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"""
The :mod:`response` module provides :class:`Response` and :class:`ImmediateResponse` classes.
`Response` is a subclass of `HttpResponse`, and can be similarly instantiated and returned
from any view. It is a bit smarter than Django's `HttpResponse`, for it renders automatically
its content to a serial format by using a list of :mod:`renderers`.
To determine the content type to which it must render, default behaviour is to use standard
HTTP Accept header content negotiation. But `Response` also supports overriding the content type
by specifying an ``_accept=`` parameter in the URL. Also, `Response` will ignore `Accept` headers
from Internet Explorer user agents and use a sensible browser `Accept` header instead.
`ImmediateResponse` is an exception that inherits from `Response`. It can be used
to abort the request handling (i.e. ``View.get``, ``View.put``, ...),
and immediately returning a response.
"""
from django.template.response import SimpleTemplateResponse
from django.core.handlers.wsgi import STATUS_CODE_TEXT
from djangorestframework.utils.mediatypes import order_by_precedence
from djangorestframework.utils import MSIE_USER_AGENT_REGEX
from djangorestframework import status
__all__ = ('Response', 'ImmediateResponse')
class Response(SimpleTemplateResponse):
"""
An HttpResponse that may include content that hasn't yet been serialized.
Kwargs:
- content(object). The raw content, not yet serialized. This must be simple Python
data that renderers can handle (e.g.: `dict`, `str`, ...)
- renderers(list/tuple). The renderers to use for rendering the response content.
"""
_ACCEPT_QUERY_PARAM = '_accept' # Allow override of Accept header in URL query params
_IGNORE_IE_ACCEPT_HEADER = True
def __init__(self, content=None, status=None, request=None, renderers=None, headers=None):
# First argument taken by `SimpleTemplateResponse.__init__` is template_name,
# which we don't need
super(Response, self).__init__(None, status=status)
# We need to store our content in raw content to avoid overriding HttpResponse's
# `content` property
self.raw_content = content
self.has_content_body = content is not None
self.request = request
self.headers = headers and headers[:] or []
if renderers is not None:
self.renderers = renderers
def render(self):
#TODO: see ImmediateResponse
try:
return super(Response, self).render()
except ImmediateResponse as response:
response.renderers = self.renderers
return response.render()
@property
def rendered_content(self):
"""
The final rendered content. Accessing this attribute triggers the complete rendering cycle :
selecting suitable renderer, setting response's actual content type, rendering data.
"""
renderer, media_type = self._determine_renderer()
# Set the media type of the response
self['Content-Type'] = renderer.media_type
# Render the response content
if self.has_content_body:
return renderer.render(self.raw_content, media_type)
return renderer.render()
@property
def status_text(self):
"""
Returns reason text corresponding to our HTTP response status code.
Provided for convenience.
"""
return STATUS_CODE_TEXT.get(self.status_code, '')
def _determine_accept_list(self):
"""
Returns a list of accepted media types. This list is determined from :
1. overload with `_ACCEPT_QUERY_PARAM`
2. `Accept` header of the request
If those are useless, a default value is returned instead.
"""
request = self.request
if request is None:
return ['*/*']
if self._ACCEPT_QUERY_PARAM and request.GET.get(self._ACCEPT_QUERY_PARAM, None):
# Use _accept parameter override
return [request.GET.get(self._ACCEPT_QUERY_PARAM)]
elif (self._IGNORE_IE_ACCEPT_HEADER and
'HTTP_USER_AGENT' in request.META and
MSIE_USER_AGENT_REGEX.match(request.META['HTTP_USER_AGENT'])):
# Ignore MSIE's broken accept behavior and do something sensible instead
return ['text/html', '*/*']
elif 'HTTP_ACCEPT' in request.META:
# Use standard HTTP Accept negotiation
return [token.strip() for token in request.META['HTTP_ACCEPT'].split(',')]
else:
# No accept header specified
return ['*/*']
def _determine_renderer(self):
"""
Determines the appropriate renderer for the output, given the list of accepted media types,
and the :attr:`renderers` set on this class.
Returns a 2-tuple of `(renderer, media_type)`
See: RFC 2616, Section 14 - http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html
"""
# Check the acceptable media types against each renderer,
# attempting more specific media types first
# NB. The inner loop here isn't as bad as it first looks :)
# Worst case is we're looping over len(accept_list) * len(self.renderers)
for media_type_list in order_by_precedence(self._determine_accept_list()):
for renderer in self.renderers:
for media_type in media_type_list:
if renderer.can_handle_response(media_type):
return renderer, media_type
# No acceptable renderers were found
raise ImmediateResponse({'detail': 'Could not satisfy the client\'s Accept header',
'available_types': self._rendered_media_types},
status=status.HTTP_406_NOT_ACCEPTABLE,
renderers=self.renderers)
def _get_renderers(self):
if hasattr(self, '_renderers'):
return self._renderers
return ()
def _set_renderers(self, value):
self._renderers = value
renderers = property(_get_renderers, _set_renderers)
@property
def _rendered_media_types(self):
"""
Return an list of all the media types that this response can render.
"""
return [renderer.media_type for renderer in self.renderers]
@property
def _rendered_formats(self):
"""
Return a list of all the formats that this response can render.
"""
return [renderer.format for renderer in self.renderers]
@property
def _default_renderer(self):
"""
Return the response's default renderer class.
"""
return self.renderers[0]
class ImmediateResponse(Response, Exception):
"""
A subclass of :class:`Response` used to abort the current request handling.
"""
#TODO: this is just a temporary fix, the whole rendering/support for ImmediateResponse, should be remade : see issue #163
def render(self):
try:
return super(Response, self).render()
except ImmediateResponse as exc:
renderer, media_type = self._determine_renderer()
self.renderers.remove(renderer)
if len(self.renderers) == 0:
raise RuntimeError('Caught an ImmediateResponse while '\
'trying to render an ImmediateResponse')
return self.render()
def __str__(self):
"""
Since this class is also an exception it has to provide a sensible
representation for the cases when it is treated as an exception.
"""
return ('%s must be caught in try/except block, '
'and returned as a normal HttpResponse' % self.__class__.__name__)
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