EJB Technology Overview

The Enterprise JavaBeans (EJB) specification defines a server-side component technology designed to support the construction of distributed enterprise-class applications. We ll break apart the definition of EJB and examine key concepts:

EJB is a specification.    It is not a set of classes, code, or reference implementation components . Vendors such as BEA are expected to build application servers that implement EJB technology according to that specification.

EJB is a component technology.    Component technologies emphasize the encapsulation of business logic in components deployed and managed in a container . The EJB specification carefully defines the interactions between components and their containers to ensure portability and consistency between EJB container vendors.

EJB supports distributed applications.    EJB components may be distributed across multiple servers or processes with a limited impact on component developers, a concept known as location transparency .

EJB is designed for enterprise-class applications.    The EJB specification is very concerned with transactions, security, concurrency, and memory management because these areas are important for large, mission-critical applications.

To remain consistent with the target audience for this book, intermediate- to advanced-level developers and architects , we will not discuss the basic development approach for EJB components. We assume that you have already built some simple EJB components and are familiar with the key steps and concepts involved, and that you would rather learn about more advanced topics and best practices for developing EJB applications.

The next chapter discusses the development and packaging of the bigrez.com example EJB application and will cover some of the tools and best practices related to the development process. Chapter 13 is also dedicated to development best practices, so there is no lack of information on this topic in this book.