HttpURLConnection post json

public Object createCouponShop(){
    String access_token = getAccess_token();
    String userListUrl="https://api.weixin.qq.com/card/landingpage/create?access_token="+access_token;
    String message;
    try  {
       URL url = new URL(userListUrl);
       HttpURLConnection http = (HttpURLConnection)url.openConnection();
       http.setRequestMethod("POST");
       http.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
       http.setDoOutput(true);
       http.setDoInput(true);
       System.setProperty("sun.net.client.defaultConnectTimeout", "30000");
       System.setProperty("sun.net.client.defaultReadTimeout", "30000");
       
       http.connect();
       DataOutputStream out = new DataOutputStream(
                    http.getOutputStream());
            String json="{\"banner\":\"http://pic.58pic.com/01/18/39/61bOOOPICdf.jpg\",\"page_title\":\"one year celebration coupon\",\"can_share\":false,\"scene\":\"SCENE_H5\",\"card_list\":[{\"card_id\":\"po7-6jl4t2OlINSjMMYvhBLKR8j0\",\"thumb_url\":\"http://pic.58pic.com/01/18/39/61bOOOPICdf.jpg\"}]}";


            out.writeBytes(json);
            out.flush();
            out.close();
       
       InputStream is = http.getInputStream();
       int size = is.available();
       byte jsonBytes[] = new byte[size];
       is.read(jsonBytes);
       message = new String(jsonBytes, "UTF-8");
       
       return "CouponTest response:" + message;
        } catch (Exception e) {
        e.printStackTrace();
        message = e.toString();
        }
        return message;
    }