Non-matched part of the URL is exposed as a request attribute named HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE
:
@RequestMapping("/{id}/**")
public void foo(@PathVariable("id") int id, HttpServletRequest request) {
String restOfTheUrl = new AntPathMatcher().extractPathWithinPattern(request.getAttribute(HandlerMapping.BEST_MATCHING_PATTERN_ATTRIBUTE).toString(),request.getRequestURI());
...
}