weblogic.xml is not required for an application to be deployed to WL. At least for WL10 and I think it was the same for WL7, I can't speak to any other versions. I have several apps deployed to WL, some use it some don't. It's for setting some WL specific configs and some other configs which are not necessarrily WL specific. Some of them can even be set by other means if I'm not mistaken. If you are trying to deploy to WL and it is complaining about not having a weblogic.xml then I suspect Netbeans is setting something in your project build archive which is in turn instructing WL to look for weblogic.xml on deployment. All
JEE app-servers typically have some server specific config files which can be included in the app archive, though they are not necessarrily required.