scrapy中下载器中间件(Downloader Middleware)的顺序问题？

默认：

{
    'scrapy.contrib.downloadermiddleware.robotstxt.RobotsTxtMiddleware': 100,
    'scrapy.contrib.downloadermiddleware.httpauth.HttpAuthMiddleware': 300,
    'scrapy.contrib.downloadermiddleware.downloadtimeout.DownloadTimeoutMiddleware': 350,
    'scrapy.contrib.downloadermiddleware.useragent.UserAgentMiddleware': 400,
    'scrapy.contrib.downloadermiddleware.retry.RetryMiddleware': 500,
    'scrapy.contrib.downloadermiddleware.defaultheaders.DefaultHeadersMiddleware': 550,
    'scrapy.contrib.downloadermiddleware.redirect.MetaRefreshMiddleware': 580,
    'scrapy.contrib.downloadermiddleware.httpcompression.HttpCompressionMiddleware': 590,
    'scrapy.contrib.downloadermiddleware.redirect.RedirectMiddleware': 600,
    'scrapy.contrib.downloadermiddleware.cookies.CookiesMiddleware': 700,
    'scrapy.contrib.downloadermiddleware.httpproxy.HttpProxyMiddleware': 750,
    'scrapy.contrib.downloadermiddleware.chunked.ChunkedTransferMiddleware': 830,
    'scrapy.contrib.downloadermiddleware.stats.DownloaderStats': 850,
    'scrapy.contrib.downloadermiddleware.httpcache.HttpCacheMiddleware': 900,
}


我如何激活自己的下载中间件(如何设置顺序，见下面的问号)?
    DOWNLOADER_MIDDLEWARES = {
    'scrapy.contrib.downloadermiddleware.redirect.RedirectMiddleware': ?,
    'MyProject_XXX.middlewares.RedirectMiddleware': ?,
}

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数字越小的中间件越靠近引擎，数字越大的中间件越靠近下载器

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你是要用自己写的重定向中间件取代原有的么？ 那原有的中间件顺序设为 None 。自己写的取代原有顺序就行了咯。 或者结合自己的业务逻辑来考虑。