I recently stumbled upon Hibernate StatelessSession Upsert through the UPSERT discussion on JPA which talks about doing upsert operations like

doInStatelessHibernate(session -> {
    session.upsert(
        new Book()
            .setId(1L)
            .setTitle("High-Performance Hibernate")
            .setIsbn("978-9730228236")
    );
});

There’s an question with using StatelessSession with Spring Data which I think would have the starting point of an upsert implementation, but I’d rather use the repository operations if possible.