由于scrapy自己的FilePipeline是用下载url的hash码来给文件命名的，所以想要定制自己的filepipeline，给文件重新命名。于是google了一下，发现大家都说是：继承FilesPipeline类然后重写get_media_requests和file_path方法，大致的代码如下：

import scrapy
from scrapy.pipelines.images import FilesPipeline
from scrapy.exceptions import DropItem

class MyFilesPipeline(FilesPipeline):

    def get_media_requests(self, item, info):
        file_url = item['file_url']
        meta = {'filename': item['name']}
        yield Request(url=file_url, meta=meta)
        
    def file_path(self, request, response=None, info=None):
        return request.meta.get('filename','')

但我希望给文件命的名字，是要从下载链接的响应的头信息中获取的，具体来说是从response.headers.get('Content-Disposition')中提取。于是我这样重写file_path方法：

    def file_path(self, request, response=None, info=None):
        pattern = re.compile(r'filename=(.*)')
        filename = pattern.search(r.headers['Content-Disposition'].encode('ISO-8859-1').decode('gbk')).group(1)
        return filename

但发现这样写，连文件都下载不了了。请问问题在哪里？另外，貌似file_path方法中的response是空的，为什么？

========================================================

更具体的代码，我的Pipeline长这样：

class MyfilesPipeline(FilesPipeline):
    def get_media_requests(self, item, info):
        return [scrapy.Request(x) for x in item.get(self.files_urls_field, [])]

    def file_path(self, request, response=None, info=None):
        pattern = re.compile(r'filename=(.*)')
        containFileName = response.headers.get('Content-Disposition').decode('gbk')
        filename = pattern.search(containFileName).group(1)
        return 'full/%s' % filename

但跑的结果：

2018-04-02 17:14:46 [scrapy.middleware] INFO: Enabled downloader middlewares:
['scrapy.downloadermiddlewares.httpauth.HttpAuthMiddleware',
 'scrapy.downloadermiddlewares.downloadtimeout.DownloadTimeoutMiddleware',
 'scrapy.downloadermiddlewares.defaultheaders.DefaultHeadersMiddleware',
 'scrapy.downloadermiddlewares.useragent.UserAgentMiddleware',
 'scrapy.downloadermiddlewares.retry.RetryMiddleware',
 'scrapy.downloadermiddlewares.redirect.MetaRefreshMiddleware',
 'scrapy.downloadermiddlewares.httpcompression.HttpCompressionMiddleware',
 'scrapy.downloadermiddlewares.redirect.RedirectMiddleware',
 'scrapy.downloadermiddlewares.cookies.CookiesMiddleware',
 'scrapy.downloadermiddlewares.httpproxy.HttpProxyMiddleware',
 'scrapy.downloadermiddlewares.stats.DownloaderStats']
2018-04-02 17:14:46 [scrapy.middleware] INFO: Enabled spider middlewares:
['scrapy.spidermiddlewares.httperror.HttpErrorMiddleware',
 'scrapy.spidermiddlewares.offsite.OffsiteMiddleware',
 'scrapy.spidermiddlewares.referer.RefererMiddleware',
 'scrapy.spidermiddlewares.urllength.UrlLengthMiddleware',
 'scrapy.spidermiddlewares.depth.DepthMiddleware']
2018-04-02 17:14:46 [scrapy.middleware] INFO: Enabled item pipelines:
['cszgSpider.pipelines.MyfilesPipeline',
 'cszgSpider.pipelines.CszgspiderPipeline']
2018-04-02 17:14:46 [scrapy.core.engine] INFO: Spider opened
2018-04-02 17:14:46 [scrapy.extensions.logstats] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
2018-04-02 17:14:46 [scrapy.extensions.telnet] DEBUG: Telnet console listening on 127.0.0.1:6023
2018-04-02 17:14:46 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://cishan.chinanpo.gov.cn/biz/ma/csmh/d/csmhddoSort.html?pageNo=1&;search_condit=&sort=desc&flag=0> (referer: None)
2018-04-02 17:14:47 [scrapy.core.scraper] DEBUG: Scraped from <200 http://cishan.chinanpo.gov.cn/biz/ma/csmh/d/csmhddoSort.html?pageNo=1&;search_condit=&sort=desc&flag=0>
{'file_urls': ['http://cishan.chinanpo.gov.cn/mz/upload/pub/load/resource_download.html?resourceid=ff80808162718ac70162854c92690082',
               'http://cishan.chinanpo.gov.cn/mz/upload/pub/load/resource_download.html?resourceid=ff808081627192280162853fdb1501e1',
               'http://cishan.chinanpo.gov.cn/mz/upload/pub/load/resource_download.html?resourceid=ff80808162718ac701627b3fd553004f',
               'http://cishan.chinanpo.gov.cn/mz/upload/pub/load/resource_download.html?resourceid=ff80808162718ac7016275e8bcda0039',
               'http://cishan.chinanpo.gov.cn/mz/upload/pub/load/resource_download.html?resourceid=ff80808162718ac7016275d0c49e002d',
               'http://cishan.chinanpo.gov.cn/mz/upload/pub/load/resource_download.html?resourceid=ff80808162719228016275c014f700dc',
               'http://cishan.chinanpo.gov.cn/mz/upload/pub/load/resource_download.html?resourceid=ff80808162719228016275a2d33d00c6',
               'http://cishan.chinanpo.gov.cn/mz/upload/pub/load/resource_download.html?resourceid=ff8080816271922801627551a95d00af',
               'http://cishan.chinanpo.gov.cn/mz/upload/pub/load/resource_download.html?resourceid=ff80808162719228016274eb5c5300a3',
               'http://cishan.chinanpo.gov.cn/mz/upload/pub/load/resource_download.html?resourceid=ff8080816271922801627453688d000d'],
 'files': []}
2018-04-02 17:14:47 [scrapy.core.engine] INFO: Closing spider (finished)
2018-04-02 17:14:47 [scrapy.statscollectors] INFO: Dumping Scrapy stats:
{'downloader/request_bytes': 518,
 'downloader/request_count': 1,
 'downloader/request_method_count/GET': 1,
 'downloader/response_bytes': 12444,
 'downloader/response_count': 1,
 'downloader/response_status_count/200': 1,
 'finish_reason': 'finished',
 'finish_time': datetime.datetime(2018, 4, 2, 9, 14, 47, 11611),
 'item_scraped_count': 1,
 'log_count/DEBUG': 3,
 'log_count/INFO': 7,
 'response_received_count': 1,
 'scheduler/dequeued': 1,
 'scheduler/dequeued/memory': 1,
 'scheduler/enqueued': 1,
 'scheduler/enqueued/memory': 1,
 'start_time': datetime.datetime(2018, 4, 2, 9, 14, 46, 433082)}
2018-04-02 17:14:47 [scrapy.core.engine] INFO: Spider closed (finished)

下载链接都有了，但是好像没有启动下载，请问为什么？