What methods can be used to transition an entity from one state to another in Hibernate?

In Hibernate, entities can be in different states: transient (new, not associated with a session), persistent (associated with a session), detached (disconnected from a session).

Transitioning an entity from one state to another is done using the following methods:

• save() — saves a new (transient) entity to the database, transitioning it to persistent.
• persist() — similar to save(), but with some differences in transaction behavior and identifier generation.
• update() — transitions a detached entity back to persistent, associating it with the current session.
• merge() — copies the state of a detached entity into a managed entity, returning the managed instance.
• saveOrUpdate() — saves a new entity or updates a detached one.
• delete() — removes a persistent entity from the database.

Example:

Session session = sessionFactory.openSession();
Transaction tx = session.beginTransaction();

// transient
Entity e = new Entity();

// transition to persistent
session.save(e);

// detach
session.evict(e);

// update (attach)
session.update(e);

// merge
Entity managed = (Entity) session.merge(e);

tx.commit();
session.close();

Thus, the save/persist, update, merge methods allow transitioning entities between states in Hibernate.