Weblogic 8.1 is compliant to J2EE 1.3 specifications. J2EE 1.3 specs include EJB 2.0 specs and not EJB 2.1
So if you want to write EJB 2.1 code better use Weblogic 9.0 server if you are particularly interested in BEA products.
Mastering EJB 3rd Edition by Ed Roman is freely downloadable from
TheServerSide.com and is a good material to learn EJB 2.1