I've very basic (novice) knowledge about EJB 2.1 and I'm totally new to EJB 3.0 concepts, but I've keen interest to learn it the best way. So my question is - Should I've in-depth knowledge about EJB 2.1 before starting to learn about EJB 3.0? If not, can i relate the concepts first hand starting with EJB 3.0??
I don't know EJB 2.1 in detail but I know the basics like you. And in my opinion EJB 3.0 is so much different that it wouldn't be helpful to know EJB 2.x before. EJB 3.0 is much easier to use for the developer so it would just be more work to waste your time with EJB 2.x at first. The only reason to learn EJB 2.x today is probably if you have to maintain older applications which are developed with EJB 2.x for historical reasons.
Besides the technical issues it will of course help you if you already have some knowledge on enterprise applications in general regardless of the technology used. But the basic idea behind all this is the same with EJB 2.x, EJB 3 or even .NET.