当http服务器响应404时未调用Spring WebClient异步回调

Mono<Account> accountMono = client.get()
    .uri("accounturl")
    .accept(MediaType.APPLICATION_JSON)
    .exchange()
    .flatMap(response -> {
                            if (response.statusCode().equals(HttpStatus.OK)) {
                              return response.bodyToMono(Account.class);
                            } else { 
                              return Mono.empty();
                            }
                          });

accountMono.subscribe(result -> callback(result));  

```

Server response 404 . 我试图创建一个空帐户,但是 callback() Mono 不发射。