Hi Mark,
> -----Original Message-----
> From: Mark Thomas [mailto:[email protected]]
> Sent: Saturday, July 29, 2017 2:56 PM
>
>> (...)
>>
> >Why would Tomcat want to modify static files, instead of just serving
> >them as-is?
>
> Because Tomcat now checks the response encoding and the file encoding
> and converts if necessary.
>
> You probably want to set the fileEncoding init param of the Default servlet to
> UTF-8.
Thanks. So I set the following parameter in web.xml:
<init-param>
<param-name>fileEncoding</param-name>
<param-value>utf-8</param-value>
</init-param>
The result now is, that Tomcat converts the static file without a BOM from
UTF-8 to ISO-8859-1, which means my JavaScript files included by the HTML page
will still be broken, as the brower expects them to be UTF-8-encoded ...
I honestly don't understand that change. As a web developer, I expect a web
server to serve static files exactly as-is, without trying to convert the files
into another charset and without trying to detect the charset of the file
(unless the server is configured to do so).
Bug 49464 [1] mentions that "As per spec the encoding of the page is asssumed
to be iso-8859-1.". Do I understand correctly that this refers to the following
section "3.7.1 Canonicalization and Text Defaults" of RFC2616?
(...)
The "charset" parameter is used with some media types to define the
character set (section 3.4) of the data. When no explicit charset
parameter is provided by the sender, media subtypes of the "text"
type are defined to have a default charset value of "ISO-8859-1" when
received via HTTP.
But not that RFC7231 says in "Appendix B. Changes from RFC 2616":
The default charset of ISO-8859-1 for text media types has been
removed; the default is now whatever the media type definition says.
Likewise, special treatment of ISO-8859-1 has been removed from the
Accept-Charset header field. (Section 3.1.1.3 and Section 5.3.3)
I found a following page that talks about this change [2] and mentions RFC6657
[3] that describes text/* media registrations with charset handling.
While RFC6657 seems to indicate that the default charset of text/plain is
US-ASCII (which is not what browsers do), it doesn't seem to indicate a default
charset for other types like text/html, text/javascript, application/javascript
etc.
Browsers (I tested with IE, Firefox and Chrome) already handle the encoding of
text-based files where the Content-Type doesn't specify a charset as the user
would expect:
- For example, with text/html files that don't contain a BOM, they will respect
the <meta charset=...> element. If a UTF-8 BOM is present, they will interpret
it as UTF-8.
- If you directly open text/plain, text/css, application/javascript files in a
browser, they will check if the file has an UTF-8 BOM, and interpret it as
UTF-8 in that case; otherwise, they seem to interpret it as
ISO-8859-1/Windows-1252 (or maybe using the default system encoding, I'm not
exactly sure about that).
- However, if such files (.css and .js) are referenced by a HTML file, browsers
will interpret them in the same encoding that the HTML file (if they don't have
a BOM), which means if the HTML uses UTF-8, they will interpret .js and .css
also as UTF-8 (unless the HTML element uses a charset parameter, e.g. <script
src="script.js" charset="windows-1252"></script>).
Therefore, I don't see why Tomcat would want to convert static resources to
other encodings. (I think it should also not try to detect the charset of files
and then include a "; charset=..." parameter in the Content-Type, as this may
override the browser's behavior and thus also lead to incorrect decoding of
JavaScript files that are encoded with UTF-8 without a BOM).
Further, as an system administrator, I would expect that I can update Tomcat
from x.y.z to x.y.(z+n), without static JavaScript files suddenly getting
broken (which isn't immediately obvious as mostly the script per se will work,
only that some special string characters outside of ASCII are displayed
incorrectly to the user).
Shouldn't such behavior changes be reserved for the next major/minor version
which is not yet stable, in this case Tomcat 9.0.0?
Thanks!
Regards,
Konstantin Preißer
[1] https://bz.apache.org/bugzilla/show_bug.cgi?id=49464
[2] https://github.com/requests/requests/issues/2086
[3] https://tools.ietf.org/html/rfc6657
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