If you use Eclipse IDE, please right click to web project:
Properties -> Deployment Assembly
and check your deployment assembly list.
For example I have this list in my Deployment Assembly:
src/main/java | WEB-INF/classes
src/main/resources | WEB-INF/classes
src/main/... | WEB-INF/web.xml
I deledet web.xml row because the WebLogic supported WEB-INF/classes. Here is an explanation:
If you are mapping external folders to web resources in Deployment Assembly, NOT all the mappings are supported, only resource folder mapping to EAR or web content root are supported in split source. (In your case, mapping to '/WEB-INF/classes/' should be supported, which is a bug we will fix in future release)