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'

 数据：