How can I convert a Stream of Mono to Flux

问题

I have a method that try use WebClient to return a Mono

    @GetMapping("getMatch")
    public Mono<Object> getMatch(@RequestParam Long matchId) {
        return WebClient.create(OpenDotaConstant.BASE_URL).get()
                .uri("/matches/{matchId}", matchId)
                .accept(MediaType.APPLICATION_JSON)
                .retrieve()
                .bodyToMono(Object.class);

    }

It can return result that I expected. Then I try to create another method to support List as params

    @GetMapping("getMatches")
    public Flux<Object> getMatches(@RequestParam String matchesId) {
        List<Long> matchesList = JSON.parseArray(matchesId, Long.class);

        return Flux.fromStream(matchesList.parallelStream().map(this::getMatch));
    }

But this time return a weird result.

[
    {
        "scanAvailable": true
    },
    {
        "scanAvailable": true
    }
]

I'm new to reactive-programming, What is the correct way to combine Stream and Mono,and then convert to the Flux?

回答1:

Probably, what you need is the following:

@GetMapping("getMatches")
public Flux<Object> getMatches(@RequestParam String matchesId) {
    List<Long> matchesList = JSON.parseArray(matchesId, Long.class);
    return Flux.fromStream(matchesList.stream())
               .flatMap(this::getMatch);
}

Instead of:

@GetMapping("getMatches")
public Flux<Object> getMatches(@RequestParam String matchesId) {
    List<Long> matchesList = JSON.parseArray(matchesId, Long.class);
    return Flux.fromStream(matchesList.parallelStream().map(this::getMatch));
}

Notes:

Basically, you expect getMatches endpoint to return Flux<Object>. However, as it is written - it actually returns Flux<Mono<Object>>, therefore you see the strange output. To get Flux<Object>, I suggest, first, create Flux<Long> that are match ids, and then flatMap the result of calling getMatch (that returns Mono<Object>), this finally gives Flux<Object>.
Also, there is no need to use parallelStream(). Because you're already using reactor, everything will be performed concurrently on reactor scheduler.

来源：https://stackoverflow.com/questions/58153574/how-can-i-convert-a-stream-of-mono-to-flux

标签

spring-webflux