It all depends on the Accept header that the client sends. For,
example Firefox (2.0.0.7) sends the Accept header: text/
xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/
plain;q=0.8,image/png,*/*;q=0.5. This can be interpreted as
text/xml: 100%
application/xml: 100%
application/xhtml+xml: 100%
image/png: 100%
text/html: 90%
text/plain: 80%
anything else (*/*): 50%
where the percentages are "quality" determinations <http://www.w3.org/
Protocols/rfc2616/rfc2616-sec14.html>--the higher the quality, the
more the client prefers it. As a result, if you declare that your
resource can be represented as both application/xml and text/html,
according to the above Accep header, you should be sending back XML.
I think Firefox is being forward-thinking with regard to XML and
XHTML, but not particularly practical here. (For example, IE cannot
handle pages served as application/xhtml+xml). (I don't have a
Windows machine in front of me, but I seem to remember that IE's
default Accept header is even less specific.)
You can get around this several ways (some better than others):
* using a client that allows custom headers (such as with an
XMLHttpRequest from within the browser)
* sniffing the requesting client and serving text/html to known browsers
* adding another request parameter to indicate the media-type,
overriding the accept headers (similar to RESTlet's support for
overriding the HTTP method to allow PUT)
For browser clients I just lean toward always serving text/html (and
perhaps text/plain), no matter what the Accept header says. Clients
that really do care about the server being able to send back
resources based on the Accept header will most likely allow for
custom headers anyway (e.g. Accept: application/xml,application/
json;q=0.9).
Here's what Jerome had to say last November: <http://
blog.noelios.com/2006/11/15/reconsidering-content-negotiation/>.
I'd be interested in hearing others' takes, though.
Justin
On Oct 10, 2007, at 10:50 AM, Sean Landis wrote:
When a request from a browser to a Restlet application is
processed, the
request will have many accepted media types. It appears that
Restlet scores
the accepted media types to prefer APPLICATION_XML and TEXT_XML
over TEXT_HTML.
This makes it difficult to have a resource support TEXT_HTML and
APPLICATION_XML as the resource cannot distinguish between requests
originating from a browser or a web service client in the case
where the
client is sending an XML representation such as via
JaxbRepresentation.
Are we misusing meida types? Or are the preferred scores correct?
It seems
a browser should prefer TEXT_HTML over any XML.
Thanks,
Sean
