--HTTP has provisions for several mechanisms for "content negotiation" -- the process of selecting the best representation for a given response when there are multiple representations available. -- RFC 2616, Fielding et al.
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--HTTP has provisions for several mechanisms for "content negotiation" -- the process of selecting the best representation for a given response when there are multiple representations available. -- RFC 2616, Fielding et al.
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--Django provides a few classes that help you manage paginated data – that is, data that’s split across several pages, with “Previous/Next” links.
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REST framework includes a PaginationSerializer class that makes it easy to return paginated data in a way that can then be rendered to arbitrary media types.
Let's start by taking a look at an example from the Django documentation.
-from django.core.paginator import Paginator
-objects = ['john', 'paul', 'george', 'ringo']
-paginator = Paginator(objects, 2)
-page = paginator.page(1)
-page.object_list
-# ['john', 'paul']
-At this point we've got a page object. If we wanted to return this page object as a JSON response, we'd need to provide the client with context such as next and previous links, so that it would be able to page through the remaining results.
-from rest_framework.pagination import PaginationSerializer
-serializer = PaginationSerializer(instance=page)
-serializer.data
-# {'count': 4, 'next': '?page=2', 'previous': None, 'results': [u'john', u'paul']}
-The context argument of the PaginationSerializer class may optionally include the request. If the request is included in the context then the next and previous links returned by the serializer will use absolute URLs instead of relative URLs.
request = RequestFactory().get('/foobar')
-serializer = PaginationSerializer(instance=page, context={'request': request})
-serializer.data
-# {'count': 4, 'next': 'http://testserver/foobar?page=2', 'previous': None, 'results': [u'john', u'paul']}
-We could now return that data in a Response object, and it would be rendered into the correct media type.
Our first example worked because we were using primative objects. If we wanted to paginate a queryset or other complex data, we'd need to specify a serializer to use to serialize the result set itself with.
-We can do this using the object_serializer_class attribute on the inner Meta class of the pagination serializer. For example.
class UserSerializer(serializers.ModelSerializer):
- """
- Serializes user querysets.
- """
- class Meta:
- model = User
- fields = ('username', 'email')
-
-class PaginatedUserSerializer(pagination.PaginationSerializer):
- """
- Serializes page objects of user querysets.
- """
- class Meta:
- object_serializer_class = UserSerializer
-
-queryset = User.objects.all()
-paginator = Paginator(queryset, 20)
-page = paginator.page(1)
-serializer = PaginatedUserSerializer(instance=page)
-serializer.data
-# {'count': 1, 'next': None, 'previous': None, 'results': [{'username': u'admin', 'email': u'admin@example.com'}]}
-The generic class based views ListAPIView and ListCreateAPIView provide pagination of the returned querysets by default. You can customise this behaviour by altering the pagination style, by modifying the default number of results, or by turning pagination off completely.
The default pagination style may be set globally, using the PAGINATION_SERIALIZER and PAGINATE_BY settings. For example.
REST_FRAMEWORK = {
- 'PAGINATION_SERIALIZER': (
- 'example_app.pagination.CustomPaginationSerializer',
- ),
- 'PAGINATE_BY': 10
-}
-You can also set the pagination style on a per-view basis, using the ListAPIView generic class-based view.
class PaginatedListView(ListAPIView):
- model = ExampleModel
- pagination_serializer_class = CustomPaginationSerializer
- paginate_by = 10
-Override pagination.BasePaginationSerializer, and set the fields that you want the serializer to return.
For example.
-class CustomPaginationSerializer(pagination.BasePaginationSerializer):
- next = pagination.NextURLField()
- total_results = serializers.Field(source='paginator.count')
-