hibernate-demo/src/test/java/com/ankurm/hibernatedemo/naturalid/NaturalIdMutabilityTest.java

package com.ankurm.hibernatedemo.naturalid;

import static org.assertj.core.api.Assertions.assertThat;

import com.ankurm.hibernatedemo.HibernateDemoApplication;
import jakarta.persistence.EntityManager;
import jakarta.persistence.EntityManagerFactory;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

/**
 * What actually happens if you mutate a {@code @NaturalId} field Hibernate believes is
 * immutable (the default), versus one explicitly marked {@code mutable = true}?
 *
 * <p>Docs: docs/06-natural-ids.md, Topic 3.
 */
@SpringBootTest(classes = HibernateDemoApplication.class)
class NaturalIdMutabilityTest {

    @Autowired
    private EntityManagerFactory emf;

    @Test
    void mutatingAnImmutableNaturalId_throwsOnFlush() {
        EntityManager em = emf.createEntityManager();
        em.getTransaction().begin();
        ImmutableNaturalIdEntity e = new ImmutableNaturalIdEntity("CODE-A");
        em.persist(e);
        em.getTransaction().commit();
        Long id = e.getId();
        em.close();

        EntityManager em2 = emf.createEntityManager();
        Session session = em2.unwrap(Session.class);
        session.getTransaction().begin();
        ImmutableNaturalIdEntity managed = session.find(ImmutableNaturalIdEntity.class, id);
        managed.setCode("CODE-B"); // mutate the field Hibernate believes is immutable

        HibernateException ex = org.junit.jupiter.api.Assertions.assertThrows(
                HibernateException.class,
                () -> {
                    session.flush();
                });
        System.out.println("RESULT[naturalid-immutable-mutation]: flushing a changed IMMUTABLE natural id threw: "
                + ex.getClass().getName() + ": " + ex.getMessage());
        session.getTransaction().rollback();
        em2.close();

        assertThat(ex.getMessage()).containsIgnoringCase("immutable");
    }

    @Test
    void mutatingAMutableNaturalId_flushesFine_andUpdatesTheColumn() {
        EntityManager em = emf.createEntityManager();
        em.getTransaction().begin();
        MutableNaturalIdEntity e = new MutableNaturalIdEntity("CODE-X");
        em.persist(e);
        em.getTransaction().commit();
        Long id = e.getId();
        em.close();

        EntityManager em2 = emf.createEntityManager();
        em2.getTransaction().begin();
        MutableNaturalIdEntity managed = em2.find(MutableNaturalIdEntity.class, id);
        managed.setCode("CODE-Y");
        em2.getTransaction().commit(); // should NOT throw
        em2.close();

        EntityManager em3 = emf.createEntityManager();
        Object raw = em3.createNativeQuery(
                "select code from mutable_natural_id_entity where id = " + id).getSingleResult();
        em3.close();

        System.out.println("RESULT[naturalid-mutable-mutation]: flush succeeded, DB column now = " + raw);
        assertThat(raw).isEqualTo("CODE-Y");
    }

    @Test
    void mutatingAMutableNaturalId_staleLookupByOldValue_noLongerResolves() {
        EntityManager em = emf.createEntityManager();
        em.getTransaction().begin();
        MutableNaturalIdEntity e = new MutableNaturalIdEntity("CODE-OLD");
        em.persist(e);
        em.getTransaction().commit();
        Long id = e.getId();
        em.close();

        EntityManager em2 = emf.createEntityManager();
        em2.getTransaction().begin();
        MutableNaturalIdEntity managed = em2.find(MutableNaturalIdEntity.class, id);
        managed.setCode("CODE-NEW");
        em2.getTransaction().commit();
        em2.close();

        EntityManager em3 = emf.createEntityManager();
        Session session = em3.unwrap(Session.class);
        MutableNaturalIdEntity byOld = session.bySimpleNaturalId(MutableNaturalIdEntity.class).load("CODE-OLD");
        MutableNaturalIdEntity byNew = session.bySimpleNaturalId(MutableNaturalIdEntity.class).load("CODE-NEW");
        em3.close();

        System.out.println("RESULT[naturalid-mutable-stale-lookup]: byNaturalId(\"CODE-OLD\") = " + byOld
                + ", byNaturalId(\"CODE-NEW\") = " + (byNew == null ? "null" : byNew.getId()));

        assertThat(byOld).isNull();
        assertThat(byNew).isNotNull();
        assertThat(byNew.getId()).isEqualTo(id);
    }
}