Question

194

Getting '400 Bad Request' when using multipart/form-data as Content-Type in XHR

rated 0 times [ 200] [ 6] / answers: 1 / hits: 34516 / 14 Years ago, sun, january 23, 2011, 12:00:00

I have an AJAX request that sends out some data. The data respects the multipart/form-data specification.

The problem I'm facing is that the browser sets the Content-Type header to text/plain and it should be multipart/form-data.

I've tried doing this: request.setRequestHeader(Content-Type, multipart/form-data); but this gives out an 400 Bad Request error.

If I do request.setRequestHeader(Content-Typexxxx, multipart/form-data); there is no error, the Content-Typexxxx header is set but it obviously is no help to me.

I guess there is a list of valid Content-Type headers one can set and multipart/form-data isn't among them, but I cannot find a sollution to my predicament.

Sample of the data actually being sent:

Content-Type: multipart/form-data; boundary=l3iPy71otz



--l3iPy71otz

Content-Disposition: form-data; name=titluPublic



Variation_1

--l3iPy71otz

Content-Disposition: form-data; name=nr_versiune





--l3iPy71otz--

Thanks!

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answered 14 Years ago dominiqued · Accepted Answer

You didn't set the boundary in your request header, as in:

request.setRequestHeader(Content-Type, multipart/form-data; boundary=l3iPy71otz);

For more information, see RFC 2045:

5 Content-Type Header Field
[…]

Parameters are modifiers of the media
subtype, and as such do not
fundamentally affect the nature of the
content. The set of meaningful
parameters depends on the media type
and subtype. Most parameters are
associated with a single specific
subtype. However, a given
top-level media type may define
parameters which are applicable to
any subtype of that type. Parameters
may be required by their defining
content type or subtype or they may be
optional. MIME implementations must
ignore any parameters whose names they
do not recognize.

For example, the charset
parameter is applicable to any subtype
of text, while the boundary
parameter is required for any subtype
of the multipart media type.

Update: Another problem I found on the net appears when a charset is added to the Content-type in the request header, but not in the message boundaries in the body (this is also true for your test case). It doesn't seem a likely solution, but perhaps it helps.

In your case, explicitly add a charset to both the request header and in the message boundaries:

data.params += -- + data.uniqid + ; charset=UTF-8 + data.crlf;

…

request.setRequestHeader(Content-Type, multipart/form-data; boundary= + data.uniqid + ; charset=UTF-8);

Update 2: After trying this myself locally, I noticed the leading boundary wasn't recognized as such, but interpreted as the last parameter contents (on my more forgiving server). Perhaps that was causing Apache to throw a 400 Bad Request error.

After some trial and error, I noticed that that was caused because the server expected the charset to be in every boundary, even the last one. To prevent confusion, I decided to explicitly set the charset in the request header before the boundary parameter, so that the boundary would be the last parameter in the Content-type request header. After this, everything seemed to work fine.

data.params = Content-Type: multipart/form-data; boundary= + data.uniqid;

…

data.params += -- + data.uniqid + data.crlf;

…

data.params += -- + data.uniqid + --;

…

request.setRequestHeader(Content-Type, multipart/form-data; charset=UTF-8; boundary= + data.uniqid);