What is an Enterprise Java Bean really?

Question

On the Tomcat FAQ it says: \"Tomcat is not an EJB server. Tomcat is not a full J2EE server.\"

But if I:

• use Spring to supply an application context
<

Answer 1

Indeed, if you put enough effort you can almost turn Tomcat/Spring into a full-fledged heavyweight application server :) You could even embed a portable EJB3 container...

What is it that a Java EE compliant app server gives you that you can't easily/readily get from Tomcat with some 3rd party subsystems?

There are still a few features that are hard to get with 3rd party modules:

• stateful session beans (SFSB)
• extended persistence context
• application client container / java web start
• clustering depending on the app. server
• CORBA interoperability
• JCA integration ~
• remoting ~
• container-managed transactions ~
• decent management of distributed transactions (e.g. recover heuristic tx)

Entries with ~ are also supported by Spring, but not so trivially, at least to my best knowledge.

A few more details in this answer: EJB vs Spring