Save and Persist in Hibernate

In Hibernate, both the "save()" and "persist()" methods are used to save an entity object into the database, but there are some differences between them.

1. Session Context

   - "save()" method is defined in the "Session" interface, which means it is available within the session context.

   - "persist()" method is defined in the "EntityManager" interface (for JPA), and it is commonly used in JPA implementations like Hibernate. It's available within the persistence context.

2. Return Value

   - "save()" method returns the identifier (primary key) of the saved entity immediately after saving it into the database.

   - "persist()" method does not return anything; it only makes the entity managed and persistent.

3. State Transition

   - "save()" method transitions the entity from the transient state (i.e., not associated with any session) to the persistent state (i.e., associated with the session and mapped to a corresponding database record).

   - "persist()" method also transitions the entity from the transient state to the persistent state, but it's typically used for newly created entities. It throws an exception if the entity is already managed.

4. Hibernate-Specific

   - "save()" method is specific to Hibernate and is not part of the JPA specification.

   - "persist()" method is part of the JPA specification and is implemented by all JPA providers, including Hibernate.

5. Generated Identifier

   - When using "save()" method, Hibernate generates the identifier value immediately, so you can access it after calling the "save()" method.

   - When using "persist()" method, the identifier value might not be generated immediately. It may be generated at flush time or when the transaction is committed, so you can't access it right away.

6. Transitive Persistence

   - "save()" method does not cascade the save operation to associated entities. You need to explicitly call "save()" for associated entities if you want to save them.

   - "persist()" method cascades the persist operation to associated entities, so if an entity has relationships with other entities and those relationships are marked for cascade persist, they will also be persisted automatically.

In summary, both "save()" and "persist()" methods are used to persist entity objects, but "persist()" is more aligned with the JPA specification and provides better support for transitive persistence. However, "save()" method is specific to Hibernate and provides immediate access to the generated identifier.