scrapy 响应文本乱码(不支持Brotli解压)

一.介绍

　　在scrapy中，默认不支持Brotli解压，当发现响应乱码时，如何分析确定是由Brotli压缩引起的呢？

　　　　1）是看请求头是否有'Accept-Encoding': "gzip, deflate, br" 中的br，如果去掉br 再请求网页，如果响应不成功，则表示服务端只支持br压缩格式，如果成功则看是否乱码。

　　　　2)  添加中间件调试查看，使用的是哪种压缩格式，关键代码如下

    custom_settings = {
        'DOWNLOADER_MIDDLEWARES':{
            #加上中间件，主要用于查看是什么类型的压缩
            'realtime_python_crawler.middlewares_custom.myCompression_dm.myHtmlCompression':500
            }
　　　　　}

　　　　在创建一个myCompression_dm.py文件，在return时打入断点调试进去

from scrapy.downloadermiddlewares.httpcompression import HttpCompressionMiddleware    

class myHtmlCompression(HttpCompressionMiddleware):

    def process_response(self, request, response, spider):
       return super().process_response(request, response, spider)

　　　　HttpCompressionMiddleware中间件中源码中解缩代码如下：　

    def _decode(self, body, encoding):
        if encoding == b"gzip" or encoding == b"x-gzip":
            body = gunzip(body)

        if encoding == b"deflate":
            try:
                body = zlib.decompress(body)
            except zlib.error:
                # ugly hack to work with raw deflate content that may
                # be sent by microsoft servers. For more information, see:
                # http://carsten.codimi.de/gzip.yaws/
                # http://www.port80software.com/200ok/archive/2005/10/31/868.aspx
                # http://www.gzip.org/zlib/zlib_faq.html#faq38
                body = zlib.decompress(body, -15)
        if encoding == b"br" and b"br" in ACCEPTED_ENCODINGS:
            body = brotli.decompress(body)
        if encoding == b"zstd" and b"zstd" in ACCEPTED_ENCODINGS:
            # Using its streaming API since its simple API could handle only cases
            # where there is content size data embedded in the frame
            reader = zstandard.ZstdDecompressor().stream_reader(io.BytesIO(body))
            body = reader.read()
        return body

　　解决方法，如果确定是br压缩格式引起的，就安装pip install Brotli， 这样响应就不会乱码