Add Hibernate 7 batches 2-6, batch 7, and batch 8: mapping styles, JPA annotations, natural IDs, @Immutable, stored procedures, in-memory test databases, JNDI mocking, proxies, associations, temporal mapping, named queries, HQL, Criteria API, EntityManager bootstrapping, Ehcache 3 L2 cache configuration, HikariCP connection pooling, Hibernate Validator CDI integration, aggregate functions, sorting, pagination, interceptors, and Hibernate Search 8 (Hibernate 7.4.5.Final + Spring Boot 4.1.1 + JDK 25)
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package com.ankurm.hibernatedemo.scenario;
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import com.ankurm.hibernatedemo.model.Book;
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import jakarta.persistence.EntityManager;
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import jakarta.persistence.EntityManagerFactory;
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import org.hibernate.Session;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import org.springframework.boot.CommandLineRunner;
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import org.springframework.context.annotation.Profile;
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import org.springframework.stereotype.Component;
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/**
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* Backs ankurm.com post 4859 ("Hibernate 7: get() vs load()") and
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* docs/01-get-vs-load.md. Captured verbatim into docs/output/get-vs-load.txt by
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* {@code scripts/run.sh getvsload}.
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*
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* <p>Each step opens its own {@link EntityManager} deliberately, so the SQL log lines that
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* bracket a step are unambiguously that step's own traffic — there is no shared session
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* whose first-level cache could quietly answer a later {@code get()} for free.
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*/
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@Component
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@Profile("getvsload")
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public class GetVsLoadRunner implements CommandLineRunner {
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private static final Logger DEMO = LoggerFactory.getLogger("DEMO");
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private final EntityManagerFactory emf;
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public GetVsLoadRunner(EntityManagerFactory emf) {
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this.emf = emf;
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}
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@Override
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public void run(String... args) {
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Long existingId = seedOneBook();
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long missingId = existingId + 999_000L;
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step1_getExisting(existingId);
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step2_getMissing(missingId);
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step3_getReferenceExisting_noSelectUntilAccessed(existingId);
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step4_getReferenceMissing_exceptionOnlyOnAccess(missingId);
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step5_getReferenceThenSessionClosed_lazyInitException(existingId);
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step6_proxyVsRealIdentity(existingId);
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}
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private Long seedOneBook() {
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EntityManager em = emf.createEntityManager();
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em.getTransaction().begin();
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Book book = new Book("Effective Java", "Joshua Bloch");
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em.persist(book);
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em.getTransaction().commit();
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Long id = book.getId();
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em.close();
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DEMO.info("SEED: inserted Book id={}", id);
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return id;
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}
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private void step1_getExisting(Long id) {
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DEMO.info("--- Step 1: session.get() on an existing id ---");
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EntityManager em = emf.createEntityManager();
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em.getTransaction().begin();
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Session session = em.unwrap(Session.class);
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DEMO.info("about to call session.get(Book.class, {})", id);
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Book book = session.get(Book.class, id);
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DEMO.info("get() returned: {}", book);
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em.getTransaction().commit();
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em.close();
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}
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private void step2_getMissing(long missingId) {
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DEMO.info("--- Step 2: session.get() on a missing id ---");
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EntityManager em = emf.createEntityManager();
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em.getTransaction().begin();
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Session session = em.unwrap(Session.class);
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DEMO.info("about to call session.get(Book.class, {})", missingId);
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Book book = session.get(Book.class, missingId);
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DEMO.info("get() returned: {} (no exception thrown)", book);
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em.getTransaction().commit();
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em.close();
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}
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private void step3_getReferenceExisting_noSelectUntilAccessed(Long id) {
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DEMO.info("--- Step 3: session.getReference() on an existing id ---");
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EntityManager em = emf.createEntityManager();
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em.getTransaction().begin();
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Session session = em.unwrap(Session.class);
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Book proxy = session.getReference(Book.class, id);
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DEMO.info("getReference() returned proxy of class {} -- no SELECT above this line", proxy.getClass().getName());
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DEMO.info("now calling proxy.getTitle() ...");
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String title = proxy.getTitle();
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DEMO.info("getTitle() returned '{}' -- the SELECT for this ran just above this line", title);
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em.getTransaction().commit();
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em.close();
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}
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private void step4_getReferenceMissing_exceptionOnlyOnAccess(long missingId) {
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DEMO.info("--- Step 4: session.getReference() on a missing id ---");
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EntityManager em = emf.createEntityManager();
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em.getTransaction().begin();
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Session session = em.unwrap(Session.class);
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Book proxy = session.getReference(Book.class, missingId);
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DEMO.info("getReference() returned a proxy for a row that does not exist -- no exception yet: {}", proxy.getClass().getName());
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try {
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proxy.getTitle();
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DEMO.info("no exception -- this line should be unreachable");
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} catch (RuntimeException e) {
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DEMO.info("accessing the proxy threw {}: {}", e.getClass().getName(), e.getMessage());
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}
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em.getTransaction().rollback();
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em.close();
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}
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private void step5_getReferenceThenSessionClosed_lazyInitException(Long id) {
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DEMO.info("--- Step 5: proxy accessed after its session is closed ---");
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EntityManager em = emf.createEntityManager();
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em.getTransaction().begin();
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Session session = em.unwrap(Session.class);
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Book proxy = session.getReference(Book.class, id);
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em.getTransaction().commit();
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em.close();
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DEMO.info("session closed. proxy in hand: {}", proxy.getClass().getName());
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try {
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proxy.getTitle();
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DEMO.info("no exception -- this line should be unreachable");
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} catch (RuntimeException e) {
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DEMO.info("accessing the proxy after close threw {}: {}", e.getClass().getName(), e.getMessage());
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}
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}
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private void step6_proxyVsRealIdentity(Long id) {
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DEMO.info("--- Step 6: proxy identity vs a real loaded instance ---");
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EntityManager em = emf.createEntityManager();
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em.getTransaction().begin();
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Session session = em.unwrap(Session.class);
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Book real = session.get(Book.class, id);
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// second em/session so this is a genuinely separate proxy, not the same cached instance
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EntityManager em2 = emf.createEntityManager();
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em2.getTransaction().begin();
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Session session2 = em2.unwrap(Session.class);
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Book proxy = session2.getReference(Book.class, id);
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DEMO.info("real.getClass() = {}", real.getClass().getName());
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DEMO.info("proxy.getClass() = {}", proxy.getClass().getName());
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DEMO.info("proxy instanceof Book.class: {}", Book.class.isInstance(proxy));
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DEMO.info("real.getClass() == proxy.getClass(): {}", real.getClass() == proxy.getClass());
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DEMO.info("real.equals(proxy) before proxy access: {}", real.equals(proxy));
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em.getTransaction().commit();
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em.close();
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em2.getTransaction().commit();
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em2.close();
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}
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}
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