scrapy中的下载中间件及UA池和代理池
阅读目录
下载中间件
下载中间件（Downloader Middlewares） 位于scrapy引擎和下载器之间的一层组件。
- 作用：
（1）引擎将请求传递给下载器过程中， 下载中间件可以对请求进行一系列处理。比如设置请求的 User-Agent，设置代理等
（2）在下载器完成将Response传递给引擎中，下载中间件可以对响应进行一系列处理。比如进行gzip解压等。
我们主要使用下载中间件处理请求，一般会对请求设置随机的User-Agent ，设置随机的代理。目的在于防止爬取网站的反爬虫策略。
UA池：User-Agent池
- 作用：尽可能多的将scrapy工程中的请求伪装成不同类型的浏览器身份。
- 操作流程：
1.在下载中间件中拦截请求
2.将拦截到的请求的请求头信息中的UA进行篡改伪装
3.在配置文件中开启下载中间件
见下面示例代码
IP代理池
- 作用：尽可能多的将scrapy工程中的请求的IP设置成不同的。
- 操作流程：
1.在下载中间件中拦截请求
2.将拦截到的请求的IP修改成某一代理IP
3.在配置文件中开启下载中间件
注意：将异常的请求拦截到之后，通过代理IP相关的操作，就可以将改异常的请求变成非异常的请求，然后必须重新对该请求进行重新的请求发送：return request 即可
见下面示例代码
针对上面UA代理池IP代理池进行下面的示例：
爬虫文件：
# -*- coding: utf-8 -*- import scrapy class MiddleSpider(scrapy.Spider): name = 'middle' # allowed_domains = ['www.xxx.com'] start_urls = ['https://www.baidu.com/s?wd=ip'] def parse(self, response): page_text = response.text
中间件：
# -*- coding: utf-8 -*- # Define here the models for your spider middleware # # See documentation in: # https://doc.scrapy.org/en/latest/topics/spider-middleware.html from scrapy import signals import random class MiddleproDownloaderMiddleware(object): # Not all methods need to be defined. If a method is not defined, # scrapy acts as if the downloader middleware does not modify the # passed objects. user_agent_list = [ "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.1 " "(KHTML, like Gecko) Chrome/22.0.1207.1 Safari/537.1", "Mozilla/5.0 (X11; CrOS i686 2268.111.0) AppleWebKit/536.11 " "(KHTML, like Gecko) Chrome/20.0.1132.57 Safari/536.11", "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.6 " "(KHTML, like Gecko) Chrome/20.0.1092.0 Safari/536.6", "Mozilla/5.0 (Windows NT 6.2) AppleWebKit/536.6 " "(KHTML, like Gecko) Chrome/20.0.1090.0 Safari/536.6", "Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/537.1 " "(KHTML, like Gecko) Chrome/19.77.34.5 Safari/537.1", "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/536.5 " "(KHTML, like Gecko) Chrome/19.0.1084.9 Safari/536.5", "Mozilla/5.0 (Windows NT 6.0) AppleWebKit/536.5 " "(KHTML, like Gecko) Chrome/19.0.1084.36 Safari/536.5", "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.3 " "(KHTML, like Gecko) Chrome/19.0.1063.0 Safari/536.3", "Mozilla/5.0 (Windows NT 5.1) AppleWebKit/536.3 " "(KHTML, like Gecko) Chrome/19.0.1063.0 Safari/536.3", "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_8_0) AppleWebKit/536.3 " "(KHTML, like Gecko) Chrome/19.0.1063.0 Safari/536.3", "Mozilla/5.0 (Windows NT 6.2) AppleWebKit/536.3 " "(KHTML, like Gecko) Chrome/19.0.1062.0 Safari/536.3", "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.3 " "(KHTML, like Gecko) Chrome/19.0.1062.0 Safari/536.3", "Mozilla/5.0 (Windows NT 6.2) AppleWebKit/536.3 " "(KHTML, like Gecko) Chrome/19.0.1061.1 Safari/536.3", "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.3 " "(KHTML, like Gecko) Chrome/19.0.1061.1 Safari/536.3", "Mozilla/5.0 (Windows NT 6.1) AppleWebKit/536.3 " "(KHTML, like Gecko) Chrome/19.0.1061.1 Safari/536.3", "Mozilla/5.0 (Windows NT 6.2) AppleWebKit/536.3 " "(KHTML, like Gecko) Chrome/19.0.1061.0 Safari/536.3", "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/535.24 " "(KHTML, like Gecko) Chrome/19.0.1055.1 Safari/535.24", "Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/535.24 " "(KHTML, like Gecko) Chrome/19.0.1055.1 Safari/535.24" ] PROXY_http = [ '153.180.102.104:80', '195.208.131.189:56055', ] PROXY_https = [ '120.83.49.90:9000', '95.189.112.214:35508', ]
@classmethod def from_crawler(cls, crawler): # This method is used by Scrapy to create your spiders. s = cls() crawler.signals.connect(s.spider_opened, signal=signals.spider_opened) return s #可以处理拦截到所有的非异常的请求 #spider参数表示的就是爬虫类实例化的一个对象 def process_request(self, request, spider): print('this is process_request()') #UA伪装 request.headers['User-Agent'] = random.choice(self.user_agent_list) #测试：代理操作是否生效 request.meta['proxy'] = 'https://218.60.8.83:3129' return None
#拦截所有的响应 def process_response(self, request, response, spider): return response #拦截发生异常的请求对象，我们一般会将IP池放在这个方法中进行执行 def process_exception(self, request, exception, spider): if request.url.split(':')[0] == 'https': request.meta['proxy'] = 'https://'+random.choice(self.PROXY_https) else: request.meta['proxy'] = 'http://' + random.choice(self.PROXY_http) def spider_opened(self, spider): spider.logger.info('Spider opened: %s' % spider.name)
