Apache HttpClient include boundary in multipart/form-data

[Arya F]

I made a post about this on Stackoverflow and never received an answer.
Here is the link to the post
https://stackoverflow.com/questions/48994951/apache-httpclient-include-boundary-in-multipart-form-data

Here is what I am stuck on

I have the following POST request which is supposed to upload a file. But I
can not figure out how to include the boundary in the request for the
"Content-Type" header.


HttpPost request = new HttpPost(url);
request.setConfig(config);

StringEntity params = new StringEntity("");

HttpEntity entity = MultipartEntityBuilder.create()
        .addBinaryBody("blob", file,
ContentType.create("application/octet-stream"), "filename").build();

request.addHeader("Host", "upload.twitter.com");
request.addHeader("Connection", "keep-alive");
request.addHeader("User-Agent", userAgent);
request.addHeader("Content-Type",  ????????);
request.addHeader("Accept", "*/*");
request.addHeader("Accept-Encoding", "gzip, deflate, br");
request.addHeader("Accept-Language", "en-US,en;q=0.9");
request.addHeader("Cookie", cookies);

request.setEntity(entity);
response = httpClient.execute(request);

int responseCode = response.getStatusLine().getStatusCode();

System.out.println("upload response code: " + responseCode);



any idea how this is done?