Titanium multipart file upload with different content types? - rest

Question

So I am trying to post to a Salesforce.com REST api that is expecting the following sample request -
POST /services/data/v33.0/chatter/feed-elements HTTP/1.1
Authorization: OAuth 00DRR0000000N0g!...
User-Agent: Jakarta Commons-HttpClient/3.0.1
Host: instance_name
Content-Length: 845
Content-Type: multipart/form-data; boundary=a7V4kRcFA8E79pivMuV2tukQ85cmNKeoEgJgq
Accept: application/json
--a7V4kRcFA8E79pivMuV2tukQ85cmNKeoEgJgq
Content-Disposition: form-data; name="json"
Content-Type: application/json; charset=UTF-8
{
"body":{
"messageSegments":[
{
"type":"Text",
"text":"Please accept this receipt."
}
]
},
"capabilities":{
"content":{
"description":"Receipt for expenses",
"title":"receipt.pdf"
}
},
"feedElementType":"FeedItem",
"subjectId":"005RR000000DmOb"
}
--a7V4kRcFA8E79pivMuV2tukQ85cmNKeoEgJgq
Content-Disposition: form-data; name="feedElementFileUpload"; filename="receipt.pdf"
Content-Type: application/octet-stream; charset=ISO-8859-1
...contents of receipt.pdf...
--a7V4kRcFA8E79pivMuV2tukQ85cmNKeoEgJgq--
As you can see, the two parts of the request is expecting different content types.
In Titanium, I have the following code -
xhr.open("POST", postUri);
xhr.setRequestHeader("Authorization", authHeader);
xhr.setRequestHeader('enctype', 'multipart/form-data');
var data2send = {
json: jsonObj,
feedElementFileUpload: imageBlob
};
xhr.send(data2send);
According to the Appcelerator documentation and a couple of online threads, the httpclient should be able to set each part automatically, however, Salesforce API still gives an error message of:
[{"errorCode":"MISSING_ARGUMENT","message":"Missing required 'subjectId' parameter."}]
I can confirm that subjectId is in the jsonObj and its content is correct. It seems that the json part is not recognised as JSON by Salesforce correctly. How can I set the content-type correctly? Many thanks.
Updates - I used the Wireshark to capture the request text. Apparently the httpclient did not set up the content-type for the json part that Salsforce API is expecting. Any idea how to set it?
POST /services/data/v33.0/chatter/feed-elements HTTP/1.1
Host: mydomain.com
Accept-Language: en-us
User-Agent: Appcelerator Titanium/3.5.1 (iPhone Simulator/8.2; iPhone OS; en_US;)
enctype: multipart/form-data
X-Requested-With: XMLHttpRequest
Accept: */*
Content-Type: multipart/form-data; charset=utf-8; boundary=0xTibOuNdArY_1430987526
Connection: keep-alive
Authorization: Bearer $My_AUTH_CODE
X-Titanium-Id: 8329dd1d-3379-4d7c-955e-120ad1586a2b
Content-Length: 93333
Accept-Encoding: gzip, deflate
--0xTibOuNdArY_1430987526
Content-Disposition: form-data; name="json"
{"feedElementType":"FeedItem","subjectId":"xxxxxxxxxx","body":{"messageSegments":[{"type":"text","text":"test"}]},"capabilities":{"content":{"description":"sdfaadfs","title":"adsfafsd.png"}}}
--0xTibOuNdArY_1430987526
Content-Disposition: form-data; name="feedElementFileUpload"; filename="01430987526.png"
Content-Type: image/png
my file data...