Chapter 2. Enterprise JavaBeans Overview

Topics in This Chapter

• The J2EE Architecture

• J2EE Components

• J2EE Application Server

• Session Bean Overview

• Entity Bean Overview

• Message-Driven Bean Overview

• Local Interfaces

This chapter presents an overview of the J2EE architecture and Enterprise JavaBeans architecture. We'll begin with the concepts behind the J2EE architecture and how the J2EE components help you design distributed applications. Next, we'll discuss the J2EE application server and the role of the container in each server. This helps you understand how enterprise beans fit into the big picture.

There's a lot of terminology that goes along with enterprise beans, so this chapter is a good place to define terms. We'll start with the concepts behind session beans (stateless and stateful), entity beans, and message-driven beans. We'll help you understand how entity beans with bean-managed and container-managed persistence interact with a database. You'll also learn about bean life cycles, entity relationships, interfaces (home, local home, remote, and local) and asynchronous messaging.

This chapter is meant as an overview, so some of the topic discussions will be brief. Others will be explained in more detail. There will, of course, be much more to talk about when we start designing enterprise systems in later chapters. Let's start with the J2EE architecture, which is the foundation of enterprise beans.