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Chapter 1 What’s what in EJB 3.0
One day, when God was looking over his creatures, he noticed a boy named Sadhu whose humor
and cleverness pleased him. God felt generous that day and granted Sadhu three wishes. Sadhu asked
for three reincarnations--one as a ladybug, one as an elephant, and the last as a cow. Surprised by
these wishes, God asked Sadhu to explain himself. The boy replied, "I want to be a ladybug so that
everyone in the world will admire me for my beauty and forgive the fact that I do no work. Being an
elephant will be fun because I can gobble down enormous amounts of food without being ridiculed. I
will like being a cow the best because I will be loved by all and useful to mankind." God was charmed
by these answers and allowed Sadhu to live through the three incarnations. He then made Sadhu a
morning star for his service to mankind as a cow.
EJB too has lived through three incarnations. When it was first released, the industry was dazzled
by its innovations. But like the ladybug, EJB 1 had limited functionality. The second EJB
incarnation was just about as heavy as the largest of our beloved pachyderms. The brave souls who
could not do without its elephant-power had to tame the awesome complexity of EJB 2. And finally,
in its third incarnation, EJB has become much more useful to the huddled masses, just like the gentle
bovine that is sacred for Hindus and respected as a mother whose milk feeds us all..
A lot of people have put in a lot of hard work to make EJB 3 as simple and lightweight as
possible without sacrificing enterprise-ready power. EJB components are now little more than Plain
Old Java Objects (POJOs) that look a lot like code in a Hello World program. We hope you will
agree with us as you read through the next Chapters that it has all the makings of a star.
We’ve strived to keep this book as earthy as possible without skimping on content. The book is
designed to help you learn EJB 3.0 as quickly and as easily as possible. At the same time, we will not
neglect to cover the basics where needed. We will also dive into deep waters with you where we can,
share with you all the amazing sights we’ve discovered and warn you about any lurking dangers.
This book is about the radical transformation of a very important and uniquely influential
technology in the Java World. We suspect you are not picking this book up to learn too much about
EJB 2. You probably either already know EJB 2.x or are completely new to the world of EJB. In
either case, spending too much time on previous versions is a waste of your time --you won't be
surprised to learn that EJB 3.0 and EJB 2.x have very little in common. . If you are really curious
about the journey that brought us to the current point, we encourage you to pick up one of the many
good books on the previous versions of EJB.
Our goal in this Chapter is to tell you what’s what in EJB 3.0, why you should consider using it,
and, for EJB 2.x veterans, outline the significant improvements the newest version offers. We will
then jump right into code in the next Chapter to build on the momentum of this one. With this goal
in mind, we now start with a broad overview of EJB.
1.1 EJB Overview
In very straightforward terms, Enterprise Java Beans (EJB) is a platform for building portable,
reusable and scalable business applications using Java programming language. Since its initial
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yangyunqi20112011-10-11已经打印再看了，很不错，和原来EJB2.0比较着看，收获会很大
chungsinwei2012-04-23The book is quite complete, well written, with good examples. It is a very valuable tool to enter the ejb3 world
