text: # -*- coding: utf-8 -*-
  
  # Define here the models for your spider middleware
  #
  # See documentation in:
  # https://doc.scrapy.org/en/latest/topics/spider-middleware.html
  
  import random
  
  import requests
  from scrapy import signals
  
  
  class DoubanSpiderMiddleware(object):
      # Not all methods need to be defined. If a method is not defined,
      # scrapy acts as if the spider middleware does not modify the
      # passed objects.
  
      @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
  
      def process_spider_input(self, response, spider):
          # Called for each response that goes through the spider
          # middleware and into the spider.
  
          # Should return None or raise an exception.
          return None
  
      def process_spider_output(self, response, result, spider):
          # Called with the results returned from the Spider, after
          # it has processed the response.
  
          # Must return an iterable of Request, dict or Item objects.
          for i in result:
              yield i
  
      def process_spider_exception(self, response, exception, spider):
          # Called when a spider or process_spider_input() method
          # (from other spider middleware) raises an exception.
  
          # Should return either None or an iterable of Response, dict
          # or Item objects.
          pass
  
      def process_start_requests(self, start_requests, spider):
          # Called with the start requests of the spider, and works
          # similarly to the process_spider_output() method, except
          # that it doesn’t have a response associated.
  
          # Must return only requests (not items).
          for r in start_requests:
              yield r
  
      def spider_opened(self, spider):
          spider.logger.info('Spider opened: %s' % spider.name)
  
  
  class DoubanDownloaderMiddleware(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.
  
      @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
  
      def process_request(self, request, spider):
          # Called for each request that goes through the downloader
          # middleware.
  
          # Must either:
          # - return None: continue processing this request
          # - or return a Response object
          # - or return a Request object
          # - or raise IgnoreRequest: process_exception() methods of
          #   installed downloader middleware will be called
          return None
  
      def process_response(self, request, response, spider):
          # Called with the response returned from the downloader.
  
          # Must either;
          # - return a Response object
          # - return a Request object
          # - or raise IgnoreRequest
          return response
  
      def process_exception(self, request, exception, spider):
          # Called when a download handler or a process_request()
          # (from other downloader middleware) raises an exception.
  
          # Must either:
          # - return None: continue processing this exception
          # - return a Response object: stops process_exception() chain
          # - return a Request object: stops process_exception() chain
          pass
  
      def spider_opened(self, spider):
          spider.logger.info('Spider opened: %s' % spider.name)
  
  
  class RandomChangeUserAgentMiddleware(object):
      """
      随机变换UserAgent请求消息头中间件
      """
  
      def __init__(self, user_agent_list):
          self.user_agent_list = user_agent_list
  
      @classmethod
      def from_crawler(cls, crawler):
          return cls(crawler.settings.get('USER_AGENT_LIST'))
  
      def process_request(self, request, spider):
          user_agent = random.choice(self.user_agent_list)
          request.headers['User-Agent'] = user_agent
  
  
  class RandomChangeProxyIpMiddleware(object):
      """
      随机变换代理IP中间件
      """
  
      def __init__(self, proxies):
          self.proxies = proxies
  
      @classmethod
      def from_crawler(cls, crawler):
          # 程序启动时，动态获取一批代理IP，供后续随机切换使用
          proxies = ['181.30.3.234:3128', '58.11.67.120:3128', '201.166.23.226:8080', '109.197.188.8:8080',
                     '88.99.149.188:31288', '93.87.28.42:53281', '49.48.130.147:8080', '212.8.252.110:1080',
                     '101.96.10.4:80', '101.96.10.63:8080']
          return cls(proxies)
  
      def process_request(self, request, spider):
          # 代理IP来源于西刺代理，不过质量并不高，很多不能用
          # http://www.xicidaili.com/nn/
          # request.meta['proxy'] = 'http://118.190.95.43:9001'
          # 后改为从 https://github.com/jhao104/proxy_pool 提供的测试地址获取
          # http://123.207.35.36:5010/get/
          request.meta['proxy'] = random.choice(self.proxies)
  