98 lines
3.9 KiB
Python
98 lines
3.9 KiB
Python
"""
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Content negotiation deals with selecting an appropriate renderer given the
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incoming request. Typically this will be based on the request's Accept header.
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"""
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from django.http import Http404
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from rest_framework import exceptions
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from rest_framework.settings import api_settings
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from rest_framework.utils.mediatypes import (
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_MediaType, media_type_matches, order_by_precedence
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)
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class BaseContentNegotiation:
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def select_parser(self, request, parsers):
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raise NotImplementedError('.select_parser() must be implemented')
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def select_renderer(self, request, renderers, format_suffix=None):
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raise NotImplementedError('.select_renderer() must be implemented')
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class DefaultContentNegotiation(BaseContentNegotiation):
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settings = api_settings
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def select_parser(self, request, parsers):
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"""
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Given a list of parsers and a media type, return the appropriate
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parser to handle the incoming request.
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"""
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for parser in parsers:
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if media_type_matches(parser.media_type, request.content_type):
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return parser
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return None
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def select_renderer(self, request, renderers, format_suffix=None):
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"""
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Given a request and a list of renderers, return a two-tuple of:
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(renderer, media type).
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"""
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# Allow URL style format override. eg. "?format=json
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format_query_param = self.settings.URL_FORMAT_OVERRIDE
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format = format_suffix or request.query_params.get(format_query_param)
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if format:
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renderers = self.filter_renderers(renderers, format)
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accepts = self.get_accept_list(request)
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# Check the acceptable media types against each renderer,
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# attempting more specific media types first
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# NB. The inner loop here isn't as bad as it first looks :)
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# Worst case is we're looping over len(accept_list) * len(self.renderers)
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for media_type_set in order_by_precedence(accepts):
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for renderer in renderers:
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for media_type in media_type_set:
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if media_type_matches(renderer.media_type, media_type):
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# Return the most specific media type as accepted.
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media_type_wrapper = _MediaType(media_type)
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if (
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_MediaType(renderer.media_type).precedence >
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media_type_wrapper.precedence
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):
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# Eg client requests '*/*'
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# Accepted media type is 'application/json'
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full_media_type = ';'.join(
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(renderer.media_type,) +
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tuple(
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'{}={}'.format(key, value)
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for key, value in media_type_wrapper.params.items()
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)
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)
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return renderer, full_media_type
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else:
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# Eg client requests 'application/json; indent=8'
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# Accepted media type is 'application/json; indent=8'
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return renderer, media_type
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raise exceptions.NotAcceptable(available_renderers=renderers)
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def filter_renderers(self, renderers, format):
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"""
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If there is a '.json' style format suffix, filter the renderers
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so that we only negotiation against those that accept that format.
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"""
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renderers = [renderer for renderer in renderers
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if renderer.format == format]
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if not renderers:
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raise Http404
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return renderers
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def get_accept_list(self, request):
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"""
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Given the incoming request, return a tokenized list of media
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type strings.
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"""
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header = request.META.get('HTTP_ACCEPT', '*/*')
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return [token.strip() for token in header.split(',')]
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