1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
|
"""
Downloader Middleware manager
See documentation in docs/topics/downloader-middleware.rst
"""
import six
from twisted.internet import defer
from scrapy.http import Request, Response
from scrapy.middleware import MiddlewareManager
from scrapy.utils.defer import mustbe_deferred
from scrapy.utils.conf import build_component_list
class DownloaderMiddlewareManager(MiddlewareManager):
component_name = 'downloader middleware'
@classmethod
def _get_mwlist_from_settings(cls, settings):
return build_component_list(
settings.getwithbase('DOWNLOADER_MIDDLEWARES'))
def _add_middleware(self, mw):
if hasattr(mw, 'process_request'):
self.methods['process_request'].append(mw.process_request)
if hasattr(mw, 'process_response'):
self.methods['process_response'].insert(0, mw.process_response)
if hasattr(mw, 'process_exception'):
self.methods['process_exception'].insert(0, mw.process_exception)
def download(self, download_func, request, spider):
@defer.inlineCallbacks
def process_request(request):
for method in self.methods['process_request']:
response = yield method(request=request, spider=spider)
assert response is None or isinstance(response, (Response, Request)), \
'Middleware %s.process_request must return None, Response or Request, got %s' % \
(six.get_method_self(method).__class__.__name__, response.__class__.__name__)
if response:
defer.returnValue(response)
defer.returnValue((yield download_func(request=request,spider=spider)))
@defer.inlineCallbacks
def process_response(response):
assert response is not None, 'Received None in process_response'
if isinstance(response, Request):
defer.returnValue(response)
for method in self.methods['process_response']:
response = yield method(request=request, response=response,
spider=spider)
assert isinstance(response, (Response, Request)), \
'Middleware %s.process_response must return Response or Request, got %s' % \
(six.get_method_self(method).__class__.__name__, type(response))
if isinstance(response, Request):
defer.returnValue(response)
defer.returnValue(response)
@defer.inlineCallbacks
def process_exception(_failure):
exception = _failure.value
for method in self.methods['process_exception']:
response = yield method(request=request, exception=exception,
spider=spider)
assert response is None or isinstance(response, (Response, Request)), \
'Middleware %s.process_exception must return None, Response or Request, got %s' % \
(six.get_method_self(method).__class__.__name__, type(response))
if response:
defer.returnValue(response)
defer.returnValue(_failure)
deferred = mustbe_deferred(process_request, request)
deferred.addErrback(process_exception)
deferred.addCallback(process_response)
return deferred
|
