Question

I’m fairly familiar with REST principles, and have read the relevant dissertation, Wikipedia entry, a bunch of blog posts and StackOverflow questions on the subject, but still haven’t found a straightforward answer to a common case:

I need to request a resource to display. Depending on the resource’s state, I need to render either a read-only or an editable representation. In both cases, I need to GET the resource. How do I construct a URL to get the read-only or editable version?

If my user follows a link to GET /resource/<id>, that should suffice to indicate to me that s/he needs the read-only representation. But if I need to server up an editable form, what does that URL look like? GET /resource/<id>/edit is obvious, but it contains a verb in the URL. Changing that to GET /resource/<id>/editable solves that problem, but at a seemingly superficial level. Is that all there is to it — change verbs to adjectives?

If instead I use POST to retrieve the editable version, then how do I distinguish between the POST that initially retrieves it, vs the POST that saves it? My (weak) excuse for using POST would be that retrieving an editable version would cause a change of state on the server: locking the resource. But that only holds if my requirements are to implement such a lock, which is not always the case. PUT fails for the same reason, plus PUT is not enabled by default on the Web servers I’m running, so there are practical reasons not to use it (and DELETE).

Note that even in the editable state, I haven’t made any changes yet; presumably when I submit the resource to the Web server again, I’d POST it. But to get something that I can later POST, the server has to first serve up a particular representation.

I guess another approach would be to have separate resources at the collection level:
GET /read-only/resource/<id> and GET /editable/resource/<id> or GET /resource/read-only/<id> and GET /resource/editable/<id> … but that looks pretty ugly to me.

Thoughts?

Answer 1

1) It is perfectly valid to have two distinct resources, one for viewing and one for editing some domain concept. Just be aware that because they are two different URIs from REST’s perspective they are two different resources. Too often people conflate resource with domain object. That’s why they end up being stuck only doing CRUD.

2) Don’t get too hung up on the name of the resource. The important thing is that you realize that what the URI points to is a “thing”, “a resource”. If that’s more obvious to you with editable instead of edit then use that. Having a verb in your URL doesn’t make your application wrong, it just makes it a bit less readable to the human developer. Using a verb in the URL to try and redefine the semantics of the HTTP method, now that’s a violation of the uniform interface constraint.