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https://issues.apache.org/jira/browse/NUTCH-3089?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17898303#comment-17898303
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Tim Allison commented on NUTCH-3089:
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Thank you [~snagel]! If {{mime.type.magic}} doesn't already exist, I'm
wondering if we can modify it so something like {{mime.type.detect}}. The
(admittedly pedantic) difference is that Tika uses magic but also has container
detection (if tika-parsers-standard is on the class path).
> Review MIME type detection
> --------------------------
>
> Key: NUTCH-3089
> URL: https://issues.apache.org/jira/browse/NUTCH-3089
> Project: Nutch
> Issue Type: Improvement
> Components: protocol, util
> Affects Versions: 1.20
> Reporter: Sebastian Nagel
> Priority: Major
> Fix For: 1.21
>
>
> The MIME detection in {{o.a.n.util.MimeUtil#autoResolveContentType}} needs a
> review:
> - the fall-back to use the Content-Type HTTP header, only moderately cleaned,
> leads to strange-looking and obviously misspelled resp. invalid MIME types:
> "application/.octet-stream", "application/."
> - note: this issue stems from a [discussion on the Common Crawl user
> group|https://groups.google.com/g/common-crawl/c/0FANtRcJOts/m/q5KtncIcBgAJ].
> More examples are given there.
> - Tika's method
> [MimeTypes#forName|https://tika.apache.org/3.0.0/api/org/apache/tika/mime/MimeTypes.html#forName(java.lang.String)]
> used in [MimeUtil.java, line
> 162|https://github.com/apache/nutch/blob/e1b8dbe909b0f8c181dcb5ee0e7e072f27f82cbb/src/java/org/apache/nutch/util/MimeUtil.java#L162]
> does only a limited validation, not sufficient to filter out the above
> mentioned erroneous MIME types.
> - performance: if the property {{mime.type.magic}} == true, Tika's magic
> detector is called with the binary content and the URL (which includes the
> file suffix) and the Content-Type HTTP header as additional hints to support
> the detection. Tika's detect method uses similar fall-back heuristics,
> calling also {{MimeTypes#forName}}. Relying only on Tika's detect method if
> {{mime.type.magic}} == true, should save computation time, and eventually
> leads to more precise results.
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