multipart data POST using python requests: no multipart boundary was found

Question

I have a form-data as well as file to be sent in the same POST. For ex, {duration: 2000, file: test.wav}. I saw the many threads here on multipart/form-data posting using python requests. They were useful, especially this one.

My sample request is as below:

    files = {'file': ('wavfile', open(filename, 'rb'))}
    data = {'duration': duration}
    headers = {'content-type': 'multipart/form-data'}
    r = self.session.post(url, files=files, data=data, headers=headers)

But when I execute the above code, I get this error:

5:59:55.338 Dbg 09900 [DEBUG] Resolving exception from handler [null]: org.springframework.web.multipart.MultipartException: Could not parse multipart servlet request; nested exception is org.apache.commons.fileupload.FileUploadException: the request was rejected because no multipart boundary was found.

So my questions are: 1) How can I see the content of the request being sent? Couldn't use wireshark, its not across the network. 2) why is the boundary missing in the encoded data? Did I miss anything, please point out.

Answer 1

You should NEVER set that header yourself. We set the header properly with the boundary. If you set that header, we won't and your server won't know what boundary to expect (since it is added to the header). Remove your custom Content-Type header and you'll be fine.

Answer 2

Taking out the Content-Type header with explicit "multipart/form-data" worked!

Answer 3

To specifically add boundary add following in header :

headers = {
    'content-type': 'multipart/form-data; boundary=ebf9f03029db4c2799ae16b5428b06bd'
}