scrapy 中间件

下载中间件的应用

scrapy中间件有:-爬虫中间件，下载中间件
下载中间件应用较多
下载中间件：
- 作用：批量拦截请求和响应
- 拦截请求：
- UA伪装：将所有的请求尽可能多的设定成不同的请求载体身份标识
  - request.headers['User-Agent'] = 'xxx'
- 代理操作：request.meta['proxy'] = 'http://ip:port'
- 拦截响应：篡改响应数据或者直接替换响应对象

1 拦截请求中间件

作用:
- UA伪装：将所有的请求尽可能多的设定成不同的请求载体身份标识
  - request.headers['User-Agent'] = 'xxx'
- 代理操作：request.meta['proxy'] = 'http://ip:port'

爬取4567视频网示例:

spider.py文件

import scrapy
from moviespider.items import MoviespiderItem

class MovieSpiderSpider(scrapy.Spider):
    name = 'movie_spider'
    # allowed_domains = ['https://www.4567tv.tv/index.php/vod/show/class/动作/id/1.html']
    start_urls = ['https://www.4567tv.tv/index.php/vod/show/class/动作/id/1.html']
    url = 'https://www.4567tv.tv/index.php/vod/show/class/动作/id/1/page/%d.html'
    pageNum = 1

    def parse(self, response):
        li_list = response.xpath('/html/body/div[1]/div/div/div/div[2]/ul/li')
        for li in li_list:
            title = li.xpath('./div[1]/a/@title').extract_first()
            detail_url = 'https://www.4567tv.tv' + li.xpath('./div[1]/a/@href').extract_first()
            item = MoviespiderItem()
            item['title'] = title
            # meta参数是一个字典，该字典就可以传递给callback指定的回调函数
            yield scrapy.Request(detail_url, callback=self.parse_detail, meta={"item": item})

    def parse_detail(self, response):
        # 接收meta：response.meta
        item = response.meta['item']
        desc = response.xpath('/html/body/div[1]/div/div/div/div[2]/p[5]/span[2]/text()').extract_first()
        item["desc"] = desc
        yield item

items.py
- 创建title和desc的属性
pipelines.py文件
- 存储

middleware.py

downloadmiddleware文件

from scrapy import signals
import random

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",
]  # 常见浏览器user_agent

PROXY_http = [
    '153.180.102.104:80',
]
PROXY_https = [
    '120.83.49.90:9000',
]


class MoviespiderDownloaderMiddleware(object):

    # 拦截正常的请求，参数request就是拦截到的请求对象
    def process_request(self, request, spider):
        print('i am process_request()')
        # 实现：将拦截到的请求尽可能多的设定成不同的请求载体身份标识
        request.headers['User-Agent'] = random.choice(user_agent_list)
        # 代理操作
        if request.url.split(':')[0] == 'http':
            request.meta['proxy'] = 'http://' + random.choice(PROXY_http)  # http://ip:port
        else:
            request.meta['proxy'] = 'https://' + random.choice(PROXY_https)  # http://ip:port

        return

    # 拦截响应：参数response就是拦截到的响应
    def process_response(self, request, response, spider):
        print('i am process_response()')
        return response

    def process_exception(self, request, exception, spider):
        print('i am process_exception()')
        # 拦截到异常的请求然后对其进行修正，然后重新进行请求发送
        # 代理操作
        if request.url.split(':')[0] == 'http':
            request.meta['proxy'] = 'http://' + random.choice(PROXY_http)  # http://ip:port
        else:
            request.meta['proxy'] = 'https://' + random.choice(PROXY_https)  # http://ip:port

        return request  # 将修正之后的请求进行重新发送

常用浏览器user_agent

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"
]

2 拦截响应中间件

作用:拦截响应可以篡改响应数据或者直接替换响应对象
selenium在scrapy中的应用:
- 实例化浏览器对象：写在爬虫类的构造方法中
- 关闭浏览器：爬虫类中的closed(self,spider)关闭浏览器
- 在中间件中执行浏览器自动化的操作

示例:

需求; 爬取网易新闻的国内，国际，军事，航空，无人机这五个板块下对应的新闻标题和内容(数据是动态加载的)

spider.py文件

# -*- coding: utf-8 -*-
import scrapy
from selenium import webdriver
from wangyinews.item import WangyinewsItem

class NewsSpider(scrapy.Spider):
    name = 'news'
    # allowed_domains = ['www.wangyi.com']
    start_urls = ['https://news.163.com']
    five_model_urls = []
    bro = webdriver.Chrome(executable_path=r'D:\教学视频\python 爬虫\tools\chromedriver.exe')

    # 用来解析五个板块对应的url，然后对其进行手动请求发送
    def parse(self, response):
        model_index = [3, 4, 6, 7, 8]
        li_list = response.xpath('//*[@id="index2016_wrap"]/div[1]/div[2]/div[2]/div[2]/div[2]/div/ul/li')
        for index in model_index:
            li = li_list[index]
            # 获取了五个板块对应的url
            model_url = li.xpath('./a/@href').extract_first()
            self.five_model_urls.append(model_url)
            # 对每一个板块的url进行手动i请求发送
            yield scrapy.Request(model_url, callback=self.parse_model)

    # 解析每一个板块页面中的新闻标题和新闻详情页的url
    # 问题：response（不满足需求的response）中并没有包含每一个板块中动态加载出的新闻数据
    def parse_model(self, response):
        div_list = response.xpath('/html/body/div[1]/div[3]/div[4]/div[1]/div/div/ul/li/div/div')
        for div in div_list:
            title = div.xpath('./div/div[1]/h3/a/text()').extract_first()
            detail_url = div.xpath('./div/div[1]/h3/a/@href').extract_first()
            item = WangyinewsItem()
            item['title'] = title
            # 对详情页发起请求解析出新闻内容
            yield scrapy.Request(detail_url, callback=self.parse_new_content, meta={'item': item})

    # 获取内容详情
    def parse_new_content(self, response):
        item = response.meta["item"]
        content = response.xpath('//*[@id="endText"]//text()').extract()
        item["content"] = content
        yield item

    # 最后执行,关闭bro
    def close(self, spider):
        self.bro.quit()

items.py
- 创建title和desc的属性
pipelines.py文件
- 存储

middleware.py文件:

# -*- coding: utf-8 -*-

# Define here the models for your spider middleware
#
# See documentation in:
# https://docs.scrapy.org/en/latest/topics/spider-middleware.html
from time import sleep

from scrapy import signals
from scrapy.http import HtmlResponse


class WangyinewsDownloaderMiddleware(object):

    def process_request(self, request, spider):
        return None

    def process_response(self, request, response, spider):
        # spider就是爬虫文件中爬虫类实例化的对象
        # 进行所有响应对象的拦截
        # 1.将所有的响应中那五个不满足需求的响应对象找出
        # 1.每一个响应对象对应唯一一个请求对象
        # 2.如果我们可以定位到五个响应对应的请求对象后，就可以通过该i请求对象定位到指定的响应对象
        # 3.可以通过五个板块的url定位请求对象
        # 总结： url==》request==》response
        # 2.将找出的五个不满足需求的响应对象进行修正（替换）
        # spider.five_model_urls:五个板块对应的url
        bro = spider.bro
        if request.url in spider.five_model_urls:
            bro.get(request.url)
            sleep(1)
            page_text = bro.page_source  # 包含了动态加载的新闻数据
            # 如果if条件程利则该response就是五个板块对应的响应对象
            new_responde = HtmlResponse(url=request.url, body=page_text, encoding="utf-8", request=request)
            return new_responde
        return response

    def process_exception(self, request, exception, spider):
        pass

posted @ 2019-09-02 17:54 高薪程序员阅读(304) 评论(0) 编辑收藏举报

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scrapy 中间件

下载中间件的应用

1 拦截请求中间件

2 拦截响应中间件

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