Head First EJB

Chapter 6. Bean/Entity Synchronization: Being an Entity Bean

Entity beans are actors. As long as they’re alive, they’re either in the pool or they’re being somebody. Somebody from the underlying persistent store. In other words, an entity from the database. When a bean is playing a part, the bean and the underlying entity have to stay in sync. Imagine the horror if the bean is pretending to be, say, Audrey Leone, and someone lowers Audrey’s credit limit in the database... but forgets to tell the bean. The bean, acting as Audrey, is happily authorizing purchases for more than Audrey’s current limit. Or what if a client uses the bean to modify Audrey’s address, but the bean hangs on to the new info without telling the database... yikes!

Objectives

Entity Bean Lifecycle

Official:		What it really means:
6.1	Identify correct and incorrect statements or examples about the Bean Provider’s view and programming contract for CMP, including the requirements for a CMP entity bean.	This objective can hit you on almost anything related to entity beans, so you pretty much have to know it all, including the details of a CMP entity bean lifecycle, the container callback methods of javax.ejbEntityBean, what you must write in a bean class, and what a bean can get from its EJBContext. You have to know that passivation in entity beans is different from session bean passivation, because entity beans go back to ...