What HTTP return code in the request for empty result 204 or 404?

Question

I have a call with a return object, but this call may return an empty result.

My URL in controller is:

/api/find-by-id/{id}

This controller make calls service as the following:

service.findById(Integer id);

My sevice searches through DAO:

repository.findById(Integer id); 

When DAO return an empty value, should I send error HTTP 404 or HTTP 204 to front?

Considering:

• 2xx: Success - The action was successfully received, understood, and accepted

• 4xx: Client Error - The request contains bad syntax or cannot be fulfilled

HTTP 204: Means that something was found, but it's empty.

HTTP 404: Not found.

Answer 1

If your findById always returns exactly 0 or 1 items, and this is your request:

GET /api/find-by-id/{id}

Then I believe that the result should be 404 if an item does not exist.

204 is different. It doesn't really imply an item doesn't exist, it implies that the operation was a success, but the result is empty + a hypermedia client should not refresh the current view. It's rarely used as a response to GET request because it doesn't make that much sense.

Since it sounds like you're using a database, the equivalent to 204 / empty would be a database record with that id, but all the fields are null. The equivalent to 404 would be that the database record does not exist at all.