Exception: You cannot access body after reading from request's data stream

Question

Since Django 1.5 raw post data is accessible via request.body.

In my application I sometimes get data send via a form and sometimes raw data (json for example). Is there any way to write a function like this that does not fail?

def get_post_var(request, name):
    result = request.POST.get(name)
    if result:
        return result

    post_body = dict(urlparse.parse_qsl(request.body))
    result = post_body.get(name)
    if result:
        return result

    return None

Antlion

What do you mean by "sometimes plain data". If its a POST request, django will take care of populating request.POST, irrespective of whether the data is submitted via a form or through curl or anything else. – Woozy

I mean non-form data (json for example) as described here: docs.djangoproject.com/en/1.5/ref/request-response/… – Antlion

Answer 1

Use request.data instead of request.body.

request.data does not read the data stream again.

Lambrequin

This is the actual answer that fixes the error. Should have higher upvotes. – Teagan

I get AttributeError: 'WSGIRequest' object has no attribute 'data' in Django 1.4 using request.data. Some idea about how can I resolve that? – Quaky

@CarMoreno @Ulvi I believe request.data is a DRF thing. The request object that is passed to DRF views, is different to the request object passed to normal django views. – Gazebo

@TimHong this fixes the problem when the problem is caused by DRF, but 1) this is not always the case, 2) it's not explained in the answer and confuses people, 3) nowhere in the question it's mentioned DRF. Sure, probably 90% of the time this is caused by DRF, but Adam's answer is the most general and correct explanation which applies in any case. – Yanyanaton

WSGIRequest object has no attribute data with django 4. – Taster

What if I need the raw response body? I don't want it parsed. – Ga

Answer 2

The error You cannot access body after reading from request's data stream will be triggered on a request if (1) that request method is POST, (2) that request's POST dictionary is accessed in middleware, in either process_request or process_view and (3) within the view function, request.body is accessed. It is on (3) that the error will be raised, even though the real cause of the bug is (2).

In order to resolve the error, you need to examine your middleware for where it accesses request.POST and modify it such that it doesn't access request.POST anymore.

The Django docs say that middleware should not access request.POST, and this is one consequence of ignoring that recommendation.

Also check out this Django ticket on the issue, which includes the note:

[M]iddleware that hits request.POST should (usually) be considered a bug. It means that the view will be unable to set any custom upload handlers, perform custom parsing of the request body, or enforce permission checks prior to file uploads being accepted.

Capture

It should be added that this applies not just to request.POST, but also to request.body. – Malissamalissia

I actually need to access request.data how do I do that? – Alissaalistair

I get request has no attribute data if I use request.data – Alissaalistair

Answer 3

Adding to Adam Easterling's answer it is worth noting that Django itself 'violates' the hint of not using request.POST in middleware:

The CsrfViewMiddleware class can be considered an exception, as it provides the csrf_exempt() and csrf_protect() decorators which allow views to explicitly control at what point the CSRF validation should occur.

Which does not sanitilize the violation IMO

Lombard

Indeed this was an annoyance for me. The solution/workaround is to use PUT rather than POST if you mean to read request body (other than through the POST/FILES). – Istanbul

Answer 4

For those interested to know, I faced this issue:

You cannot access body after reading from request's data stream

when I added 'oauth2_provider.contrib.rest_framework.OAuth2Authentication' in the "REST_FRAMEWORK" like so in the settings.py:

REST_FRAMEWORK = {
   ...
    'DEFAULT_AUTHENTICATION_CLASSES': (
      ...
       'oauth2_provider.contrib.rest_framework.OAuth2Authentication',
      ...
    ),

Of course disabling this will work but not a workaround I would be proud of.

Earnest

You must explicitly use authentication_classes = [] at the top of your APIView to solve this issue – Tynishatynwald

Answer 5

I was able to read my request.POST after putting @csrf_exempt before my view function. Because CSRF middleware accesses POST data.

Reception

Answer 6

You need call request.data instead request.body, if there's still an error, you need to call request.data ONLY one time (check you view, middleware, or maybe paginator) and if you find that you call it more then one time, add request.data to reference, for example request_data, or smth like this. It's work for me

Rsfsr

Answer 7

For those with the same error who are not readying the body or POST, I had this same error when I used this line of code in a process_view middleware::

   event = request.event if 'event' in request else None

Solved by settings request.event = None at the top of the function so I could then use:

    event = request.event

Charlacharlady