To save an object in Hibernate, you need to:
1️⃣ Open a Hibernate Session.
2️⃣ Start a transaction.
3️⃣ Call session.save() or session.persist() to make the object persistent.
4️⃣ Commit the transaction to write the object to the database.
5️⃣ Close the session to release resources.
🔹 Example step-by-step:
Session session = sessionFactory.openSession(); // 1️⃣ Open session
Transaction tx = session.beginTransaction(); // 2️⃣ Start transaction
User user = new User(); // Create new entity
user.setUsername("alice");
user.setEmail("alice@example.com");
session.save(user); // 3️⃣ Save object → schedules INSERT
tx.commit(); // 4️⃣ Commit transaction → executes SQL
session.close(); // 5️⃣ Close session
🔹 What happens under the hood:
✅ session.save(user) → assigns an ID and marks the object as persistent, adding it to the first-level cache.
✅ Hibernate queues the SQL INSERT statement in memory.
✅ tx.commit() → triggers a flush → executes the actual SQL insert on the database.
✅ After commit, the object’s generated ID is available, and the session’s changes are persisted.
🔹 Important notes:
- Always save objects inside a transaction → without
commit(), data won’t persist to the database. - Remember to close the session to avoid connection and memory leaks.
🔹 Using JPA-standard persist() instead of save():
session.persist(user); // also makes the entity persistent, but returns void
✅ Key takeaway:
To save an object in Hibernate: open a session, start a transaction, call save() or persist(), commit the transaction, and close the session.