Service Now upload attachment using java httpUrlConnection rejected large rest payload error

Question

I am getting the below error while uploading attachment for an incident in service now.

"error":{"detail":"Rejected large REST payload with content-length = 13011091 bytes. Max allowed: 10485760 bytes.","message":"Exception while reading request"},"status":"failure"}

Below is the code:

   JSONObject AttachmentData = new JSONObject();
    AttachmentData.put("agent", this.getAgent());
    AttachmentData.put("topic", this.getTopic());
    AttachmentData.put("name", this.getName());
    AttachmentData.put("source", this.getSource());
    AttachmentData.put("payload", this.getPayload());
    try {
        AuthenticationSNOWInfo auth = new AuthenticationSNOWInfo(sysDomain);
        String UserId = auth.getUserId();
        String Password = auth.getPassword();

        if (this.webServiceAddress != null && !this.webServiceAddress.equalsIgnoreCase("")) {
            logger.debug("Calling webservice:  " + this.webServiceAddress);
            snowLogger.debug("Calling webservice: " + this.webServiceAddress);
            url = new URL(this.webServiceAddress);
            conn = (HttpURLConnection) url.openConnection();
            String encoded = java.util.Base64.getEncoder()
                    .encodeToString((UserId + ":" + Password).getBytes(StandardCharsets.UTF_8));

            conn.setDoOutput(true);
            conn.setRequestMethod("POST");
            conn.setRequestProperty("Authorization", "Basic " + encoded);
            conn.setRequestProperty("Content-Type", "application/json");
            conn.setRequestProperty("Accept", "application/json");
            OutputStream os = conn.getOutputStream();
            os.write(AttachmentData.toString().getBytes(StandardCharsets.UTF_8));
            os.flush();

            BufferedReader br;
            logger.debug(conn.getResponseCode());
            if (conn.getResponseCode() > 199 && conn.getResponseCode() < 300) {
                br = new BufferedReader(new InputStreamReader((conn.getInputStream()),StandardCharsets.UTF_8));
            } else {
                br = new BufferedReader(new InputStreamReader((conn.getErrorStream()),StandardCharsets.UTF_8));
            }
            returnJSON = br.readLine();