我有两个Django模型,一个用于http://example.com等开始网址,另一个用于网页链接,例如http://example.com/website1,http://example.com/website2等.所有抓取的Web链接都是start_urls列表中某个起始URL的子网站.
Web链接模型与起始URL模型具有多对一关系,即Web链接模型具有到开始URL模型的外键.为了将我的已删除的Web链接正确保存到数据库,我需要告诉CrawlSpider的parse_item()方法,该方法启动了已删除的Web链接所属的URL.我怎样才能做到这一点？ Scrapy的DjangoItem类在这方面没有帮助,因为我仍然必须明确定义使用的启动URL.
换句话说,如何将当前使用的起始URL传递给parse_item()方法,以便我可以将它与适当的刮取Web链接一起保存到数据库中？有任何想法吗？提前致谢！
解决方法
但是你可以覆盖make_requests_from_url方法并将开始网址放入meta.然后在解析中你可以从那里提取它(如果你在后面的请求中产生了解析方法,不要忘记在它们中转发那个开始网址).
我没有使用CrawlSpider,也许Maxim建议你可以使用它,但请记住,response.url在可能的重定向后有url.
这是我将如何做的一个例子,但它只是一个例子(取自scrapy教程)并且未经过测试：
class MySpider(CrawlSpider):
name = 'example.com'
allowed_domains = ['example.com']
start_urls = ['http://www.example.com']
rules = (
# Extract links matching 'category.PHP' (but not matching 'subsection.PHP')
# and follow links from them (since no callback means follow=True by default).
Rule(SgmlLinkExtractor(allow=('category\.PHP',),deny=('subsection\.PHP',))),# Extract links matching 'item.PHP' and parse them with the spider's method parse_item
Rule(SgmlLinkExtractor(allow=('item\.PHP',)),callback='parse_item'),)
def parse(self,response): # When writing crawl spider rules,avoid using parse as callback,since the CrawlSpider uses the parse method itself to implement its logic. So if you override the parse method,the crawl spider will no longer work.
for request_or_item in CrawlSpider.parse(self,response):
if isinstance(request_or_item,Request):
request_or_item = request_or_item.replace(Meta = {'start_url': response.Meta['start_url']})
yield request_or_item
def make_requests_from_url(self,url):
"""A method that receives a URL and returns a Request object (or a list of Request objects) to scrape.
This method is used to construct the initial requests in the start_requests() method,and is typically used to convert urls to requests.
"""
return Request(url,dont_filter=True,Meta = {'start_url': url})
def parse_item(self,response):
self.log('Hi,this is an item page! %s' % response.url)
hxs = HtmlXPathSelector(response)
item = Item()
item['id'] = hxs.select('//td[@id="item_id"]/text()').re(r'ID: (\d+)')
item['name'] = hxs.select('//td[@id="item_name"]/text()').extract()
item['description'] = hxs.select('//td[@id="item_description"]/text()').extract()
item['start_url'] = response.Meta['start_url']
return item
问你是否有任何问题.顺便说一句,使用PyDev的“转到定义”功能,您可以看到scrapy源并了解Request,make_requests_from_url和其他类和方法所期望的参数.进入代码可以帮助并节省您的时间,尽管一开始可能看起来很困难.