private String _postLink(String objectId, URL link, String message)
            throws FacebookException {
        HttpParameter[] httpParameters = {new HttpParameter("link", link.toString())};
        if (message != null) {
            httpParameters = HttpParameter.merge(
                                httpParameters,
                                new HttpParameter[]{new HttpParameter("message", message)}
                             );
        }
        JSONObject json = post(buildEndpoint(objectId, "feed"), httpParameters)
                          .asJSONObject();
        try {
            return json.getString("id");
        } catch (JSONException jsone) {
            throw new FacebookException(jsone.getMessage(), jsone);
        }
    }