there are a lot of technologies  involved, but I
just want to mention that j2ee  is not equal to EJB. this is a trap
which most new commers fall into. ejb is a very important  technology
in j2ee but it has also some alternatives like JDO and JavaSpaces.
the importance of the technologies depends on nature of your project.
it is not that much elegant to use a tank to kill a mouse!