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https://issues.apache.org/jira/browse/TIKA-539?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12932103#action_12932103
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Andrzej Bialecki commented on TIKA-539:
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I'm not sure what mechanism Tika uses. Nutch collects a list of clues, which
come from protocol headers, html meta "sniffing" (there's a chicken and egg
issue here, so it's at most a best effort attempt) and from ICU4j
CharsetDetector, and then tries to pick the one with the greatest level of
confidence. Clues from ICU are given a higher priority, so they win if they are
present. After that the next candidate is the protocol header information, and
finally the "sniffed" HTML meta encoding. The final encoding is also checked
against Charset.isSupported and rejected if this returns false.
> Encoding detection is too biased by encoding in meta tag
> --------------------------------------------------------
>
> Key: TIKA-539
> URL: https://issues.apache.org/jira/browse/TIKA-539
> Project: Tika
> Issue Type: Bug
> Components: metadata, parser
> Affects Versions: 0.8
> Reporter: Reinhard Schwab
> Assignee: Ken Krugler
> Fix For: 0.9
>
> Attachments: TIKA-539.patch, TIKA-539_2.patch
>
>
> if the encoding in the meta tag is wrong, this encoding is detected,
> even if there is the right encoding set in metadata before(which can be from
> http response header).
> test code to reproduce:
> static String content = "<html><head>\n"
> + "<meta http-equiv=\"content-type\"
> content=\"application/xhtml+xml; charset=iso-8859-1\" />"
> + "</head><body>Über den Wolken\n</body></html>";
> /**
> * @param args
> * @throws IOException
> * @throws TikaException
> * @throws SAXException
> */
> public static void main(String[] args) throws IOException, SAXException,
> TikaException {
> Metadata metadata = new Metadata();
> metadata.set(Metadata.CONTENT_TYPE, "text/html");
> metadata.set(Metadata.CONTENT_ENCODING, "UTF-8");
> System.out.println(metadata.get(Metadata.CONTENT_ENCODING));
> InputStream in = new
> ByteArrayInputStream(content.getBytes("UTF-8"));
> AutoDetectParser parser = new AutoDetectParser();
> BodyContentHandler h = new BodyContentHandler(10000);
> parser.parse(in, h, metadata, new ParseContext());
> System.out.print(h.toString());
> System.out.println(metadata.get(Metadata.CONTENT_ENCODING));
> }
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