Source code for django.middleware.http

from django.utils.cache import (
    cc_delim_re, get_conditional_response, set_response_etag,
from django.utils.deprecation import MiddlewareMixin
from django.utils.http import parse_http_date_safe

[docs]class ConditionalGetMiddleware(MiddlewareMixin): """ Handles conditional GET operations. If the response has an ETag or Last-Modified header, and the request has If-None-Match or If-Modified-Since, the response is replaced by an HttpNotModified. An ETag header is added if needed. """ def process_response(self, request, response): # It's too late to prevent an unsafe request with a 412 response, and # for a HEAD request, the response body is always empty so computing # an accurate ETag isn't possible. if request.method != 'GET': return response if self.needs_etag(response) and not response.has_header('ETag'): set_response_etag(response) etag = response.get('ETag') last_modified = response.get('Last-Modified') if last_modified: last_modified = parse_http_date_safe(last_modified) if etag or last_modified: return get_conditional_response( request, etag=etag, last_modified=last_modified, response=response, ) return response def needs_etag(self, response): """ Return True if an ETag header should be added to response. """ cache_control_headers = cc_delim_re.split(response.get('Cache-Control', '')) return all(header.lower() != 'no-store' for header in cache_control_headers)
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