Hibernate Lifecycle

in Hibernate, each entity is associated with the lifecycle. The entity object passes through the different stages of the lifecycle:

Transient state

The transient state is the initial state of an object.
Once we create an instance of POJO class, then the object entered in the transient state.
Here, an object is not associated with the Session. So, the transient state is not related to any database.
Hence, modifications in the data don’t affect any changes in the database.
The transient objects exist in the heap memory. They are independent of Hibernate.

Employee e=new Employee(); //Here, object enters in the transient state.  
e.setId(101);  
e.setFirstName("Gaurav");  
e.setLastName("Chawla");

As soon as the object associated with the Session, it entered in the persistent state.
Hence, we can say that an object is in the persistence state when we save or persist it.
Here, each object represents the row of the database table.
So, modifications in the data make changes in the database.

We can use any of the following methods for the persistent state.

session.save(e);  
session.persist(e);  
session.update(e);  
session.saveOrUpdate(e);  
session.lock(e);  
session.merge(e);

Once we either close the session or clear its cache, then the object entered into the detached state.
As an object is no more associated with the Session, modifications in the data don’t affect any changes in the database.
However, the detached object still has a representation in the database.
If we want to persist the changes made to a detached object, it is required to reattach the application to a valid Hibernate session.
To associate the detached object with the new hibernate session, use any of these methods - load(), merge(), refresh(), update() or save() on a new session with the reference of the detached object.