Difference between Java Bean and Enterprise Java Beans?

A JavaBean is just a plain old Java object that conforms to certain conventions including the use of accessor functions (getFoo/setFoo) for member access, provision of a default constructor and a few other things like that.

An Enterprise JavaBean is a component in a Java EE application server which comes in several flavours, the details of which vary by which version of Java EE you're talking about (or, more specifically, which specific set of EJB specifications are involved).

JavaBeans were originally mostly intended to be used in builder tools by providing a known interface which could be looked for through introspection in the tools. They quickly turned into what amounts to a religion, however.

Enterprise JavaBeans are intended to provide encapsulated business logic for enterprise applications within a general container that provided things like session management, security, resource pooling, etc. as services thus allowing the business logic to be (relatively) untainted by these cross-cutting concerns. (Whether or not they accomplished this is a matter that is up for debate, given how difficult they were to use at first. More recent versions of the specification have made this easier, however. Legacy apps, though, are still a pain and sadly likely the majority of the EJBs you're likely to encounter.)

Edited to add:

You can read the EJB API right here: http://java.sun.com/products/ejb/javadoc-3_0-fr/
You can read the full specification of a JavaBean right here: http://java.sun.com/javase/6/docs/api/java/beans/package-summary.html

I was just about to finish an almost identical answer but you beat it to me so I decided to +1 instead. Good work.

Fredrik 2010-03-17 05:30:34

Thanks. I'd have been interested, however, in seeing your take on it. I always like to read others' perspectives on information.

JUST MY correct OPINION 2010-03-17 05:34:57

@ttmrichter: Well, you covered it all and few more things so my takes wasn't really worth publishing. The only thing I think is missing was a confusing attempt to describe MDB, CMP and session beans but I wasn't really happy with the attempt so it is just as good.

Fredrik 2010-03-17 05:50:24

+1 for JavaBean explanation -1 for EJB explanation. Less buzzwords please!

allyourcode 2010-03-17 06:03:46

It's hard (perhaps impossible) to explain EJBs without buzzwords because as far as I can tell their creation and use centres almost exclusively on buzzwords! :D

JUST MY correct OPINION 2010-03-17 09:43:57

@ttmrichter. Don't agree about the necessary buzzword. You can summarize it like this: java bean is a naming convention, EJB is component *model*. That's the heart of the difference, you didn't emphasized that enough in my sense. See my answer.

ewernli 2010-03-17 09:50:24

First JavaBeans is a lot more than a naming convention. Check out the link I provided above. It's just that the naming convention is the part that stuck.Second, "component model" is also buzzword-ish. It doesn't explain what the model in question is intended to accomplish (you covered the network code in your question, but not the session management, the persistence, the security, etc. etc. etc.).Really, I don't think there is an easy answer to "what is an Enterprise JavaBean" (aside from "a horrible name"). Trying to do this results in jargon and buzzwords.

JUST MY correct OPINION 2010-03-17 10:20:27

+1 you convinced me :) (Though I would still argue that what the component model provides exactly is not what matter the most if you want to understand the big picture behind EJB. You just need to understand it's a component model, like CORBA, COM, or others. But yes, you need to know what a component model is in general which most of the time isn't the case.)

ewernli 2010-03-17 10:47:46

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Difference between Java Bean and Enterprise Java Beans?

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