Building Java Enterprise Applications

Coding the Bean

It’s finally time to write some code. If you are new to EJB, you should pick up the aforementioned Enterprise JavaBeans and skim through Chapter 4 before continuing on. That should give you enough of a basic foundation to understand this chapter, as I’m going to move through the basic entity bean code pretty quickly.

I’ll start the entity bean work with the office data structure. Remember the OFFICES table from last chapter? The table structure is shown again in Figure 4-1 for reference.

Figure 4-1. The office data structure

I’ll use this structure for the first entity bean, as it has a very simple structure. It also does not depend on any other objects (i.e., it has no foreign keys), a subject I will address in the next chapter. Dependent objects introduce some additional considerations, but I will look at those when we start to code beans for tables with foreign keys, like the USERS table. For the time being, it’s enough to know that this office structure is as simple as it gets. You need to store the ID (an int), the city (a String), and the state (another String).

As this bean is simple in nature, it is a perfect candidate for container-managed persistence (CMP). There are no special JDBC calls that need to be made, no multiple-table queries, and no explicit data caching that needs to be performed. In the absence of these special cases, CMP is almost always a ...