簡介
非同步處理、任務調度和事件驅動架構是企業應用中廣泛使用的三種模式。 Spring Boot 4 支援虛擬執行緒 (Java 21+)，讓非同步處理比以往更有效率。
1. @Async — 非同步處理
1.1 啟用非同步
@Configuration
@EnableAsync
public class AsyncConfig { }
1.2 使用@Async
@Service
public class NotificationService {
// Fire-and-forget
@Async
public void sendWelcomeEmail(String email, String name) {
log.info("Sending email to {} on thread: {}",
email, Thread.currentThread().getName());
emailClient.send(email, "Welcome " + name, buildWelcomeBody(name));
}
// Trả về CompletableFuture
@Async
public CompletableFuture<ReportResult> generateReport(ReportRequest request) {
ReportResult result = reportGenerator.generate(request);
return CompletableFuture.completedFuture(result);
}
}
1.3 虛擬執行緒（Spring Boot 4 + Java 21+）
# application.yml
spring:
threads:
virtual:
enabled: true # Tự động dùng Virtual Threads cho @Async
// Custom executor với Virtual Threads
@Bean
public AsyncTaskExecutor applicationTaskExecutor() {
return new TaskExecutorAdapter(
Executors.newVirtualThreadPerTaskExecutor());
}
1.4 組合多個非同步操作
@Service
public class DashboardService {
public DashboardResponse getDashboard(Long userId) {
CompletableFuture<UserStats> statsFuture =
statsService.getUserStats(userId);
CompletableFuture<List<Notification>> notifFuture =
notificationService.getRecent(userId);
CompletableFuture<List<Order>> ordersFuture =
orderService.getRecentOrders(userId);
// Chờ tất cả hoàn thành
CompletableFuture.allOf(statsFuture, notifFuture, ordersFuture).join();
return new DashboardResponse(
statsFuture.join(),
notifFuture.join(),
ordersFuture.join()
);
}
}
1.5 非同步錯誤處理
@Component
public class AsyncExceptionHandler implements AsyncUncaughtExceptionHandler {
@Override
public void handleUncaughtException(Throwable ex, Method method,
Object... params) {
log.error("Async error in {}: {}", method.getName(), ex.getMessage(), ex);
}
}
@Configuration
@EnableAsync
public class AsyncConfig implements AsyncConfigurer {
@Override
public AsyncUncaughtExceptionHandler getAsyncUncaughtExceptionHandler() {
return new AsyncExceptionHandler();
}
}
2. @Scheduled — 任務調度
2.1 啟用調度
@Configuration
@EnableScheduling
public class SchedulingConfig { }
2.2 時間表類型
@Component
public class ScheduledTasks {
// Fixed rate: 5 giây một lần (tính từ lúc BẮT ĐẦU task trước)
@Scheduled(fixedRate = 5000)
public void checkHealth() {
log.info("Health check at {}", Instant.now());
}
// Fixed delay: 5 giây sau khi task trước HOÀN THÀNH
@Scheduled(fixedDelay = 5000, initialDelay = 10000)
public void syncData() {
log.info("Syncing data...");
}
// Cron expression: 2 giờ sáng mỗi ngày
@Scheduled(cron = "0 0 2 * * *")
public void dailyCleanup() {
log.info("Running daily cleanup...");
tempFileService.deleteExpired();
}
// Cấu hình từ properties
@Scheduled(cron = "${app.scheduler.report-cron:0 0 6 * * MON}")
public void weeklyReport() {
reportService.generateWeeklyReport();
}
}
2.3 Cron 表達式備忘單
┌───────────── second (0-59)
│ ┌───────────── minute (0-59)
│ │ ┌───────────── hour (0-23)
│ │ │ ┌───────────── day of month (1-31)
│ │ │ │ ┌───────────── month (1-12)
│ │ │ │ │ ┌───────────── day of week (0-7, 0=Sun)
│ │ │ │ │ │
* * * * * *
0 0 2 * * * → 2:00 AM mỗi ngày
0 */15 * * * * → Mỗi 15 phút
0 0 9-17 * * MON-FRI → Mỗi giờ 9h-17h, thứ 2-6
3. Spring 應用程式事件
3.1 建立自訂事件
// Event dùng record
public record OrderCreatedEvent(
Long orderId,
Long userId,
BigDecimal totalAmount,
Instant createdAt
) { }
3.2 發布事件
@Service
public class OrderService {
private final ApplicationEventPublisher eventPublisher;
public OrderService(ApplicationEventPublisher eventPublisher) {
this.eventPublisher = eventPublisher;
}
@Transactional
public OrderResponse createOrder(CreateOrderRequest request) {
Order order = orderRepository.save(mapToOrder(request));
// Publish event
eventPublisher.publishEvent(new OrderCreatedEvent(
order.getId(),
order.getUserId(),
order.getTotalAmount(),
Instant.now()
));
return OrderResponse.from(order);
}
}
3.3 訂閱事件
@Component
public class OrderEventListener {
// Đồng bộ (cùng thread, cùng transaction)
@EventListener
public void onOrderCreated(OrderCreatedEvent event) {
log.info("Order {} created, amount: {}",
event.orderId(), event.totalAmount());
}
// Async listener
@Async
@EventListener
public void sendOrderConfirmation(OrderCreatedEvent event) {
emailService.sendOrderConfirmation(event.userId(), event.orderId());
}
// Chỉ xử lý SAU khi transaction commit thành công
@TransactionalEventListener(phase = TransactionPhase.AFTER_COMMIT)
public void afterOrderCommitted(OrderCreatedEvent event) {
inventoryService.decreaseStock(event.orderId());
analyticsService.trackOrder(event);
}
// Conditional listener
@EventListener(condition = "#event.totalAmount() > 1000000")
public void onHighValueOrder(OrderCreatedEvent event) {
alertService.notifyManager(event);
}
}
3.4 應用程式中的事件流
OrderController
│
▼
OrderService.createOrder()
│── Save to DB
│── Publish OrderCreatedEvent
│
▼
┌─────────────────────────────────┐
│ Event Listeners │
│ ├── NotificationListener │ ← @Async: gửi email
│ ├── InventoryListener │ ← @TransactionalEventListener
│ ├── AnalyticsListener │ ← @Async: track metrics
│ └── AuditListener │ ← Ghi audit log
└─────────────────────────────────┘
總結
- @Async 與虛擬執行緒（Spring Boot 4）結合，實現高效並發處理，無需手動執行緒池管理
- @Scheduled 支援後台任務的固定速率、固定延遲、cron 表達式
- 應用程式事件（發布/訂閱）有助於解耦業務邏輯，@TransactionalEventListener 確保事件僅在事務提交後處理
練習
- 實現非同步電子郵件服務：建立使用者後，發送非同步歡迎電子郵件。使用 AsyncUncaughtExceptionHandler 處理錯誤 2.建立每天凌晨2點執行的排程任務，刪除過期的會話和暫存文件 3.實作事件驅動的訂單處理：OrderCreatedEvent→NotificationListener + InventoryListener + AnalyticsListener，使用@TransactionalEventListener