futures.java

    private static Future<String> requestJson(final String uri) {
        return Future.create(new Callable<String>() {
            public String call() throws IOException {
                OkHttpClient client = new OkHttpClient();
                HttpURLConnection conn = client.open(new URL(uri));
                InputStreamReader in =
                        new InputStreamReader(conn.getInputStream(), "utf-8");
                try {
                    return CharStreams.toString(in);
                } finally {
                    in.close();
                    conn.disconnect();
                }
            }

        });
    }

    public Future<Config> getConfig() {
        return requestJson(CONFIG).map(new Function<String,Config>() {
            public Config apply(String in) {
                Gson gson = new Gson();
                Config.Envelope envelope =  gson.fromJson(in, Config.Envelope.class);
                return envelope.result;
            }
        });
    }