始终返回 HttpStatus 200（确定）

Question

We obtain a list of data from a SQL Server database. I want to return the list when there is data, but when there is not, I want to return a "No Content" status. My code:

public class Main {
  public static void main(String[] args) {
    var main = new Main();
    var result = main.controllerMethod();
    System.out.println("Result: " + result.blockingGet());
  }

  public Flowable<Person> personList(){
    List<Person> repositoryList = List.of();

    return repositoryList
        .stream()
        .collect(Collectors.collectingAndThen(Collectors.toList(), list -> {
          if(list.isEmpty()) return Flowable.empty();
          else return Flowable.fromIterable(list);
        }));
  }

  public Maybe<ResponseEntity<Flowable<Person>>> controllerMethod(){
    var httpStatus =
        new AtomicReference<>(HttpStatus.OK);

    return Maybe.just(personList()
        .switchIfEmpty(subs -> Completable.fromAction(() ->
                httpStatus.set(HttpStatus.NO_CONTENT)).toFlowable()))
        .map(person -> ResponseEntity.status(httpStatus.get())
            .body(person));
  }
}

result:

Result: <200 OK OK,io.reactivex.rxjava3.internal.operators.flowable.FlowableSwitchIfEmpty@35f983a6,[]>

Answer 1

It seems that you expect httpStatus.set(HttpStatus.NO_CONTENT) to be run, and after running, the status can be read with the correct statuscode. I'm not very familiar with reactive, but by looking at Completable.java I don't think the Action that you provide in Completable::fromAction is run right away.

There is probably a more reactive-like way to solve the problem, but I can't help you there. Instead, here's a solution that might work (or at least get you going in the right direction). Just set the value of the status explicitly yourself before returning your Flowable:

public Flowable<Person> personList(AtomicReference<HttpStatus> reference) {
    List<Person> repositoryList = List.of();

    return repositoryList
            .stream()
            .collect(Collectors.collectingAndThen(Collectors.toList(), list -> {
                if (list.isEmpty()) {
                    reference.set(HttpStatus.NOT_FOUND);
                    return Flowable.empty();
                }
                return Flowable.fromIterable(list);
            }));
}

public Maybe<ResponseEntity<Flowable<Person>>> controllerMethod() {
    var httpStatus = new AtomicReference<>(HttpStatus.OK);

    return Maybe.just(personList(httpStatus))
            .map(person -> ResponseEntity.status(httpStatus.get()))
            .body(person));
}