator(name = "UseExistingIdOtherwiseGenerateUsingIdentity", strategy = "{package}.UseExistingIdOtherwiseGenerateUsingIdentity")
@GeneratedValue(generator = "UseExistingIdOtherwiseGenerateUsingIdentity")
@Column(unique = true, nullable = false)
protected Integer id;

You cannot override it. First of all JPA do not provide way to do it. Second problem is that GenerationType.AUTO can produce such a column type that will not accept user assigned value via SQL statement.

Perform import of data manually and do not try to use application itself as an import tool.