REST, HTTP DELETE and parameters
It's an old question, but here are some comments...
- In SQL, the DELETE command accepts a parameter "CASCADE", which allows you to specify that dependent objects should also be deleted. This is an example of a DELETE parameter that makes sense, but 'man rm' could provide others. How would these cases possibly be implemented in REST/HTTP without a parameter?
- @Jan, it seems to be a well-established convention that the path part of the URL identifies a resource, whereas the querystring does not (at least not necessarily). Examples abound: getting the same resource but in a different format, getting specific fields of a resource, etc. If we consider the querystring as part of the resource identifier, it is impossible to have a concept of "different views of the same resource" without turning to non-RESTful mechanisms such as HTTP content negotiation (which can be undesirable for many reasons).
No, it is not RESTful. The only reason why you should be putting a verb (force_delete) into the URI is if you would need to overload GET/POST methods in an environment where PUT/DELETE methods are not available. Judging from your use of the DELETE method, this is not the case.
HTTP error code 409/Conflict should be used for situations where there is a conflict which prevents the RESTful service to perform the operation, but there is still a chance that the user might be able to resolve the conflict himself. A pre-deletion confirmation (where there are no real conflicts which would prevent deletion) is not a conflict per se, as nothing prevents the API from performing the requested operation.
As Alex said (I don't know who downvoted him, he is correct), this should be handled in the UI, because a RESTful service as such just processes requests and should be therefore stateless (i.e. it must not rely on confirmations by holding any server-side information about of a request).
Two examples how to do this in UI would be to:
- pre-HTML5:* show a JS confirmation dialog to the user, and send the request only if the user confirms it
- HTML5:* use a form with action DELETE where the form would contain only "Confirm" and "Cancel" buttons ("Confirm" would be the submit button)
(*) Please note that HTML versions prior to 5 do not support PUT and DELETE HTTP methods natively, however most modern browsers can do these two methods via AJAX calls. See this thread for details about cross-browser support.
Update (based on additional investigation and discussions):
The scenario where the service would require the force_delete=true flag to be present violates the uniform interface as defined in Roy Fielding's dissertation. Also, as per HTTP RFC, the DELETE method may be overridden on the origin server (client), implying that this is not done on the target server (service).
So once the service receives a DELETE request, it should process it without needing any additional confirmation (regardless if the service actually performs the operation).
I think this is non-restful. I do not think the restful service should handle the requirement of forcing the user to confirm a delete. I would handle this in the UI.
Does specifying force_delete=true make sense if this were a program's API? If someone was writing a script to delete this resource, would you want to force them to specify force_delete=true to actually delete the resource?