Head First EJB

Chapter 1. Intro to EJB: Welcome to EJB

Enterprise JavaBeans are easy. Well, at least when you compare EJB to what you’d have to do to write your own scalable, transactional, secure, concurrent enterprise server. In this chapter, we’ll develop, deploy, and run an EJB application, before diving into the details. Before we’re done, we’ll look at the use, benefits, and characteristics of EJB, and we’ll look (briefly) at how EJB containers work. We’ll take a high-level look at the architecture of EJB and learn about the three bean types. The more you understand from this chapter, the less you’ll have to memorize later, so don’t skip it. (If you’re an EJB expert, you can probably get away with just a quick skim.)

Objectives

Enterprise Javabeans Overview

Official:		What it really means:
1.1	Identify the use, benefits, and characteristics of Enterprise Javabeans technology, for version 2.0 of the EJB specification.	You need to know how EJB works overall, what it’s good for, what it provides, and what it doesn’t provide. You need to understand the overall architecture of EJB and how that architecture supports the features of EJB. For example, you need to know that EJB supports transactions, security, and concurrency, but it does not guarantee load-balancing, fail-over, or clustering. You need to know that EJB supports three bean types: session, entity, and message-driven, and that session beans can be stateless or stateful.