As you learned in Chapter 1, Enterprise JavaBeans is a component model for component transaction monitors, which are the most advanced type of business application servers available today. To effectively use Enterprise JavaBeans, you need to understand the EJB architecture, so this book includes two chapters on the subject. This chapter explores the core of EJB: how enterprise beans are distributed as business objects. Chapter 3 explores the services and resource-management techniques supported by EJB.
To be truly versatile, the EJB component design had to be smart. For application developers, assembling enterprise beans is simple, requiring little or no expertise in the complex system-level issues that often plague three-tier development efforts. While EJB makes the process easy for application developers, it also provides system developers (the people who write EJB servers) with a great deal of flexibility in how they support the EJB specification.
The similarities among different CTMs allow the EJB abstraction to be a standard component model for all of them. Each vendor’s CTM is implemented differently, but they all support the same primary services and similar resource-management techniques. These services and techniques are covered in more detail in Chapter 3, but some of the infrastructure for supporting them is addressed in this chapter.
Enterprise JavaBeans server-side components come in three fundamentally ...