Java 当返回Mono<；Something>；时，不会调用Mono<；void>；.flatMap

我是WebFlux的新手.开发文件上传API.我想将上传的文件和元数据保存到数据库中，并将保存的实体作为响应返回.在filePart.transferTo的flatMap中未调用lambda表达式.我觉得使用block()会让使用WebFlux变得毫无意义.如有任何建议，我们不胜感激.

public Mono<Music> uploadMusic(FilePart filePart) throws IOException {
    File file = File.createTempFile("tmp-", filePart.filename());
    file.deleteOnExit();
    Music music = new Music();
    return filePart.transferTo(file).flatMap((it) -> {
        music.setFilePath(file.getAbsolutePath());
        music.setMeta(new Metadata());
        log.info(String.valueOf(music));
        return this.musicRepository.save(music);
    });
}

当我做代码片段测试时，我发现Mono<Void>0.flatMap返回Mono<SomeObj>似乎是个问题.

// Lambda expression not invoked
public Mono<Music> voidToObj(FilePart filePart) throws IOException {
    Music music = new Music();
    return Mono.just(music).then().flatMap(it -> {
        music.setMeta(new Metadata());
        log.info(music.toString());
        return Mono.just(music);
    });
}

// Lambda expression invoked
public Mono<Music> objToObj(FilePart filePart) throws IOException {
    Music music = new Music();
    return Mono.just(music).flatMap(it -> {
        music.setMeta(new Metadata());
        log.info(music.toString());
        return Mono.just(music);
    });
}