Http response codes for invalid data and data conflict

Question

Possible Duplicate:
REST response code for invalid data

Have the following REST resource:

POST /user/{primary_key}

The resource is intended to work like an "ADD/UPDATE" operation. This means that it can be used to:

Create a new user
Update information on an existing user

If a client wanted to create a new user, some information is required:

POST user/{pimary_key}
Paylod:
 - Username - (must be unique)
 - Password

If a client wants to simply update an existing user, the call only needs to include the primary key and the new/changed information. For example:

POST user/{pimary_key}
Paylod:
 - favorite hamburger type

This situation creates the potential for several requests from the client that are invalid:

CONFLICT - The client updates an existing user attempting to change the username to a value that is already in use by a different user.
MISSING INFORMATION - The client attempts to create a new user without including necessary information such as the username and password.

What are the correct HTTP response codes to return in these cases?

Thanks so much!

score 13 · Accepted Answer · answered Jan 02 '13 at 19:33

13

code 201 for created user, quite obvious
400 for incorrect input parameters is the most suitable, google API uses it
seems 409 the best for conflicting situation like yours

I would only recommend to separate creation and editing, and use different methods for them - POST to create, PUT to update. What if the user was going to modify something, but had a typo? It is better to show an error

answered Jan 02 '13 at 19:33

allergic

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Good point on the `POST` vs `PUT` recommendation. – Marco Roy Dec 29 '15 at 23:43

score 6 · Answer 2 · answered Jan 02 '13 at 18:51

Here's a good table of "typical" HTTP responses to RESTful operations.

From that table, here's what's recommended for POST operations:

200 (OK) - if an existing resource has been updated
201 (created) - if a new resource is created
202 (accepted) - accepted for processing but not been completed (Async processing)

301 (Moved Permanently) - the resource URI has been updated
303 (See Other) - e.g. load balancing

400 (bad request) - indicates a bad request
404 (not found) - the resource does not exits
406 (not acceptable) - the server does not support the required representation
409 (conflict) - general conflict     
412 (Precondition Failed) e.g. conflict by performing conditional update
415 (unsupported media type) - received representation is not supported

500 (internal server error) - generic error response
503 (Service Unavailable) - The server is currently unable to handle the request

Http response codes for invalid data and data conflict

2 Answers2