I want to send an Article from and Android client to a REST server. Here is the Python model from the server:
class Article(models.Model):
author = models.CharField(max_length=256, blank=False)
photo = models.ImageField()
The following interface describes the former implementation:
@POST("/api/v1/articles/")
public Observable<CreateArticleResponse> createArticle(
@Body Article article
);
Now I want to send an image with the Article data. The photo
is not part of the Article model on the Android client.
@Multipart
@POST("/api/v1/articles/")
public Observable<CreateArticleResponse> createArticle(
@Part("article") Article article,
@Part("photo") TypedFile photo
);
The API is prepared and successfully tested with cURL.
$ curl -vX POST http://localhost:8000/api/v1/articles/ \
-H "Content-Type: multipart/form-data" \
-H "Accept:application/json" \
-F "author=cURL" \
-F "photo=@/home/user/Desktop/article-photo.png"
When I send data through createArticle()
from the Android client I receive an HTTP 400
status stating that the fields are required/missing.
D <--- HTTP 400 http://192.168.1.1/articles/ (2670ms)
D Date: Mon, 20 Apr 2015 12:00:00 GMT
D Server: WSGIServer/0.1 Python/2.7.8
D Vary: Accept, Cookie
D X-Frame-Options: SAMEORIGIN
D Content-Type: application/json
D Allow: GET, POST, HEAD, OPTIONS
D OkHttp-Selected-Protocol: http/1.0
D OkHttp-Sent-Millis: 1429545450469
D OkHttp-Received-Millis: 1429545453120
D {"author":["This field is required."],"photo":["No file was submitted."]}
D <--- END HTTP (166-byte body)
E 400 BAD REQUEST
This is what is received as request.data
on the server side:
ipdb> print request.data
<QueryDict: {u'article': [u'{"author":"me"}'], \
u'photo': [<TemporaryUploadedFile: IMG_1759215522.jpg \
(multipart/form-data)>]}>
How can convert the Article object in a multipart conform data type? I read that Retrofit might allow to use Converters for this. It should be something that implements a retrofit.mime.TypedOutput
as far as I understood for the documentation.
Multipart parts use the
RestAdapter
's converter or they can implementTypedOutput
to handle their own serialization.
According to your curl request you are trying to create smth like this:
POST http://localhost:8000/api/v1/articles/ HTTP/1.1
User-Agent: curl/7.30.0
Host: localhost
Connection: Keep-Alive
Accept: application/json
Content-Length: 183431
Expect: 100-continue
Content-Type: multipart/form-data; boundary=----------------------------23473c7acabb
------------------------------23473c7acabb
Content-Disposition: form-data; name="author"
cURL
------------------------------23473c7acabb
Content-Disposition: form-data; name="photo"; filename="article-photo.png"
Content-Type: application/octet-stream
‰PNG
<!RAW BYTES HERE!>
M\UUÕ+4qUUU¯°WUUU¿×ß¿þ Naa…k¿ IEND®B`‚
------------------------------23473c7acabb--
With retrofit adapter this request can be created in a next way:
@Multipart
@POST("/api/v1/articles/")
Observable<Response> uploadFile(@Part("author") TypedString authorString,
@Part("photo") TypedFile photoFile);
Usage:
TypedString author = new TypedString("cURL");
File photoFile = new File("/home/user/Desktop/article-photo.png");
TypedFile photoTypedFile = new TypedFile("image/*", photoFile);
retrofitAdapter.uploadFile(author, photoTypedFile)
.subscribe(<...>);
Which creates similar output:
POST http://localhost:8000/api/v1/articles/ HTTP/1.1
Content-Type: multipart/form-data; boundary=32230279-83af-4480-abfc-88a880b21b19
Content-Length: 709
Host: localhost
Connection: Keep-Alive
Accept-Encoding: gzip
User-Agent: okhttp/2.3.0
--32230279-83af-4480-abfc-88a880b21b19
Content-Disposition: form-data; name="author"
Content-Type: text/plain; charset=UTF-8
Content-Length: 4
Content-Transfer-Encoding: binary
cUrl
--32230279-83af-4480-abfc-88a880b21b19
Content-Disposition: form-data; name="photo"; filename="article-photo.png"
Content-Type: image/*
Content-Length: 254
Content-Transfer-Encoding: binary
<!RAW BYTES HERE!>
--32230279-83af-4480-abfc-88a880b21b19--
The key difference here is that you used POJO Article article
as multipart param, which by default is converted by Converter
into json. And your server expects plain string instead. With curl you are sending cURL
, not {"author":"cURL"}
.