Enterprise JavaBeans, Third Edition

Overview for EJB 1.1 Readers

The following overview of EJB 1.1 container-managed persistence is pretty much duplicated in Chapter 6, but for EJB 1.1 readers who have not read Chapter 6, the overview is important to understanding the context of entity beans and container-managed persistence.

In Chapter 4, we started developing some simple enterprise beans, skipping over a lot of the details about developing enterprise beans. In this chapter, we’ll take a thorough look at the process of developing entity beans.

Entity beans model business concepts that can be expressed as nouns. This is a rule of thumb rather than a requirement, but it helps in determining when a business concept is a candidate for implementation as an entity bean. In grammar school you learned that nouns are words that describe a person, place, or thing. The concepts of person and place are fairly obvious: a person EJB might represent a customer or passenger, and a place EJB might represent a city or port-of-call. Similarly, entity beans often represent things: real-world objects like ships, customers, and so on. An entity bean can even represent a fairly abstract thing, such as a reservation. Entity beans describe both the state and behavior of real-world objects and allow developers to encapsulate the data and business rules associated with specific concepts; a Ship EJB encapsulates the data and business rules associated with a ship, and so on. This makes it possible for data associated with a concept to be manipulated ...