Android Http Post to REST Api

Hi I'm primarily an Android developer and am pretty clueless about http protocols, you help would be much appreciated!

I am trying to make an api call to this: where I POST a file on the device.

They give a sample request of:

POST /api/assignments/3/submit

And in the description state that the files param is:

Array of files with each element containing a hash of filename and base64 encoded file

This is the code that I'm trying right now (note: I'm using Robospice + Spring for Android):

   File file = new File(Environment.getExternalStorageDirectory() +
        Base64InputStream stream = new Base64InputStream(new FileInputStream(file), 0);
        HttpHeaders headers = new HttpHeaders();
        headers.add("x-haiku-auth", HaikuAPI.getAuthHeader());
        MultiValueMap<String, Object> parts = new LinkedMultiValueMap<String, Object>();
        parts.add("files[][file]", parts);
        HttpEntity<Object> request = new HttpEntity<Object>(stream, headers);
        UriComponentsBuilder builder = UriComponentsBuilder
                        "https://" + HaikuAPI.getDomain() + "/api/assignments")
                .pathSegment(assignmentID + "", "submit")
                .queryParam("message[subject]", "Assignment Completed")

                .queryParam("message[body]", message)
                .queryParam("message[assignment_id]", assignmentID)
                .queryParam("files[][filename]", "test.jpg");

        URI url =;

        String response = getRestTemplate().postForObject(url, request, String.class);
        return response;

But I get an error saying that it can't serialize the stream to JSON. Following the API documentation do I have to place the stream as a param? Also what is the correct way to implement this? I would love if I didn't have to put a file size limit on the user, hence the streams. Though I have gotten it to work with small files encoded in Base64 and placed directly as a param...

Any help is greatly appreciated! I will definitely not downvote comments or answers for small pointers.


Updated code, but still get another error message:

00:25:50.904 Thread-2066 An exception occurred during request network execution :Could not write request: no suitable HttpMessageConverter found for request type [org.springframework.util.LinkedMultiValueMap] and content type [application/x-www-form-urlencoded]


Looks like you're using Spring for Android. Judging that error message it seems Spring forces the content type to be application/json, while I believe you're trying to send application/x-www-form-urlencoded. So set this Content-Type header:


Spring will know then to match the proper MessageConverter. More info on this here.

EDIT: Also, you're supposed to send the request data in POST data, not in request URI. Move that to a MultiValuesMap. Have a look at the link I gave you how to post such data. A complete documentation on these can also be found here.

EDIT2 You need to set the MessageConverter for your response as well. Something like:

List<MediaType> acceptableMediaTypes = new ArrayList<MediaType>();

EDIT3 If you need to send files, consider using Resource, to be more specific InputStreamResource. But there is a trick: you need to provide the file name and the file size, otherwise your request will crash. Something like:

Resource res = new InputStreamResource(context.getContentResolver().openInputStream(itemImage)) {
                public String getFilename() throws IllegalStateException {
                    return fileInfo.getFileName();

                public long contentLength() throws IOException {
                    return fileInfo.getFileSizeInBytes();

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