def checkPreconditions(self, request):
"""
Checks all preconditions imposed by this resource upon a request made
against it.
@param request: the request to process.
@raise http.HTTPError: if any precondition fails.
@return: C{None} or a deferred whose callback value is C{request}.
"""
#
# http.checkPreconditions() gets called by the server after every
# GET or HEAD request.
#
# For other methods, we need to know to bail out before request
# processing, especially for methods that modify server state (eg. PUT).
# We also would like to do so even for methods that don't, if those
# methods might be expensive to process. We're assuming that GET and
# HEAD are not expensive.
#
if request.method not in ("GET", "HEAD"):
http.checkPreconditions(request)
# Check per-method preconditions
method = getattr(self, "preconditions_" + request.method, None)
if method:
return method(request)
def checkPreconditions(self, request):
# This code replaces the code in resource.RenderMixin
if request.method not in ("GET", "HEAD"):
http.checkPreconditions(
request,
entityExists = self.exists(),
etag = self.etag(),
lastModified = self.lastModified(),
)
# Check per-method preconditions
method = getattr(self, "preconditions_" + request.method, None)
if method:
return method(request)
def preconditionfilter(request, response):
if request.method in ("GET", "HEAD"):
http.checkPreconditions(request, response)
return response