SAP web App server J2EE applications

Generally what kind of J2EE applications are developed and deployed to SAP web App Server? Can anyone give some examples of applications they deployed in web app server. If we have SAP enterprise portal for web application then what is the need for J2EE development? I'm confused or may be i'm missing some thing.

Any documents or material on SAP WAS would be appreciated.

Also,I would appreciate if anyone gives me step by step guides for deploying and undeploying a web application(EAR file) to web app server.

Thanks,

Kalpana

kalpana_govindarajan@yahoo.com