Explanation/Reference:
Entity Listeners and Callback Methods
A method may be designated as a lifecycle callback method to receive notification of entity lifecycle events.
A lifecycle callback method can be defined on an entity class, a mapped superclass, or an entity listener class associated with an entity or mapped superclass.
Reference: How to inject a spring's service bean into a JPA Entity?
http://stackoverflow.com/questions/3747268/how-to-inject-a-springs-service-bean-into-a-jpa-entity