Pradeep,
You can use AspectJ wherever you see crosscutting concerns in
Java (and that is pretty much every project!). That said, in certain environment, particularly J2ME, AspectJ may not work out of the box.
Tina,
AspectJ is integrated with BEA Weblogic (see
http://dev2dev.bea.com/resourcelibrary/utilitiestools/monitoring.jsp). However, on most cases, you can use AspectJ without such integration.
-Ramnivas