scrapy实战3利用fiddler对手机app进行抓包爬虫图片下载（重写ImagesPipeline）：

关于fiddler的使用方法参考（http://jingyan.baidu.com/article/03b2f78c7b6bb05ea237aed2.html）

本案例爬取斗鱼 app

先利用fiddler分析抓包json数据如下图

通过分析发现变化的只有offset  确定item字段 开始编写代码

items.py

 import scrapy

 class DouyuItem(scrapy.Item):
     # define the fields for your item here like:
     # name = scrapy.Field()
     # 存储照片的名字
     nickname=scrapy.Field()
     # 照片的url路径
     imagelink=scrapy.Field()
     # 照片保存在本地的路径
     imagepath=scrapy.Field()

spider/Douyu.py

 import scrapy
 import json
 from douyu.items import DouyuItem

 class DouyuSpider(scrapy.Spider):
     name = "Douyu"
     allowed_domains = ["capi.douyucdn.cn"]
     offset=0
     url="http://capi.douyucdn.cn/api/v1/getVerticalRoom?limit=20&offset="
     start_urls = [url+str(offset)]

     def parse(self, response):
         # 将从json里获取的数据转换成python对象 data段数据集合 response.text获取内容
         data=json.loads(response.text)["data"]
         for each in data:
             item=DouyuItem()
             item["nickname"]=each["nickname"]
             item["imagelink"]=each["vertical_src"]
             yield item
         self.offset+=100
         yield scrapy.Request(self.url+str(self.offset),callback=self.parse)

pipelines.py

import scrapy
from scrapy.pipelines.images import ImagesPipeline
from douyu.items import DouyuItem
from scrapy.utils.project import get_project_settings
import os
class DouyuPipeline(object):
    def process_item(self, item, spider):
        return item
class ImagesPipelines(ImagesPipeline):

    IMAGES_STORE=get_project_settings().get("IMAGES_STORE")
    def get_media_requests(self, item, info):
        # get_media_requests的作用就是为每一个图片链接生成一个Request对象，这个方法的输出将作为item_completed的输入中的results，results是一个元组，
        # 每个元组包括(success, imageinfoorfailure)。如果success=true，imageinfoor_failure是一个字典，包括url/path/checksum三个key。
        image_url=item["imagelink"]
        yield scrapy.Request(image_url)
    def item_completed(self, results, item, info):
        # 固定写法，获取图片路径，同时判断这个路径是否正确，如果正确，就放到 image_path里，ImagesPipeline源码剖析可见
        image_path=[x["path"] for ok,x in results if ok]
        print(image_path)
        os.rename(self.IMAGES_STORE+'/'+image_path[0],self.IMAGES_STORE+"/"+item["nickname"]+".jpg")
        item["imagepath"]=self.IMAGES_STORE+"/"+item["nickname"]

settints.py

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

 # Scrapy settings for douyu 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
 import os
 BOT_NAME = 'douyu'

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

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

 # Obey robots.txt rules
 ROBOTSTXT_OBEY = False

 # 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 = {
     "USER_AGENT" : 'DYZB/2.290 (iPhone; iOS 9.3.4; Scale/2.00)'
 #   '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 = {
 #    'douyu.middlewares.DouyuSpiderMiddleware': 543,
 #}

 # Enable or disable downloader middlewares
 # See http://scrapy.readthedocs.org/en/latest/topics/downloader-middleware.html
 #DOWNLOADER_MIDDLEWARES = {
 #    'douyu.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 = {
     # 'scrapy.pipelines.images.ImagesPipeline': 1,
      'douyu.pipelines.ImagesPipelines': 300,
 }
 # Images 的存放位置，之后会在pipelines.py里调用
 project_dir=os.path.abspath(os.path.dirname(__file__))
 IMAGES_STORE=os.path.join(project_dir,'images') #images可以随便取名
 # 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'

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