Why webClient doesn't do any http call?

问题

I have following code:

 List<Mono<MyResponseDTO>> monoList = queue.stream()
                .map(jobStatusBunch -> webClient
                        .post()
                        .uri("localhost:8080/api/some/url")
                        .bodyValue(convertToRequestDto(someBean))
                        .retrieve()
                        .toEntity(String.class)
                        .filter(HttpEntity::hasBody)
                        .map(stringResponseEntity -> {
                            try {
                                return objectMapper.readValue(stringResponseEntity.getBody(), MyResponseDTO.class);
                            } catch (JsonProcessingException e) {
                                log.error("Can't parse", e);
                                return null;
                            }
                        })
                        .doOnNext(myResponseDTO -> {
                            log.info("doOnNext is invoked");
                        })
                ).collect(Collectors.toList());
        //await when all MONOs are completed
        Mono<Void> mono = Flux.fromIterable(monoList).then();
        mono.subscribe(aVoid -> {
            log.info("!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!");
        });

webClient instantiantion:

this.webClient = WebClient.builder().build();

My aim allow to execute all http requests from queue in parallel and await when all of them are finished. But despite the fact that queue is not empty actual http call is not happen. Could you explain why and how to fix it?

UPDATE

Thanks @caco3 for advice. I corrected code like this:

log.info("Start waiting for {}", monoList);
Mono<Void> mono = Flux.fromIterable(monoList)
        .flatMap(Function.identity())
        .then();
log.info("Finished waiting for {}", monoList);

and I see following log:

2019-11-19 19:17:17.733  INFO 5896 --- [   scheduling-1] c.b.m.service.MyService     : Start waiting for [MonoPeek]
2019-11-19 19:17:25.988  INFO 5896 --- [   scheduling-1] c.b.m.service.MyService     : Finished waiting for [MonoPeek]
2019-11-19 19:17:26.015 TRACE 5896 --- [   scheduling-1] o.s.w.r.f.client.ExchangeFunctions       : [c42c1c2] HTTP POST localhost:8080/api/some/url, headers={}
2019-11-19 19:17:48.230  INFO 5896 --- [tor-http-nio-11] c.b.m.service.MyService     : doOnNext is invoked

So current code doesn't await all reqests termination.But I really need it

来源：https://stackoverflow.com/questions/58937713/why-webclient-doesnt-do-any-http-call