In a HATEOAS API links are returned which represent possible state transitions. A conforming client should just be retrieving and following those links, but if a non-conforming client is constructing URIs rather than following the supplied links what would be the most appropriate status code/response to return?
- 400 would work, together with some information in the response body - this is what we're currently doing
- 403 I guess would be wrong, as it implies that the request could never work - but potentially the link may be available in the future
- 404 sounds plausible - at this point in time the resource doesn't exist
What do people think? I know that conditional requests can handle requests based on stale responses (resulting in e.g. 412s), but this is a slightly different situation.
OK, I see now that the correct response for these types of invalid operations would be a 404. How about where the syntax of a request is correct, it's going to a valid resource but it's somehow violating a business rule. Here's a couple of contrived examples:
- Let's say the client can provide two numbers which must be within 20% of each other, but otherwise could be any number.
- Let's say the client can provide a number which goes through some calculation the result of which indicates that the original number provided was incorrect.
Is 400 is the correct response for these?