Spring webflux: ServerResponse redirection - spring-boot

Question

This is my related code:
#RestController
public class GicarController {
#PostMapping("/login")
public Mono<ServerResponse> gicar(#RequestHeader("GICAR_ID") String gicarId) {
return ServerResponse.temporaryRedirect(URI.create("/me")).build();
}
}
Issue arises when I'm calling to _/login endpoint:
$ curl -i -X POST localhost:8080/login -H "GICAR_ID: tre"
HTTP/1.1 200 OK
transfer-encoding: chunked
Content-Type: text/event-stream;charset=UTF-8
Cache-Control: no-cache, no-store, max-age=0, must-revalidate
Pragma: no-cache
Expires: 0
X-Content-Type-Options: nosniff
X-Frame-Options: DENY
X-XSS-Protection: 1 ; mode=block
Referrer-Policy: no-referrer
curl: (18) transfer closed with outstanding read data remaining
Why am I getting an 200 http code response?
On spring boot logging I'm getting this exception:
022-06-27 13:11:19.931 ERROR 79654 --- [or-http-epoll-2] r.n.http.server.HttpServerOperations : [9750a9d8-1, L:/127.0.0.1:8080 - R:/127.0.0.1:33150] Error finishing response. Closing connection
org.springframework.core.codec.CodecException: Type definition error: [simple type, class org.springframework.web.reactive.function.server.DefaultServerResponseBuilder$WriterFunctionResponse]; nested exception is com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class org.springframework.web.reactive.function.server.DefaultServerResponseBuilder$WriterFunctionResponse and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS)
Why above exception is reaised?
Any ideas?

Answer 1

According to Spring documentation ServerResponse
Represents a typed server-side HTTP response, as returned by a handler function or filter function.
and it supposed to be used in Functional Endpoints
#Configuration
public class GicarConfiguration {
#Bean
public RouterFunction<ServerResponse> route() {
return RouterFunctions
.route(POST("/login"), this::loginHandler);
}
private Mono<ServerResponse> loginHandler(ServerRequest request) {
var gicarId = request.headers().firstHeader("GICAR_ID");
return ServerResponse.temporaryRedirect(URI.create("/me")).build();
}
}
If you still want to use Annotated Controllers, use ResponseEntity instead
#RestController
public class GicarController {
#PostMapping("/login")
public Mono<ResponseEntity<Void>> gicar() {
return Mono.just(ResponseEntity
.status(HttpStatus.TEMPORARY_REDIRECT)
.header(HttpHeaders.LOCATION, "/me")
.build()
);
}
}