How does Hibernate detect dirty state of an entity object?

Question

Is it using some kind of byte codes modification to the original classes?

Or, maybe Hibernate get the dirty state by compare the given object with previously persiste

Answer 1

It is simple-- when you load/get entity object by id and then set its new field values by setter method and close session without calling update() method. then hibernate automatically update the changed value in the table without affecting other fields. and at the same time entity object is in dirty state.