Question

Assume I have a RESTful web service, which holds information about an object that can be accessed at an url like http://example.com/myobject. I would like to be able to retrieve this information in two formats: firstly, the XML-formatted plain data, and secondly, as a full HTML page, which may also include a javascript interface to change the object and PUT it back with AJAX.

What is the canonical way to achieve this? Should I publish my object at two different urls like http://example.com/myobject?format=xml and …format=html? (Are there better ways than using a query string to distinguish the URLS here?) Or is it sensible to send something like multipart MIME data and can I rely on browsers being able to extract the HTML part? Or is there some HTTP header field in the request I could use?

(With PUT or POST requests sent in different formats, it is much easier as the server can check the format and parse it accordingly.)

Answer 1

You could alternatively use content negotiation instead of querystring parameters. In a nutshell, the client sends the acceptable media types via the Accept header in the request (e.g. “application/xml, text/html;q=0.9”), and the server analyzes this and replies with the client-preferred media type (this process is called server-driven negotiation)

When doing server-driven negotiation, the response should contain a Vary header indicating what request header was used in the negotiation

Keep in mind that for this to work the client must send an appropriate Accept header.