Have you tried the JBoss graphical installer? It allows you to pick and choose which components you want installed. Our JBoss 4.0.x full testsuite runs with a 64M Heap size and that's WITH EJB.
Also, check out our Embeddable EJB3 stuff. We have JNDI, JMS, TM, JDBC Connections running outside of the app server, along with EJB3. We don't have the full stack yet (no remoting capabilities), but the end goal is to have Embeddable JBoss stack so that you can mix and match what you want, in and out of the application server.
We're not 100% or even 75% percent there for a "lightweight" container, but we're moving in that direction.
BTW, what are your "lightweight" requirements? Do you have actual memory/hardware constraints? Or have you been reading too many blogs or "Lighter, faster, smarter" Java Books?
Thank you for the answers on both threads (this one and the JMX question). I will combine my replies to this one.
I went over the EJB 3 webex and it looks promising. I really like the POJO approach and the service EJB notion. I also went over the Embeddable EJB 3.0 documentation.
In your answer you don't mention JMX as part of the Embeddable EJB 3.0, yet there is the @management directive that is mentioned for the service EJB. Is it only part of the JBoss AS 5.0 offering and not part of the Embeddable EJB 3.0? Also will it support cluster functionality (LB/FT) throught the MicroContainer?
Regardless, I didnt try the graphical installer and I plan to do just that later today.
As for our "lightweight" requirements, we have resources constraints in that we seek to run multiple containers on one machine (we did read too much of the "lighter,smarter,faster" stuff). We have a really big enterprise application and we try to make is as much scalable by hardware as possible. We have a specific requirement for "big" servers deployment where each will have a ton of memory and a bunch of CPUs. From our experience it is better to run each group of services in a different JVM/container (due to stability and memory constraints). We also got to the point where most of our back-end is none EJB. So we seek the best solution for a lightweight POJO AS.
What would really help me - if may ask for that - is a list of planned layers for the Embeddable EJB 3.0 project (anything planned for 5.0), including the MicroContainer layers (clustering?). And a list of layers that will only be avaialble through JBoss AS usage.