scrapy框架只能爬取静态网站。如需爬取动态网站，需要结合着selenium进行js的渲染，才能获取到动态加载的数据。

如何通过selenium请求url，而不再通过下载器Downloader去请求这个url?

方法：在request对象通过中间件的时候，在中间件内部开始使用selenium去请求url，并且会得到url对应的源码，然后再将 源 代码通过response对象返回，直接交给process_response()进行处理，再交给引擎。过程中相当于后续中间件的process_request()以及Downloader都跳过了。

相关的配置：

1、scrapy环境中安装selenium：pip install selenium

2、确保python环境中有phantomJS（无头浏览器）

对于selenium的主要操作是下载中间件部分如下图：

代码如下

middlewares.py代码：

注意：自定义下载中间件，采用selenium的方式！！

# -*- coding: utf-8 -*-# Define here the models for your spider middleware## See documentation in:# https://doc.scrapy.org/en/latest/topics/spider-middleware.htmlfrom scrapy import signalsfrom selenium import webdriverfrom selenium.webdriver import FirefoxOptionsfrom scrapy.http import HtmlResponse, Responseimport timeclass TaobaospiderSpiderMiddleware(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 TaobaospiderDownloaderMiddleware(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)*********************下面是相应是自定义的下载中间件的替换代码**************************class SeleniumTaobaoDownloaderMiddleware(object): # 将driver创建在中间件的初始化方法中，适合项目中只有一个爬虫。 # 爬虫项目中有多个爬虫文件的话，将driver对象的创建放在每一个爬虫文件中。 # def __init__(self): # # 在scrapy中创建driver对象，尽可能少的创建该对象。 # # 1. 在初始化方法中创建driver对象； # # 2. 在open_spider中创建deriver对象； # # 3. 不要将driver对象的创建放在process_request()； # option = FirefoxOptions() # option.headless = True # self.driver = webdriver.Firefox(options=option) # 参数spider就是TaobaoSpider()类的对象 def process_request(self, request, spider): if spider.name == "taobao": spider.driver.get(request.url) # 由于淘宝的页面数据加载需要进行滚动，但并不是所有js动态数据都需要滚动。 for x in range(1, 11, 2): height = float(x) / 10 js = "document.documentElement.scrollTop = document.documentElement.scrollHeight * %f" % height spider.driver.execute_script(js) time.sleep(0.2) origin_code = spider.driver.page_source # 将源代码构造成为一个Response对象，并返回。 res = HtmlResponse(url=request.url, encoding='utf8', body=origin_code, request=request) # res = Response(url=request.url, body=bytes(origin_code), request=request) return res if spider.name == 'bole': request.cookies = {} request.headers.setDefault('User-Agent','') return None def process_response(self, request, response, spider): print(response.url, response.status) return response

taobao.py 代码如下：

# -*- coding: utf-8 -*-import scrapyfrom selenium import webdriverfrom selenium.webdriver import FirefoxOptionsclass TaobaoSpider(scrapy.Spider): """ scrapy框架只能爬取静态网站。如需爬取动态网站，需要结合着selenium进行js的渲染，才能获取到动态加载的数据。 如何通过selenium请求url，而不再通过下载器Downloader去请求这个url? 方法：在request对象通过中间件的时候，在中间件内部开始使用selenium去请求url，并且会得到url对应的源码，然后再将源代码通过response对象返回，直接交给process_response()进行处理，再交给引擎。过程中相当于后续中间件的process_request()以及Downloader都跳过了。 """ name = 'taobao' allowed_domains = ['taobao.com'] start_urls = ['https://s.taobao.com/search?q=%E7%AC%94%E8%AE%B0%E6%9C%AC%E7%94%B5%E8%84%91&imgfile=&commend=all&ssid=s5-e&search_type=item&sourceId=tb.index&spm=a21bo.2017.201856-taobao-item.1&ie=utf8&initiative_id=tbindexz_20170306'] def __init__(self): # 在初始化淘宝对象时，创建driver super(TaobaoSpider, self).__init__(name='taobao') option = FirefoxOptions() option.headless = True self.driver = webdriver.Firefox(options=option) def parse(self, response): """ 提取列表页的商品标题和价格 :param response: :return: """ info_divs = response.xpath('//div[@class="info-cont"]') print(len(info_divs)) for div in info_divs: title = div.xpath('.//a[@class="product-title"]/@title').extract_first('') price = div.xpath('.//span[contains(@class, "g_price")]/strong/text()').extract_first('') print(title, price)

settings.py代码如下图：

关于代码中提到的初始化driver的位置有以下两种情况：

1、只存在一个爬虫文件的话，driver初始化函数可以定义在middlewares.py的自定义中间件中（如上述代码注释初始化部分）也可以在爬虫文件中自定义（如上述代码在爬虫文件中初始化）。

注意：如果只有一个爬虫文件就不需要在自定义的process_requsests中判断是哪一个爬虫项目然后分别请求！

2、如果存在两个或两个以上爬虫项目（如下图项目结构）的时候，需要将driver的初始化函数定义在各自的爬虫项目文件下（如上述代码），同时需要在process_requsests判断是那个爬虫项目的请求！！

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