异步处理：不懂，留个记录以后看

    @Bean
    @Autowired
    public RouterFunction personFindAll(UserRepository userRepository){
        return RouterFunctions.route(RequestPredicates.GET("person/find/all"),
                serverRequest -> {
                    Collection users = userRepository.findAll();
                    Flux userFlux = Flux.fromIterable(users);
                    return ServerResponse.ok().body(userFlux);
                });
    }