Does anyone know how I can let my Spring controller return a 404? I thought I could just return a nu...

# spring

[Kaj]

Does anyone know how I can let my Spring controller return a 404? I thought I could just return a nullable variable and if it is null Spring would translate it to a 404. Do I really need to use ResponseEntity specifically?

[nfrankel]

how does spring knows what null means?
it could mean a 500
or anything...
you’ve to set the http response code specifically

[Kaj]

Okay, I thought there would be a shortcut because in Java with the @RestController a GetMapping that calls the repo and returns nothing aka null it returns a 404

[nfrankel]

really?
seems strange
https://stackoverflow.com/questions/25422255/how-to-return-404-response-status-in-spring-boot-responsebody-method-return-t/25422563
(by the way, this is not kotlin specific)

[Daniel Selinger]

i was just about to say that

[Daniel Selinger]

i've seen most projects do it with NotFoundException

[Daniel Selinger]

which imo is fugly

[Daniel Selinger]

also a lot of projects do this for a gazillion of other errors with a global exception handler

[fabricio]

you can annotate with

@ResponseStatus(HttpStatus.NOT_FOUND)

or you can

return ResponseEntity.notFound()

[isto]

I'd recommend writing a @ControllerAdvice to handle exceptions in a uniform way (example https://github.com/istonikula/realworld-api/blob/master/realworld-app/web/src/main/kotlin/io/realworld/ErrorHandler.kt), keeping your domain independent of the framework used and communicate domain errors with explicit types (example https://github.com/istonikula/realworld-api/blob/master/realworld-domain/src/main/kotlin/io/realworld/domain/core/Users.kt), then convert and forward the domain errors as exceptions in the adapter (in this case the rest api controller https://github.com/istonikula/realworld-api/blob/master/realworld-app/web/src/main/kotlin/io/realworld/Users.kt), so both the unexpected and expected cases will be serialized in the same place