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- from collections import defaultdict, deque
- import logging
- import pprint
- from scrapy.exceptions import NotConfigured
- from scrapy.utils.misc import create_instance, load_object
- from scrapy.utils.defer import process_parallel, process_chain, process_chain_both
- logger = logging.getLogger(__name__)
- class MiddlewareManager(object):
- """Base class for implementing middleware managers"""
- component_name = 'foo middleware'
- def __init__(self, *middlewares):
- self.middlewares = middlewares
- self.methods = defaultdict(deque)
- for mw in middlewares:
- self._add_middleware(mw)
- @classmethod
- def _get_mwlist_from_settings(cls, settings):
- raise NotImplementedError
- @classmethod
- def from_settings(cls, settings, crawler=None):
- mwlist = cls._get_mwlist_from_settings(settings)
- middlewares = []
- enabled = []
- for clspath in mwlist:
- try:
- mwcls = load_object(clspath)
- mw = create_instance(mwcls, settings, crawler)
- middlewares.append(mw)
- enabled.append(clspath)
- except NotConfigured as e:
- if e.args:
- clsname = clspath.split('.')[-1]
- logger.warning("Disabled %(clsname)s: %(eargs)s",
- {'clsname': clsname, 'eargs': e.args[0]},
- extra={'crawler': crawler})
- logger.info("Enabled %(componentname)ss:\n%(enabledlist)s",
- {'componentname': cls.component_name,
- 'enabledlist': pprint.pformat(enabled)},
- extra={'crawler': crawler})
- return cls(*middlewares)
- @classmethod
- def from_crawler(cls, crawler):
- return cls.from_settings(crawler.settings, crawler)
- def _add_middleware(self, mw):
- if hasattr(mw, 'open_spider'):
- self.methods['open_spider'].append(mw.open_spider)
- if hasattr(mw, 'close_spider'):
- self.methods['close_spider'].appendleft(mw.close_spider)
- def _process_parallel(self, methodname, obj, *args):
- return process_parallel(self.methods[methodname], obj, *args)
- def _process_chain(self, methodname, obj, *args):
- return process_chain(self.methods[methodname], obj, *args)
- def _process_chain_both(self, cb_methodname, eb_methodname, obj, *args):
- return process_chain_both(self.methods[cb_methodname], \
- self.methods[eb_methodname], obj, *args)
- def open_spider(self, spider):
- return self._process_parallel('open_spider', spider)
- def close_spider(self, spider):
- return self._process_parallel('close_spider', spider)
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