21-爬虫之scrapy框架selenium的使用08

selenium在scrapy中的使用
案例：爬取网易新闻中，国内，国际，军事，航空，无人机这五个板块下的所有新闻数据（标题+内容）

基本使用

创建一个爬虫工程：scrapy startproject proName
进入工程创建一个基于CrawlSpider的爬虫文件
scrapy genspider spiderName www.xxx.com
执行工程：scrapy crawl spiderName

分析

• 首页非动态加载的数据
  • 在首页爬取板块对应的url
• 每一个板块对应的页面中的新闻是动态加载的
  • 爬取新闻标题+详情页url
  • 每一条新闻详情页面中的数据不是动态加载
    • 爬取详情页新闻内容
• selenium在scrapy中的使用流程
  • 1，在爬虫类中实例化一个浏览器对象，将其作为爬虫类的一个属性
  • 2，在中间件中实现浏览器自动化的相关操作
  • 3，在爬虫类中重写closed(self,spider)，再其内部关闭浏览器对象

settings.py

# Scrapy settings for SeleniumTest project
#
# For simplicity, this file contains only settings considered important or
# commonly used. You can find more settings consulting the documentation:
#
#     https://docs.scrapy.org/en/latest/topics/settings.html
#     https://docs.scrapy.org/en/latest/topics/downloader-middleware.html
#     https://docs.scrapy.org/en/latest/topics/spider-middleware.html

BOT_NAME = 'SeleniumTest'

SPIDER_MODULES = ['SeleniumTest.spiders']
NEWSPIDER_MODULE = 'SeleniumTest.spiders'


# Crawl responsibly by identifying yourself (and your website) on the user-agent
USER_AGENT = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/81.0.4044.138 Safari/537.36"

# Obey robots.txt rules
ROBOTSTXT_OBEY = False
LOG_LEVEL = "ERROR"

# Configure maximum concurrent requests performed by Scrapy (default: 16)
#CONCURRENT_REQUESTS = 32

# Configure a delay for requests for the same website (default: 0)
# See https://docs.scrapy.org/en/latest/topics/settings.html#download-delay
# See also autothrottle settings and docs
#DOWNLOAD_DELAY = 3
# The download delay setting will honor only one of:
#CONCURRENT_REQUESTS_PER_DOMAIN = 16
#CONCURRENT_REQUESTS_PER_IP = 16

# Disable cookies (enabled by default)
#COOKIES_ENABLED = False

# Disable Telnet Console (enabled by default)
#TELNETCONSOLE_ENABLED = False

# Override the default request headers:
#DEFAULT_REQUEST_HEADERS = {
#   'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
#   'Accept-Language': 'en',
#}

# Enable or disable spider middlewares
# See https://docs.scrapy.org/en/latest/topics/spider-middleware.html
#SPIDER_MIDDLEWARES = {
#    'SeleniumTest.middlewares.SeleniumtestSpiderMiddleware': 543,
#}

# Enable or disable downloader middlewares
# See https://docs.scrapy.org/en/latest/topics/downloader-middleware.html
DOWNLOADER_MIDDLEWARES = {
   'SeleniumTest.middlewares.SeleniumtestDownloaderMiddleware': 543,
}

# Enable or disable extensions
# See https://docs.scrapy.org/en/latest/topics/extensions.html
#EXTENSIONS = {
#    'scrapy.extensions.telnet.TelnetConsole': None,
#}

# Configure item pipelines
# See https://docs.scrapy.org/en/latest/topics/item-pipeline.html
ITEM_PIPELINES = {
   'SeleniumTest.pipelines.SeleniumtestPipeline': 300,
}

# Enable and configure the AutoThrottle extension (disabled by default)
# See https://docs.scrapy.org/en/latest/topics/autothrottle.html
#AUTOTHROTTLE_ENABLED = True
# The initial download delay
#AUTOTHROTTLE_START_DELAY = 5
# The maximum download delay to be set in case of high latencies
#AUTOTHROTTLE_MAX_DELAY = 60
# The average number of requests Scrapy should be sending in parallel to
# each remote server
#AUTOTHROTTLE_TARGET_CONCURRENCY = 1.0
# Enable showing throttling stats for every response received:
#AUTOTHROTTLE_DEBUG = False

# Enable and configure HTTP caching (disabled by default)
# See https://docs.scrapy.org/en/latest/topics/downloader-middleware.html#httpcache-middleware-settings
#HTTPCACHE_ENABLED = True
#HTTPCACHE_EXPIRATION_SECS = 0
#HTTPCACHE_DIR = 'httpcache'
#HTTPCACHE_IGNORE_HTTP_CODES = []
#HTTPCACHE_STORAGE = 'scrapy.extensions.httpcache.FilesystemCacheStorage'

middlewares.py

from scrapy import signals
from itemadapter import is_item, ItemAdapter
from scrapy.http import HtmlResponse #scrapy封装好的响应类
import time
class SeleniumtestDownloaderMiddleware:
    def process_request(self, request, spider):

        return None

    # 拦截所有的响应请求
    # 整个工程发起的请求：1+5+n个响应的响应对象也是1+5+n个
    # 只有指定的5个响应对象是不满足需求
    # 只将不满足需求的5个指定的响应对象的响应数据进行篡改
    def process_response(self, request, response, spider):
        # 将所有拦截到的响应对象中指定的5个响应对象找出
        if request.url in spider.model_urls:
            bro = spider.bro
            # response表示的就是指定的不满足需求的5个响应对象
            # 篡改响应数据：首先先获取满足需求的响应数据，将其篡改到响应对象中即可
            # 满足需求的响应数据就可以使用selenium获取
            bro.get(request.url)  # 对五个板块的url发起请求
            time.sleep(2)
            bro.execute_script('window.scrollTo(0,document.body.scrollHeight)')
            time.sleep(1)
            # 捕获到了板块页面中加载出来的全部数据（包含了动态加载的数据）
            page_text = bro.page_source

            # response.text = page_text
            # return response

            # 返回了一个新的响应对象，新的对象替换了原来不满足需求的旧响应对象
            return HtmlResponse(url=request.url, body=page_text, encoding="utf-8", request=request)  # 5
        else:
            return response  # 1+n

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

        pass

pipelines.py

# Define your item pipelines here
#
# Don't forget to add your pipeline to the ITEM_PIPELINES setting
# See: https://docs.scrapy.org/en/latest/topics/item-pipeline.html


# useful for handling different item types with a single interface
from itemadapter import ItemAdapter


class SeleniumtestPipeline:
    def process_item(self, item, spider):
        print(item)
        return item

items.py

# Define here the models for your scraped items
#
# See documentation in:
# https://docs.scrapy.org/en/latest/topics/items.html

import scrapy


class SeleniumtestItem(scrapy.Item):
    title = scrapy.Field()
    content = scrapy.Field()

test.py（爬虫源文件）

import scrapy
from selenium import webdriver
from SeleniumTest.items import SeleniumtestItem

class TestSpider(scrapy.Spider):
    name = 'test'
    # allowed_domains = ['www.xxx.com']
    start_urls = ['http://news.163.com/']
    model_urls = [] # 存放每一个板块对应的url

    # 实例化一个全局浏览器对象
    bro = webdriver.Chrome()
    # 数据解析：每一个板块对应的url
    def parse(self, response):
        li_list = response.xpath('//*[@id="index2016_wrap"]/div[1]/div[2]/div[2]/div[2]/div[2]/div/ul/li')
        indexs = [3,4,6,7,8]
        for index in indexs:
            model_li = li_list[index]
            mode_url = model_li.xpath('./a/@href').extract_first()
            self.model_urls.append(mode_url)
        #对每一个板块发起请求
        for url in self.model_urls:
            yield scrapy.Request(url=url,callback=self.parse_model)

    # 数据解析：新闻标题+新闻详情页的url（动态加载的数据）
    def parse_model(self,response):
        div_list = response.xpath('/html/body/div/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()
            new_detail_url = div.xpath('./div/div[1]/h3/a/@href').extract_first()
            if new_detail_url:
                item = SeleniumtestItem() # 实例化item对象
                item['title'] = title
                # 对新闻详情页url发起请求
                yield scrapy.Request(url=new_detail_url,callback=self.parse_new_detail,meta={'item':item})
    def parse_new_detail(self,response):
        # 解析新闻内容
        content = response.xpath('//*[@id="endText"]/p/text()').extract()
        content = ''.join(content)
        item = response.meta['item']
        item['content'] = content
        yield item

    # 关闭浏览器  爬虫类父类的方法，该方法是在爬虫结束最后一刻执行
    def closed(self,spider):
        self.bro.quit()