如果发布子资源时资源不存在，则在REST API中使用哪个HTTP状态代码？

Question

To create a document for a project in an REST API,

POST /projects/1234/documents

What status is expected to return if the project with id=1234 doesn't exist?

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Related to this question , but dealing with POSTs, not GETs.

Answer 1

Short answer: for most use cases similar to what you describe, 404.

More completely: the notion of "subresource" doesn't really exist in HTTP.

Yes, URI have a standard hierarchy of segments, and you can use relative resolution of dot segments to compute one URI from another. Those semantics do not translate into a hierarchy of resources.

/projects/1234/documents isn't a description of a path traversal, it's a key into a dictionary.

As far as HTTP is concerned, it is perfectly fine that /projects/1234/documents exists even though /projects and /projects/1234 do not.

Put slightly differently, the metadata in your response, which includes the status code, apply to the /projects/1234/documents resource, and not anything else .

Note that this goes both directions: not only does /projects/1234/documents not imply anything about /projects/1234 , but it is also the case that it doesn't imply anything about /projects/1234/documents/5678 .

Your best reference for getting your head around this is still going to be Fielding's thesis . It may also help to review RFC 7234