GET request with "If-Match" and ETags

Question

I'm working on implmenenting ETag functionality for a RESTful service, and I'd like to be as close to the HTTP spec as possible. The spec however is not as clear as it probably should be. Specifically:

The If-Match header - what are it's semantics for a GET request?

Presumably, a GET with the If-Match header will, if the value is matched with the value of the ETag - return the actual Resource with 200 OK (not 304). If the value is not matched, a 412 Precondition Failed should be returned, along with the new value of the ETag and no content?

Answer 1

That's correct, expect that the new value of the ETag on a 412 response to a If-Match is nowhere required by the spec. You can omit it. It's only recommended on a 304 response to a If-None-Match. Perhaps that's where your confusion was caused.