// 1. 從確定值創(chuàng)建
Mono<String> mono1 = Mono.just("Hello, World!");
// 2. 創(chuàng)建空 Mono
Mono<String> mono2 = Mono.empty();
// 3. 從可能為null的值創(chuàng)建（如果value為null，則返回空Mono）
Mono<String> mono3 = Mono.justOrNull(someNullableValue);
// 4. 從可調(diào)用對象創(chuàng)建（延遲計(jì)算）
Mono<String> mono4 = Mono.fromCallable(() -> {
    // 可能拋出異常的計(jì)算
    return expensiveComputation();
});
// 5. 從 Future 創(chuàng)建
CompletableFuture<String> future = CompletableFuture.supplyAsync(() -> "Result");
Mono<String> mono5 = Mono.fromFuture(future);
// 6. 從 Supplier 創(chuàng)建
Mono<String> mono6 = Mono.fromSupplier(() -> generateValue());
// 7. 創(chuàng)建錯誤 Mono
Mono<String> mono7 = Mono.error(new RuntimeException("Something went wrong"));
// 8. 延遲創(chuàng)建（直到有訂閱者時才執(zhí)行）
Mono<String> mono8 = Mono.defer(() -> {
    return Mono.just(System.currentTimeMillis() + " - generated");
});

Mono<User> userMono = getUserById(userId)
    .filter(user -> user.isActive())  // 過濾非活躍用戶
    .map(user -> {                    // 轉(zhuǎn)換數(shù)據(jù)
        UserDTO dto = new UserDTO();
        dto.setName(user.getName());
        dto.setEmail(user.getEmail());
        return dto;
    })
    .flatMap(dto -> {                 // 異步轉(zhuǎn)換到另一個Mono
        return sendNotification(dto.getEmail())
            .map(success -> dto);
    })
    .doOnNext(dto -> {                // 副作用操作
        log.info("Processed user: {}", dto.getName());
    })
    .doOnError(error -> {             // 錯誤時的副作用
        log.error("Failed to process user", error);
    })
    .timeout(Duration.ofSeconds(5))   // 設(shè)置超時
    .retry(3);                        // 失敗時重試3次

Mono<String> safeMono = riskyOperation()
    .onErrorResume(error -> {          // 發(fā)生錯誤時提供備用Mono
        log.warn("Operation failed, using fallback", error);
        return Mono.just("Fallback Value");
    })
    .onErrorReturn("Default Value")    // 發(fā)生錯誤時返回默認(rèn)值
    .onErrorMap(error -> {             // 轉(zhuǎn)換錯誤類型
        return new BusinessException("Operation failed", error);
    })
    .doFinally(signal -> {             // 最終清理（無論成功或失?。?
        cleanupResources();
    });

// 1. 最簡單的訂閱（觸發(fā)執(zhí)行但忽略結(jié)果）
mono.subscribe();
// 2. 帶成功回調(diào)的訂閱
mono.subscribe(
    value -> System.out.println("Received: " + value)
);
// 3. 帶成功和錯誤回調(diào)的訂閱
mono.subscribe(
    value -> System.out.println("Received: " + value),
    error -> System.err.println("Error: " + error.getMessage())
);
// 4. 完整的訂閱（成功、錯誤、完成）
mono.subscribe(
    value -> System.out.println("Received: " + value),
    error -> System.err.println("Error: " + error.getMessage()),
    () -> System.out.println("Completed successfully")
);
// 5. 帶訂閱回調(diào)的訂閱
mono.subscribe(
    new Subscriber<String>() {
        @Override
        public void onSubscribe(Subscription s) {
            s.request(1);  // 請求數(shù)據(jù)
        }
        @Override
        public void onNext(String value) {
            System.out.println("Received: " + value);
        }
        @Override
        public void onError(Throwable t) {
            System.err.println("Error: " + t.getMessage());
        }
        @Override
        public void onComplete() {
            System.out.println("Completed");
        }
    }
);

Mono<String> debugMono = someOperation()
    .log("my.mono")  // 添加日志
    .checkpoint("debug point")  // 添加檢查點(diǎn)
    .doOnSubscribe(s -> log.debug("Subscribed"))
    .doOnNext(v -> log.debug("Next: {}", v))
    .doOnError(e -> log.error("Error: {}", e.getMessage()))
    .doOnCancel(() -> log.debug("Cancelled"))
    .doOnSuccess(v -> log.debug("Completed with: {}", v));