@Reference(name = REFERENCE_LIBRARY, service = Library.class)
    protected void setLibrary(ServiceReference<Library> ref) {
        libraryRef.setReference(ref);
    }
@ Reference ( name = REFERENCE_LIBRARY , service = Library . class ) protected void setLibrary ( ServiceReference < Library > ref ) { libraryRef . setReference ( ref ) ; }
The reference target is specified via metatype