Is HttpServletRequest.getRequestURL() spoofable?

The question is self explanatory, I hope. I am setting up a Spring Security enviroment with a CAS-server. Because the exact same application is deployed on the same server, but the server is accessible via different host names (.de domain, .com domain, possibly more than that) and we want to deploy the same application on test systems and the local one as well, I built a dynamic service, where the service URL is derived from request URL.

public static String makeDynamicUrlFromRequest(ServiceProperties serviceProperties, HttpServletRequest request) {
        String serviceUrl = "http://ift.tt/1FJUxOX";
        URI uri = null;
        try {
            uri = new URI(request.getRequestURL().toString());
        } catch (URISyntaxException e) {
            logger.error("Someone tried accessing a disallowed service!", e);
        }

        if(uri != null){
            serviceUrl = uri.getScheme() + "://" + uri.getHost() + "/login";
        }

        return serviceUrl;
    }

Is it possible to spoof this? If it is, does an additional regex-check provide me with the necessary security against this?