public String postGroupLink(String groupId, URL linkURL, String message) throws FacebookException {
        ensureAuthorizationEnabled();
        HttpParameter[] httpParameters = new HttpParameter[]{new HttpParameter("link", linkURL.toString())};
        if (message != null) {
            httpParameters = HttpParameter.merge(httpParameters,
                                new HttpParameter[] {new HttpParameter("message", message)});
        }
        JSONObject json = post(buildEndpoint(groupId, "feed"), httpParameters).asJSONObject();
        return getRawString("id", json);
    }