Add Source File To Exist Project Error "VALIDATION_EXCEPTION"

Hi Everyone.

I got trouble when using API to upload source file to Exist Project.

I'm using below API to upload source file.

RWS Language Cloud API Documentation (

My source to create request.

private HttpURLConnection httpConn;
private DataOutputStream request;
private final String boundary = "*****";
private final String crlf = "\r\n";
private final String twoHyphens = "--";

// First part of request
public MultipartUtility(String requestURL, String token, String userId)
throws IOException {
     // creates a unique boundary based on time stamp
     URL url = new URL(requestURL);
     httpConn = (HttpURLConnection) url.openConnection();
     httpConn.setDoOutput(true); // indicates POST method

     httpConn.setRequestProperty("X-LC-Tenant", "LC-" + userId);
     httpConn.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + this.boundary);
     httpConn.setRequestProperty("Accept", "application/json");
     httpConn.setRequestProperty("Authorization", "Bearer "+ token);
     httpConn.setRequestProperty("Connection", "Keep-Alive");
     System.setProperty("https.protocols", "TLSv1,TLSv1.1,TLSv1.2");
     request = new DataOutputStream(httpConn.getOutputStream());

// Add name="file" to form-data
public void addFilePart(String fieldName, File uploadFile) throws IOException {
     String fileName = uploadFile.getName();
     request.writeBytes(this.twoHyphens + this.boundary + this.crlf);
     request.writeBytes("Content-Disposition: form-data; name=\""
     + fieldName + "\"; filename*=UTF-8''\""
     + URLEncoder.encode(fileName, "UTF-8") + "\"" + this.crlf);

     byte[] bytes = Files.readAllBytes(uploadFile.toPath());

// Add name="properties" to form-data
public void addFormField(String name, String value) throws IOException {
     request.writeBytes(this.twoHyphens + this.boundary + this.crlf);
     request.writeBytes("Content-Disposition: form-data; name=\"" + name + "\"" + this.crlf);
     request.writeBytes("Content-Type: text; charset=UTF-8" + this.crlf);
     request.writeBytes(value + this.crlf);

// End of request
public HttpURLConnection finishing() throws IOException {
     request.writeBytes(this.twoHyphens + this.boundary + this.twoHyphens + this.crlf);
     return httpConn;

BUT, I get below error.

{"errorCode":"VALIDATION_EXCEPTION","message":"Invalid multipart request, either boundary missing or malformed, or missing file parameter!","details":[]}

Please tell me, What wrong with abow code. Please