The documentation here:
lists examples for the http://, https://, file://, classpath:// and internal:// schemes, but should give detail on when you would use which scheme. The internal:// scheme is the one that could be most confusing to readers.
Additionally, there is a typo on the classpath:// example.
classpath://META-INF/HelloWorldWS.wsdl should instead be classpath:///META-INF/HelloWorldWS.wsdl (with 3 slashes). The "classpath://" prefix is chopped off during parsing, and 1 more slash is needed for absolute classpath resource loading, otherwise relative classpath resource loading is employed. This is NOT a bug - it was intended to work that way - but the documentation should be updated.