how you going to deploy it...
if you deploying taskflow then you can deploy as .jar file..
otherwise you .ear file to deploy on the system...
If you start your project as fusion web application the deployment descriptor are build by the framework in each project and the application for the ear file you deploy to the server for the application.
Check the project properties deployment node.
If you are talking about reusable adf jars you choose ADF library as descriptor.
And please tell us your Jdev version.
we're using 18.104.22.168