How to return 404 with Spring WebFlux -

i'm having controller 1 (in kotlin):

@restcontroller @requestmapping("/") class customercontroller (private val service: customerservice) {     @getmapping("/{id}")     fun findbyid(@pathvariable id: string,                  @requestheader(value = if_none_match) versionheader: string?): mono<httpentity<kunderesource>> =         return service.findbyid(id)             .switchifempty(mono.error(notfoundexception()))             .map {                 // etag stuff ...                 ok().etag("...").body(...)             } } 

im wondering whether there better approach throwing exception annotated @responsestatus(code = not_found)

i lie use routefunction instead of @restcontroller when spring 5 stable. define handlerfunction handle request, , declare routefunction map request handlerfunction:

public mono<serverresponse> get(serverrequest req) {     return this.posts         .findbyid(req.pathvariable("id"))         .flatmap((post) -> serverresponse.ok().body(mono.just(post), post.class))         .switchifempty(serverresponse.notfound().build()); } 

kotlin version, , use routefunctiondsl map incoming request handlerfuncation:

fun get(req: serverrequest): mono<serverresponse> {     return this.posts.findbyid(req.pathvariable("id"))             .flatmap { post -> ok().body(mono.just(post), post::class.java) }             .switchifempty(notfound().build()) } 

it can expression, like:

fun get(req: serverrequest): mono<serverresponse> = this.posts.findbyid(req.pathvariable("id"))             .flatmap { post -> ok().body(mono.just(post), post::class.java) }             .switchifempty(notfound().build())