Spring Webflux Mono is ignoring ResponseEntity's status and returning 200 OK - kotlin

Question

I have a RestController which looks like this
#RestController
#RequestMapping("/user")
class UserController(val userService: UserService) {
#PostMapping("/register")
fun register(#RequestBody body: UsernamePasswordResource): Mono<*> {
return userService.createUser(body.username, body.password)
.map {ResponseEntity(it, HttpStatus.CREATED)}
.doOnError {
if (it is DuplicateUserException){
ResponseEntity(ErrorResource(it.message!!), HttpStatus.BAD_REQUEST)
} else {
ResponseEntity(ErrorResource("Internal server error"), HttpStatus.INTERNAL_SERVER_ERROR)
}
}
}
}
When I create a using using this endpoint 200 OK in response and this as body:
{
"headers": {},
"body": {
"username": "test7",
"passwordEncoded": "4HxMMUI09pltEr9pyKIxsQ==",
"description": ""
},
"statusCode": "CREATED",
"statusCodeValue": 201
}
Why is the status of my ResponseEntity ignored and 200 is returned? How do i fix this? Thanks in advance.

Answer 1

Spring provides an HTTP 200 (OK) response by default when an endpoint returns successfully. To return a custom HTTP status, use the #ReponseStatus annotation above your function and pass your status code in the parenthesis. Your code snippet should look like:
#RestController
#RequestMapping("/user")
class UserController(val userService: UserService) {
#PostMapping("/register")
#ResponseStatus(HttpStatus.CREATED)
fun register(#RequestBody body: UsernamePasswordResource): Mono<*> {
return userService.createUser(body.username, body.password)
.map {ResponseEntity(it, HttpStatus.CREATED)}
.doOnError {
if (it is DuplicateUserException){
ResponseEntity(ErrorResource(it.message!!), HttpStatus.BAD_REQUEST)
} else {
ResponseEntity(ErrorResource("Internal server error"), HttpStatus.INTERNAL_SERVER_ERROR)
}
}
}
}

Answer 2

I figured it out. The endpoint was returning Mono<*>
After I changed my service to return AuthenticationResource instead of UserResource
I could also make the endpoint return Mono<ResponseEntity<AuthenticationResource>>.
After that the ResponseEntity was respected and used as normal.