Adding custom Response header to Spring WebFlux contoller endpoint - spring-webflux

Question

Is there a way to add a response header to spring webflux controller endpoint? for example to the following method I have to add a custom header say 'x-my-header'
#GetMapping(value = "/search/{text}")
#ResponseStatus(value = HttpStatus.OK)
public Flux<SearchResult> search(#PathVariable(
value = "text") String text){
return searchService().find(text);
}

Answer 1

In the functional API, this is really easy; the ServerResponse builder has builders for almost everything you need.
With the annotated controllers; you can return an ResponseEntity<Flux<T>> and set the headers:
#GetMapping(value = "/search/{text}")
public ResponseEntity<Flux<SearchResult>> search(#PathVariable(
value = "text") String text) {
Flux<SearchResult> results = searchService().find(text);
return ResponseEntity.ok()
.header("headername", "headervalue")
.body(results);
}
Note that the updated code doesn't need the #ResponseStatus annotation now.
UPDATE:
Apparently the solution above works; unless you have spring-cloud-starter-netflix-hystrix-dashboard dependency. In that case you can use the following code:
#GetMapping(value = "/search/{text}")
public Mono<ResponseEntity<List<SearchResult>>> search(#PathVariable(
value = "text") String text) {
return searchService().find(text)
.collectList()
.map(list -> ResponseEntity.ok()
.header("Header-Name", "headervalue")
.body(list));
}
A couple of things to note:
Outer type should be Mono<ResponseEntity<T>>: There is one response for request. If you declare it to be a Flux, Spring will try to deserialize the ResponseEntity as if it was a POJO.
You need to use an operator to transform the Flux into a Mono: collectList() or single() will do the job for you.
Checked with Spring Boot 2.0.3.RELEASE