Question

Why do we need Java Persistence API listeners when callbacks and listeners are the same in functionality?

Answer 1

Q Why do we need Java Persistence API listeners when callbacks and listeners are the same in functionality?

Well we use Java Persistence API listeners when callbacks and listeners are the same in functionality because we can define several entity Persistence API listeners per entity at respected levels of the hierarchy. We can also show or define various callbacks at every different level of the hierarchy. But we are not able to define two API listeners for the same event in the same entity or the same entity API listener.

When an event is invoked, the listeners are executed in this order:

• EntityListeners for a given entity or superclass in order

• Entity listeners for the super-classes (staring with highest order)

• Entity Listeners for the entity

• Callbacks of the super-classes (Higer will be first)

• Callbacks of the entity

We can stop the entity API listeners inheritance by using the @ExcludeSuperclassListeners, all superclasses EntityListeners will then be ignored. So its is necessary to use API listeners.