public String requestOkHttp(String url, String method, String json) throws IOException {
        RequestBody requestBody;
        requestBody = METHOD_POST.equals(method) || METHOD_PUT.equals(method) ?
                RequestBody.create(JSON, json == null ? "" : json) : null;

        okhttp3.Request.Builder requestBuilder = new okhttp3.Request.Builder()
                .url(url);

        requestBuilder.method(method, requestBody);

        OkHttpClient client = new OkHttpClient();

        Response response = client.newCall(requestBuilder.build()).execute();
        return response.body().string();
    }