Introduction

With the introduction of Java in the mid-1990s, its portability was obvious on the client side. Java has quickly become the language of choice for writing applications. Most browsers support Java, and Java applets and Java applications can run on any machine or operating system. But this is not enough for enterprise applications, which require server-side Java support. Writing applications for the enterprise is usually a difficult task. Enterprise applications must be scalable, portable, and secure. That's what Java 2 Platform, Enterprise Edition (J2EE) is all about: a complete architecture and framework for developing and deploying server-side Java components. Enterprise JavaBeans (EJB) is the heart of the J2EE platform. It enables simplified development of distributed Java applications. Other J2EE run-time services, such as JNDI, JDBC, and JMS, are vital in completing the full picture of server-side component architecture.

Since the EJB 1.0 specification was introduced by Sun Microsystems in 1998, it quickly gained industry momentum among application developers and vendors. Today, more than 25 application server vendors support EJB technology in their products. Charles Stack, president and CEO of Flashline, states, “The EJB component architecture allows vendors to simplify application development, [and] speed the delivery of high-quality products to market…The market for commercial EJB technology-based components is rapidly growing as more corporations adopt the J2EE platform as their primary development architecture.” More than 20 companies collaborated with Sun Microsystems to finalize the EJB 2.0 specification in 2001. This demonstrates the industry's support of and commitment to building enterprise applications using EJB technology.

This book focuses primarily on teaching the EJB technology, but it also covers other J2EE technologies that are essential to understanding EJBs. You'll be introduced to all aspects of EJB development using the most current version of the specification.

The book helps you learn concepts and the reasoning behind them by using simple, under-the-hood diagrams. In addition, it focuses on step-by-step instructions for developing components and then running them.

You'll learn how to write portable applications that can run on multiple application servers and databases. For demonstration purposes, we provide step-by-step instructions for running the examples in two different application servers: WebLogic Server and JBoss. WebLogic Server is the most widely used commercial application server today, and JBoss is an emerging open source, small footprint, J2EE application server. We also use multiple databases: Pointbase (a lightweight Java database to run the examples with WebLogic Server) and Hypersonic (to run the same examples with JBoss).

This book does not depend on any Java development tools or IDEs. It requires only the use of a text editor. You'll be introduced to all aspects of developing, compiling, packaging, deploying, and running your components and applications in easy and simple methods. By the time you're done with this book, you'll be acquainted with the reasons why EJB is the choice of serious enterprise application developers.