RESTful way to check availability of usernames, emails, etc

Question

I've recently gotten very into trying to think as RESTfully as possible, and I'm finding myself stymied by the non-obvious routes.

In this particular case, I'm curious about the RESTful way to check for username and email availability for a user, or anything else that has uniqueness.

My gut tells me that I would want to perform a GET on /users/email or /users/username/ each with a required param, or something along the lines of GET /users/search/ with optional params of email and username. If you get a 200, then the username or email is unavailable; if you get a 404, then it's available.

I prefer the first option since it's more explicit, but it's not like I've pored over Roy Fielding's thesis to know well enough what to do.

What's the most sound approach here?

Answer 1

The first approach does seem to be more "RESTful". You try to GET a specific resource (by username or email) and get it if it exists or get a status message "unavailable resource". This would be:

• GET /users/username/johnwayne (to "get" johnwayne resource/username availability...)

This should generate:

• 200: if resource exists
• 404: if the resource does not exist

The second one seems more like "SOAP"-like web service, where you define a "function" (/users/search/) with some "parameters" (username, email)...