I am reading Head First JSP and Servlets and preparing for the exam. It says in topic of HttpSessionBindingListener, that its valueBound() and valueUnBound() can be used when we need to synchronize with the database. I am not aware much about entities with respect to databases. But that is what i get that let say we can make Dog class an Entity and make it implement HttpSessionBindingListener. But still i am unable to understand when we say when it is added to session and it is removed, how valueBound() and valueUnBound() can help synchonize with the database. Are these methods where we will be doing database CRUD operations?