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"""
Decorators for views based on HTTP headers.
"""
import logging
from calendar import timegm
from functools import wraps
from django.http import (
HttpResponse, HttpResponseNotAllowed, HttpResponseNotModified,
)
from django.middleware.http import ConditionalGetMiddleware
from django.utils.decorators import available_attrs, decorator_from_middleware
from django.utils.http import (
http_date, parse_etags, parse_http_date_safe, quote_etag,
)
conditional_page = decorator_from_middleware(ConditionalGetMiddleware)
logger = logging.getLogger('django.request')
def require_http_methods(request_method_list):
"""
Decorator to make a view only accept particular request methods. Usage::
@require_http_methods(["GET", "POST"])
def my_view(request):
# I can assume now that only GET or POST requests make it this far
# ...
Note that request methods should be in uppercase.
"""
def decorator(func):
@wraps(func, assigned=available_attrs(func))
def inner(request, *args, **kwargs):
if request.method not in request_method_list:
logger.warning('Method Not Allowed (%s): %s', request.method, request.path,
extra={
'status_code': 405,
'request': request
}
)
return HttpResponseNotAllowed(request_method_list)
return func(request, *args, **kwargs)
return inner
return decorator
require_GET = require_http_methods(["GET"])
require_GET.__doc__ = "Decorator to require that a view only accept the GET method."
require_POST = require_http_methods(["POST"])
require_POST.__doc__ = "Decorator to require that a view only accept the POST method."
require_safe = require_http_methods(["GET", "HEAD"])
require_safe.__doc__ = "Decorator to require that a view only accept safe methods: GET and HEAD."
def _precondition_failed(request):
logger.warning('Precondition Failed: %s', request.path,
extra={
'status_code': 412,
'request': request
},
)
return HttpResponse(status=412)
def condition(etag_func=None, last_modified_func=None):
"""
Decorator to support conditional retrieval (or change) for a view
function.
The parameters are callables to compute the ETag and last modified time for
the requested resource, respectively. The callables are passed the same
parameters as the view itself. The Etag function should return a string (or
None if the resource doesn't exist), whilst the last_modified function
should return a datetime object (or None if the resource doesn't exist).
If both parameters are provided, all the preconditions must be met before
the view is processed.
This decorator will either pass control to the wrapped view function or
return an HTTP 304 response (unmodified) or 412 response (preconditions
failed), depending upon the request method.
Any behavior marked as "undefined" in the HTTP spec (e.g. If-none-match
plus If-modified-since headers) will result in the view function being
called.
"""
def decorator(func):
@wraps(func, assigned=available_attrs(func))
def inner(request, *args, **kwargs):
# Get HTTP request headers
if_modified_since = request.META.get("HTTP_IF_MODIFIED_SINCE")
if if_modified_since:
if_modified_since = parse_http_date_safe(if_modified_since)
if_unmodified_since = request.META.get("HTTP_IF_UNMODIFIED_SINCE")
if if_unmodified_since:
if_unmodified_since = parse_http_date_safe(if_unmodified_since)
if_none_match = request.META.get("HTTP_IF_NONE_MATCH")
if_match = request.META.get("HTTP_IF_MATCH")
etags = []
if if_none_match or if_match:
# There can be more than one ETag in the request, so we
# consider the list of values.
try:
etags = parse_etags(if_none_match or if_match)
except ValueError:
# In case of invalid etag ignore all ETag headers.
# Apparently Opera sends invalidly quoted headers at times
# (we should be returning a 400 response, but that's a
# little extreme) -- this is Django bug #10681.
if_none_match = None
if_match = None
# Compute values (if any) for the requested resource.
def get_last_modified():
if last_modified_func:
dt = last_modified_func(request, *args, **kwargs)
if dt:
return timegm(dt.utctimetuple())
res_etag = etag_func(request, *args, **kwargs) if etag_func else None
res_last_modified = get_last_modified()
response = None
if not ((if_match and if_modified_since) or
(if_none_match and if_unmodified_since) or
(if_modified_since and if_unmodified_since) or
(if_match and if_none_match)):
# We only get here if no undefined combinations of headers are
# specified.
if ((if_none_match and (res_etag in etags or
"*" in etags and res_etag)) and
(not if_modified_since or
(res_last_modified and if_modified_since and
res_last_modified <= if_modified_since))):
if request.method in ("GET", "HEAD"):
response = HttpResponseNotModified()
else:
response = _precondition_failed(request)
elif (if_match and ((not res_etag and "*" in etags) or
(res_etag and res_etag not in etags) or
(res_last_modified and if_unmodified_since and
res_last_modified > if_unmodified_since))):
response = _precondition_failed(request)
elif (not if_none_match and request.method in ("GET", "HEAD") and
res_last_modified and if_modified_since and
res_last_modified <= if_modified_since):
response = HttpResponseNotModified()
elif (not if_match and
res_last_modified and if_unmodified_since and
res_last_modified > if_unmodified_since):
response = _precondition_failed(request)
if response is None:
response = func(request, *args, **kwargs)
# Set relevant headers on the response if they don't already exist.
if res_last_modified and not response.has_header('Last-Modified'):
response['Last-Modified'] = http_date(res_last_modified)
if res_etag and not response.has_header('ETag'):
response['ETag'] = quote_etag(res_etag)
return response
return inner
return decorator
# Shortcut decorators for common cases based on ETag or Last-Modified only
def etag(etag_func):
return condition(etag_func=etag_func)
def last_modified(last_modified_func):
return condition(last_modified_func=last_modified_func)
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