[hunchentoot-devel] external-format and content-type question

[Hans Hübner]

Hi Bill,

Let me try to answer your question with a description of how external
formats in Hunchentoot are supposed to work.  I am talking about
Hunchentoot 1.2.0 specifically, as the behavior has changed since the
1.1 release family in the hope of making it easier to understand and
use.

External formats are meant to mostly work automatically.  It should be
enough to select a proper external format for the character set that
you normally use and set *hunchentoot-default-external-format* to
that.  The new default character set since 1.2.0 is :utf-8, so most
standard use cases should be covered.

Also new with 1.2.0 is Hunchentoot's ability to automatically report
the encoding used in replies sent.  This is done by adding a charset=
attribute to the reply content type, but only if the content type is a
subtype of "text" (i.e. it does not affect, say, application/xml).
This is independent of the *hunchentoot-default-external-format*
setting, i.e. you can set (reply-external-format*) in your handler to
something different from the default and still see the right charset
be added to the content-type, if it is text.

All this works for handlers that return strings, i.e. if you handler
returns an octet vector or directly writes to the response stream, you
are responsible for setting up the content-type in the reply properly
yourself.

If this does not work, please supply us with a specific case where and
how it does not.

Thanks!
Hans

On Thu, Nov 10, 2011 at 2:42 PM, Vassilis Radis <radisb at gmail.com> wrote:
> I recently had this problem:
> I use sbcl + hunchentoot (current quicklisp supplied version) to serve
> cl-who generated content that contains non-ascii range utf-8 chars (greek
> letters). Initially i got the usual encoding error while processing a
> request. So I found the  well known canonical solution: (setf
> *hunchentoot-default-external-format* (flex:make-external-format :utf8
> :eol-style :lf)). The result is that the browser (chrome) displayed garbage
> where the greek letters should appear, although i set the default encoding
> of chrome to UTF-8 and i include the utf-8 meta tag in the content. I saw in
> the chrome tools that hunchentoot sent Latin-1 Http content-type header.
> This showed me that I needed to send the content-type-header manually and
> that Chrome (correctly IMO) ignores the user setting for the default
> encoding, if it receives a different HTTP content-type type header. So I
> set *default-content-type* and all is well now. But I came across
> the (reply-external-format*) function which confused me.
> Now, i am trying to clarify the functional co-relation or/and overlapping
> between those three:
> 1.setting *hunchentoot-default-external-format*
> 2.setting (reply-external-format*)   --> is this just a per-request override
> of the *hunchentoot-default-external-format*?
> 3.sending the content-type header. --> Is there any legal scenario where we
> should report to the client something different than what is implied by
> (reply-external-format*)? What is the point of a default content-type header
> if there is a directly set default-external-format which also implicitly
> designates the header we should send?
> thanks in advance, Bill.
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