Source code for scrapy.downloadermiddlewares.ajaxcrawl

import re
import logging

from w3lib import html

from scrapy.exceptions import NotConfigured
from scrapy.http import HtmlResponse

logger = logging.getLogger(__name__)

[docs]class AjaxCrawlMiddleware: """ Handle 'AJAX crawlable' pages marked as crawlable via meta tag. For more info see """ def __init__(self, settings): if not settings.getbool('AJAXCRAWL_ENABLED'): raise NotConfigured # XXX: Google parses at least first 100k bytes; scrapy's redirect # middleware parses first 4k. 4k turns out to be insufficient # for this middleware, and parsing 100k could be slow. # We use something in between (32K) by default. self.lookup_bytes = settings.getint('AJAXCRAWL_MAXSIZE', 32768) @classmethod def from_crawler(cls, crawler): return cls(crawler.settings) def process_response(self, request, response, spider): if not isinstance(response, HtmlResponse) or response.status != 200: return response if request.method != 'GET': # other HTTP methods are either not safe or don't have a body return response if 'ajax_crawlable' in request.meta: # prevent loops return response if not self._has_ajax_crawlable_variant(response): return response # scrapy already handles #! links properly ajax_crawl_request = request.replace(url=request.url + '#!') logger.debug("Downloading AJAX crawlable %(ajax_crawl_request)s instead of %(request)s", {'ajax_crawl_request': ajax_crawl_request, 'request': request}, extra={'spider': spider}) ajax_crawl_request.meta['ajax_crawlable'] = True return ajax_crawl_request def _has_ajax_crawlable_variant(self, response): """ Return True if a page without hash fragment could be "AJAX crawlable" according to """ body = response.text[:self.lookup_bytes] return _has_ajaxcrawlable_meta(body)
# XXX: move it to w3lib? _ajax_crawlable_re = re.compile(r'<meta\s+name=["\']fragment["\']\s+content=["\']!["\']/?>') def _has_ajaxcrawlable_meta(text): """ >>> _has_ajaxcrawlable_meta('<html><head><meta name="fragment" content="!"/></head><body></body></html>') True >>> _has_ajaxcrawlable_meta("<html><head><meta name='fragment' content='!'></head></html>") True >>> _has_ajaxcrawlable_meta('<html><head><!--<meta name="fragment" content="!"/>--></head><body></body></html>') False >>> _has_ajaxcrawlable_meta('<html></html>') False """ # Stripping scripts and comments is slow (about 20x slower than # just checking if a string is in text); this is a quick fail-fast # path that should work for most pages. if 'fragment' not in text: return False if 'content' not in text: return False text = html.remove_tags_with_content(text, ('script', 'noscript')) text = html.replace_entities(text) text = html.remove_comments(text) return is not None