Hibernate: flush() sends SQL, commit() ends the transaction

Flushing writes pending statements so a later query sees them; it does not make them permanent.

Code

@Transactional
void demo() {
    em.persist(new Order("A-1"));
    // not in the DB yet
    em.flush();          // INSERT is sent
    // still inside the transaction - a rollback would undo it
    throw new IllegalStateException("boom");
}

Output

Hibernate: insert into orders ...
Then: rollback - the row never existed as far as anyone else is concerned.

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Published 2026-08-11