目前，為了加速頁面的載入速度，頁面的很多部分都是用JS生成的，而對於用scrapy爬蟲來說就是一個很大的問題，因為scrapy沒有JS engine，所以爬取的都是靜態頁面，對於JS生成的動態頁面都無法獲得

　　解決方案：

　　1、利用第三方中介軟體來提供JS渲染服務： scrapy-splash 等。

　　2、利用webkit或者基於webkit庫

　Splash是一個Javascript渲染服務。它是一個實現了HTTP API的輕量級瀏覽器，Splash是用Python實現的，同時使用Twisted和QT。Twisted（QT）用來讓服務具有非同步處理能力，以發揮webkit的併發能力。

　　下面就來講一下如何使用scrapy-splash：

　　1、利用pip安裝scrapy-splash庫：

　　2、pip install scrapy-splash

　　　　scrapy-splash使用的是Splash HTTP API， 所以需要一個splash instance，一般採用docker執行splash，所以需要安裝docker，具體參見：http://www.cnblogs.com/shaosks/p/6932319.html

　　　　 安裝好後執行docker。docker成功安裝後，有“Docker Quickstart Terminal”圖示，雙擊他啟動

　　5、拉取映象(pull the image)：

　　　　　$ docker pull scrapinghub/splash

 　　　　這樣就正式啟動了。

　　6、用docker執行scrapinghub/splash服務：

　　　$ docker run -p 8050:8050 scrapinghub/splash

　　　　首次啟動會比較慢，載入一些東西，多次啟動會出現以下資訊

　　　　這時要關閉當前視窗，然後在程序管理器裡面關閉一些程序重新開啟

　　　　重新開啟Docker Quickstart Terminal，然後輸入：docker run -p 8050:8050 scrapinghub/splash

　　　7、配置splash服務（以下操作全部在settings.py）：

　　　　1）新增splash伺服器地址：

　　　　2）將splash middleware新增到DOWNLOADER_MIDDLEWARE中：

　　　　3)Enable SplashDeduplicateArgsMiddleware:

　　　　4)Set a custom DUPEFILTER_CLASS:

　　　　5)a custom cache storage backend:

 　　　8、正式抓取

　　　　 如下圖：框住的資訊是要榨取的內容

　　　　對應的html

　　　　1、京東價：

　　　　抓取程式碼：prices = site.xpath('//span[@class="p-price"]/span/text()')

　　　　2、促銷

　　　　抓取程式碼：cxs = site.xpath('//div[@class="J-prom-phone-jjg"]/em/text()')

　　　　3、增值業務

　　　　抓取程式碼：value_addeds =site.xpath('//ul[@class="choose-support lh"]/li/a/span/text()')

　　　　4、重量

　　　　抓取程式碼：quality = site.xpath('//div[@id="summary-weight"]/div[2]/text()')

　　　　5、選擇顏色

　　　　抓取程式碼：colors = site.xpath('//div[@id="choose-attr-1"]/div[2]/div/@title')

　　　　6、選擇版本

　　　　抓取程式碼：versions = site.xpath('//div[@id="choose-attr-2"]/div[2]/div/@data-value')

　　　　7、購買方式

　　　　抓取程式碼：buy_style = site.xpath('//div[@id="choose-type"]/div[2]/div/a/text()')

　　　　8、套　　裝

　　　　抓取程式碼：suits = site.xpath('//div[@id="choose-suits"]/div[2]/div/a/text()')

　　　　9、增值保障

　　　　抓取程式碼：vaps = site.xpath('//div[@class="yb-item-cat"]/div[1]/span[1]/text()')

　　　　10、白條分期

　　　　抓取程式碼：stagings = site.xpath('//div[@class="baitiao-list J-baitiao-list"]/div[@class="item"]/a/strong/text()')

 　　　 9、執行splash服務

　　　　　　在抓取之前首先要啟動splash服務，命令：docker run -p 8050:8050 scrapinghub/splash，

　　　　 點選“Docker Quickstart Terminal” 圖示

　　　　10、執行scrapy crawl scrapy_splash

　　　　11、抓取資料

　　　　12、完整原始碼

　　　　　　1、SplashSpider

# -*- coding: utf-8 -*-
import scrapy
from scrapy import Request
from scrapy.spiders import Spider
from scrapy_splash import SplashRequest
from scrapy_splash import SplashMiddleware
from scrapy.http import Request, HtmlResponse
from scrapy.selector import Selector
from scrapy_splash import SplashRequest
from splash_test.items import SplashTestItem
import sys
reload(sys)
sys.setdefaultencoding('utf-8')
sys.stdout = open('output.txt', 'w')

class SplashSpider(Spider):
    name = 'scrapy_splash'
    start_urls = [
        'https://item.jd.com/2600240.html'
    ]

    # request需要封裝成SplashRequest
    def start_requests(self):
        for url in self.start_urls:
            yield SplashRequest(url
                                , self.parse
                                , args={'wait': '0.5'}
                                # ,endpoint='render.json'
                                )

    def parse(self, response):

        # 本文只抓取一個京東連結，此連結為京東商品頁面，價格引數是ajax生成的。會把頁面渲染後的html存在html.txt
        # 如果想一直抓取可以使用CrawlSpider，或者把下面的註釋去掉
        site = Selector(response)
        it_list = []
        it = SplashTestItem()
        #京東價
        # prices = site.xpath('//span[@class="price J-p-2600240"]/text()')
        # it['price']= prices[0].extract()
        # print '京東價：'+ it['price']
        prices = site.xpath('//span[@class="p-price"]/span/text()')
        it['price'] = prices[0].extract()+ prices[1].extract()
        print '京東價：' + it['price']

        # 促　　銷
        cxs = site.xpath('//div[@class="J-prom-phone-jjg"]/em/text()')
        strcx = ''
        for cx in cxs:
            strcx += str(cx.extract())+' '
        it['promotion'] = strcx
        print '促銷:%s '% strcx

        # 增值業務
        value_addeds =site.xpath('//ul[@class="choose-support lh"]/li/a/span/text()')
        strValueAdd =''
        for va in value_addeds:
            strValueAdd += str(va.extract())+' '
        print '增值業務:%s ' % strValueAdd
        it['value_add'] = strValueAdd

        # 重量
        quality = site.xpath('//div[@id="summary-weight"]/div[2]/text()')
        print '重量:%s ' % str(quality[0].extract())
        it['quality']=quality[0].extract()

        #選擇顏色
        colors = site.xpath('//div[@id="choose-attr-1"]/div[2]/div/@title')
        strcolor = ''
        for color in colors:
            strcolor += str(color.extract()) + ' '
        print '選擇顏色:%s ' % strcolor
        it['color'] = strcolor

        # 選擇版本
        versions = site.xpath('//div[@id="choose-attr-2"]/div[2]/div/@data-value')
        strversion = ''
        for ver in versions:
            strversion += str(ver.extract()) + ' '
        print '選擇版本:%s ' % strversion
        it['version'] = strversion

        # 購買方式
        buy_style = site.xpath('//div[@id="choose-type"]/div[2]/div/a/text()')
        print '購買方式:%s ' % str(buy_style[0].extract())
        it['buy_style'] = buy_style[0].extract()

        # 套裝
        suits = site.xpath('//div[@id="choose-suits"]/div[2]/div/a/text()')
        strsuit = ''
        for tz in suits:
            strsuit += str(tz.extract()) + ' '
        print '套裝:%s ' % strsuit
        it['suit'] = strsuit

        # 增值保障
        vaps = site.xpath('//div[@class="yb-item-cat"]/div[1]/span[1]/text()')
        strvaps = ''
        for vap in vaps:
            strvaps += str(vap.extract()) + ' '
        print '增值保障:%s ' % strvaps
        it['value_add_protection'] = strvaps

        # 白條分期
        stagings = site.xpath('//div[@class="baitiao-list J-baitiao-list"]/div[@class="item"]/a/strong/text()')
        strstaging = ''
        for st in stagings:
            ststr =str(st.extract())
            strstaging += ststr.strip() + ' '
        print '白天分期:%s ' % strstaging
        it['staging'] = strstaging

        it_list.append(it)
        return it_list

 　　　2、SplashTestItem

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

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

import scrapy


class SplashTestItem(scrapy.Item):
    #單價
    price = scrapy.Field()
    # description = Field()
    #促銷
    promotion = scrapy.Field()
    #增值業務
    value_add = scrapy.Field()
    #重量
    quality = scrapy.Field()
    #選擇顏色
    color = scrapy.Field()
    #選擇版本
    version = scrapy.Field()
    #購買方式
    buy_style=scrapy.Field()
    #套裝
    suit =scrapy.Field()
    #增值保障
    value_add_protection = scrapy.Field()
    #白天分期
    staging = scrapy.Field()
    # post_view_count = scrapy.Field()
    # post_comment_count = scrapy.Field()
    # url = scrapy.Field()

　　　　3、SplashTestPipeline

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

# Define your item pipelines here
#
# Don't forget to add your pipeline to the ITEM_PIPELINES setting
# See: http://doc.scrapy.org/en/latest/topics/item-pipeline.html
import codecs
import json

class SplashTestPipeline(object):
    def __init__(self):
        # self.file = open('data.json', 'wb')
        self.file = codecs.open(
            'spider.txt', 'w', encoding='utf-8')
        # self.file = codecs.open(
        #     'spider.json', 'w', encoding='utf-8')

    def process_item(self, item, spider):
        line = json.dumps(dict(item), ensure_ascii=False) + "\n"
        self.file.write(line)
        return item

    def spider_closed(self, spider):
        self.file.close()

　　　4、settings.py

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

# Scrapy settings for splash_test project
#
# For simplicity, this file contains only settings considered important or
# commonly used. You can find more settings consulting the documentation:
#
#     http://doc.scrapy.org/en/latest/topics/settings.html
#     http://scrapy.readthedocs.org/en/latest/topics/downloader-middleware.html
#     http://scrapy.readthedocs.org/en/latest/topics/spider-middleware.html
ITEM_PIPELINES = {
        'splash_test.pipelines.SplashTestPipeline':300
        }
BOT_NAME = 'splash_test'

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

SPLASH_URL = 'http://192.168.99.100:8050'
# Crawl responsibly by identifying yourself (and your website) on the user-agent
#USER_AGENT = 'splash_test (+http://www.yourdomain.com)'

# Obey robots.txt rules
ROBOTSTXT_OBEY = True

DOWNLOADER_MIDDLEWARES = {
    'scrapy_splash.SplashCookiesMiddleware': 723,
    'scrapy_splash.SplashMiddleware': 725,
    'scrapy.downloadermiddlewares.httpcompression.HttpCompressionMiddleware': 810,
}
SPIDER_MIDDLEWARES = {
    'scrapy_splash.SplashDeduplicateArgsMiddleware': 100,
}
DUPEFILTER_CLASS = 'scrapy_splash.SplashAwareDupeFilter'
HTTPCACHE_STORAGE = 'scrapy_splash.SplashAwareFSCacheStorage'
# Configure maximum concurrent requests performed by Scrapy (default: 16)
#CONCURRENT_REQUESTS = 32

# Configure a delay for requests for the same website (default: 0)
# See http://scrapy.readthedocs.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 http://scrapy.readthedocs.org/en/latest/topics/spider-middleware.html
#SPIDER_MIDDLEWARES = {
#    'splash_test.middlewares.SplashTestSpiderMiddleware': 543,
#}

# Enable or disable downloader middlewares
# See http://scrapy.readthedocs.org/en/latest/topics/downloader-middleware.html
#DOWNLOADER_MIDDLEWARES = {
#    'splash_test.middlewares.MyCustomDownloaderMiddleware': 543,
#}

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

# Configure item pipelines
# See http://scrapy.readthedocs.org/en/latest/topics/item-pipeline.html
#ITEM_PIPELINES = {
#    'splash_test.pipelines.SplashTestPipeline': 300,
#}

# Enable and configure the AutoThrottle extension (disabled by default)
# See http://doc.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 http://scrapy.readthedocs.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'