What are entity states in Hibernate 7 and how do they transition?

Every entity instance in Hibernate exists in one of three states relative to a Session. Hibernate 7 enforces stricter rules on detached entities.

// TRANSIENT
Product p = new Product("Laptop", new BigDecimal("999"));

// TRANSIENT -> PERSISTENT
session.persist(p);  // INSERT scheduled

// Auto dirty checking: change field -> UPDATE at flush
p.setPrice(new BigDecimal("899"));
session.getTransaction().commit();  // flush: UPDATE sent

// PERSISTENT -> DETACHED (session closes)
// p is detached: changes NOT tracked

// Hibernate 7: ONLY merge() re-integrates detached entities
Product managed = session2.merge(p);  // copies detached state
managed.setPrice(new BigDecimal("799"));

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