Historically, generating RPMs for the wrappers was a complicated process, because generation of java wrappers was strongly coupled to building the library. Now it's no longer so, and the two processes are now totally independent, which means that you can build RPMs for java wrappers normally as for any other gnustep package - in the simple, standard way - just add PACKAGE_NAME and VERSION to your GNUmakefile, and provide corresponding .spec.in and .debug.spec.in files.