what http response code for rest service on put method when domain rules invalid

Question

What is the most appropriate response code to return when using the PUT method to update a resource, and the request contains some data that would invalidate the domain rules?

For example, a customer resource must have a name specified. If an agent tries to issue a PUT without supplying a name I don't want to update the resource, and I want to tell the caller that they need to supply a name.

What HTTP response code?

Answer 1

The response code is not related to the http method in this case. You should return the same status code as if it had been a POST request. I'd say you should use 400 or 409 (Note: See further discussion of the difference between the two in the comments).

Answer 2

How about 422?

"The 422 (Unprocessable Entity) status code means the server understands the content type of the request entity (hence a 415(Unsupported Media Type) status code is inappropriate), and the syntax of the request entity is correct (thus a 400 (Bad Request) status code is inappropriate) but was unable to process the contained instructions. For example, this error condition may occur if an XML request body contains well-formed (i.e., syntactically correct), but semantically erroneous, XML instructions."

RFC 4918, Section 11.2

Answer 3

I would return a 400. Strictly, this is for "malformed syntax" (not invalid data), but in practice the YouTube, Twitter, etc. use it for more generally "bad" requests.