java

public class Inventory {
    private String productId;
    private int quantity;
    public Inventory(String productId, int quantity) {
        this.productId = productId;
        this.quantity = quantity;
    }
    // getters and setters
}

java

// 觀察者接口
public interface InventoryObserver {
    void update(Inventory inventory);
}
// 具體的觀察者實現(xiàn)
public class InventoryUpdateNotifier {
    private List<InventoryObserver> observers = new ArrayList<>();
    public void addObserver(InventoryObserver observer) {
        synchronized (observers) {
            if (!observers.contains(observer)) {
                observers.add(observer);
            }
        }
    }
    public void removeObserver(InventoryObserver observer) {
        synchronized (observers) {
            observers.remove(observer);
        }
    }
    public void notifyObservers(Inventory inventory) {
        for (InventoryObserver observer : observers) {
            observer.update(inventory);
        }
    }
}

java

@Configuration
public class AppConfig {
    @Bean
    public InventoryUpdateNotifier inventoryUpdateNotifier() {
        return new InventoryUpdateNotifier();
    }
}

java

@RestController
@RequestMapping("/inventory")
public class InventoryController {
    @Autowired
    private InventoryUpdateNotifier notifier;
    @PostMapping("/update")
    public ResponseEntity<String> update(@RequestBody Inventory inventory) {
        // 更新庫存邏輯...
        notifier.notifyObservers(inventory);
        return ResponseEntity.ok("Inventory updated successfully");
    }
}

java

@Component
public class StockMonitor implements InventoryObserver {
    @Override
    public void update(Inventory inventory) {
        System.out.println("Stock Monitor: Inventory of product " + inventory.getProductId() + " has been updated to " + inventory.getQuantity());
    }
}

shell

curl -X POST http://localhost:8080/inventory/update -H 'Content-Type: application/json' -d '{"productId":"123", "quantity":5}'