What are the parsers used for in the Django Rest Framework?

Question

I have a simple file model

class Documents(models.Model):
    """ uploaded documents"""

    author = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
    upload = models.FileField(storage=PrivateMediaStorage())
    filename = models.CharField(_('documents name'), max_length=255, blank=True, null=True)
    datafile = models.FileField()
    created = models.DateTimeField(auto_now_add=True)
    type = models.ForeignKey(Doctype, on_delete=models.CASCADE, blank=True)

To display the list of uploaded documents and add new files, I use the class

class DocumentsListView(viewsets.ViewSetMixin,generics.ListCreateAPIView):
    queryset = Documents.objects.all()
    serializer_class = DocumentsSerializer

    def perform_create(self, serializer):
        serializer.save(author=self.request.user)

serializer.py

class DocumentsSerializer(AwsUrlMixin, serializers.ModelSerializer):
    type_name = serializers.CharField(source='type.type', read_only=True)
    type = serializers.PrimaryKeyRelatedField(queryset=Doctype.objects.all())
    view_file = serializers.SerializerMethodField()
    author = serializers.CharField(source='author.username', read_only=True)
    created = serializers.DateTimeField(format=date_format, input_formats=None, default_timezone=None, read_only=True)

    class Meta:
        model = Documents
        fields = ('id', 'author', 'filename', 'datafile', 'type', 'type_name', 'created', 'view_file')

I use the standard DRF interface and I display everything normally and add new files to the database.

While reading the documentation I came across parsers such as MultipartParser, FileUploadParser, which are also used when adding new files. I can't underatand when to use them and what function they perform, because now everything works without them.

The documentation hasn't given me a clear understanding of when I need to use parsers.

I try to add

parser_classes = (MultiPartParser, FileUploadParser)

to views.py and nothing change. Everything works as it did before. I'd appreciate it if you'd make that clear to me.

Have your read this? If so, you'll see that parsers are set globally or can be overridden in views (not in serialisers). They basically make sure that the request body received by the view is parsed and transformed into a python object (a dict usually) that can be handled by the serialisers and vice versa. Please let us know what part of this document specifically you don't understand. — dirkgroten
@dirkgroten I made a mistake writing that I add parser_classes to the serializer, of course in views. It's not clear to me if everything works without parsers, why do I need them and when do I have to add them to views, and when can I do without them?What changed after adding parser to view? — Jekson

anjaneyulubatta505 anjaneyulubatta505 · Accepted Answer · 2019-08-28T10:22:29

Parsers in Django REST are used to parse the content of incoming HTTP request. In HTTP request we receive the data as a string format. Parsers will parse the HTTP contents in to python data types based on the Content-Type header received in the HTTP request. Django REST Framework provides a number of built-in parsers which parses different types of contents like application/json, multipart/form-data, application/xml, etc., based on the Content-Type header received in the HTTP request.

Parser Classes in Django REST:

JSONParser
- It parses the incoming request JSON content into python content type dict.
- It is used if "Content-Type" is set to "application/json".
FormParser
- It parses the incoming request form contents into QueryDict.
- It is used if "Content-Type" is set to "application/x-www-form-urlencoded".
MultiPartParser
- It parses the incoming request form contents into QueryDict.
- It is used if "Content-Type" is set to "multipart/form-data".
- request.data will be a QueryDict containing all the form parameters.
- request.files will be a QueryDict containing all the form files.
- FormParser and MultiPartParser together used for full support of HTML form data.
FileUploadParser
- It is used to parse a single file sent in HTTP request.
- It expects a url keyword argument "filename". If it's not provided then we should provide the filename in the Content-Disposition HTTP header. For example Content-Disposition: attachment; filename=upload.jpg.
- request.file is used to access the contents of uploaded file.

Reference: https://learnbatta.com/blog/parsers-in-django-rest-framework-85/

What are the parsers used for in the Django Rest Framework?

2 Answers