📚 Series: Java Backend Zero to Hello 📂 Phân đoạn: Phase 8: Project thực tế 📖 Nội dung: BÀI 8.4: CART & ORDER MODULE 💡 Khóa học lập trình Backend Java & Spring Boot chuẩn doanh nghiệp từ con số 0.

BÀI 8.4: CART & ORDER MODULE

Mục tiêu

• Implement Cart management
• Implement Order creation
• Quản lý trạng thái đơn hàng
• Tích hợp payment

1. CART MODULE

1.1 Entities

@Entity
@Table(name = "carts")
@Getter @Setter
@NoArgsConstructor @AllArgsConstructor @Builder
public class Cart {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @OneToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "user_id", nullable = false, unique = true)
    private User user;

    @OneToMany(mappedBy = "cart", cascade = CascadeType.ALL, orphanRemoval = true)
    private List<CartItem> items = new ArrayList<>();

    @CreatedDate
    @Column(name = "created_at", updatable = false)
    private LocalDateTime createdAt;

    @LastModifiedDate
    @Column(name = "updated_at")
    private LocalDateTime updatedAt;

    public void addItem(CartItem item) {
        items.add(item);
        item.setCart(this);
    }

    public void removeItem(CartItem item) {
        items.remove(item);
        item.setCart(null);
    }

    public BigDecimal getTotalAmount() {
        return items.stream()
            .map(item -> item.getProduct().getPrice()
                .multiply(BigDecimal.valueOf(item.getQuantity())))
            .reduce(BigDecimal.ZERO, BigDecimal::add);
    }
}

@Entity
@Table(name = "cart_items")
@Getter @Setter
@NoArgsConstructor @AllArgsConstructor @Builder
public class CartItem {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "cart_id", nullable = false)
    private Cart cart;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "product_id", nullable = false)
    private Product product;

    @Column(nullable = false)
    private Integer quantity;

    public BigDecimal getSubtotal() {
        return product.getPrice().multiply(BigDecimal.valueOf(quantity));
    }
}

1.2 Service

@Service
@RequiredArgsConstructor
@Slf4j
public class CartService {

    private final CartRepository cartRepository;
    private final ProductRepository productRepository;
    private final UserRepository userRepository;

    @Transactional
    public CartResponse getCart(Long userId) {
        Cart cart = getOrCreateCart(userId);
        return CartResponse.from(cart);
    }

    @Transactional
    public CartResponse addItem(Long userId, AddCartItemRequest request) {
        Cart cart = getOrCreateCart(userId);
        Product product = productRepository.findById(request.productId())
            .orElseThrow(() -> new NotFoundException("Product not found"));

        if (product.getStock() < request.quantity()) {
            throw new BusinessException("INSUFFICIENT_STOCK",
                "Not enough stock");
        }

        Optional<CartItem> existingItem = cart.getItems().stream()
            .filter(item -> item.getProduct().getId().equals(product.getId()))
            .findFirst();

        if (existingItem.isPresent()) {
            CartItem item = existingItem.get();
            item.setQuantity(item.getQuantity() + request.quantity());
        } else {
            CartItem item = CartItem.builder()
                .product(product)
                .quantity(request.quantity())
                .build();
            cart.addItem(item);
        }

        Cart saved = cartRepository.save(cart);
        return CartResponse.from(saved);
    }

    @Transactional
    public CartResponse updateItemQuantity(Long userId, Long productId, Integer quantity) {
        Cart cart = getOrCreateCart(userId);

        CartItem item = cart.getItems().stream()
            .filter(i -> i.getProduct().getId().equals(productId))
            .findFirst()
            .orElseThrow(() -> new NotFoundException("Item not in cart"));

        if (quantity <= 0) {
            cart.removeItem(item);
        } else {
            if (item.getProduct().getStock() < quantity) {
                throw new BusinessException("INSUFFICIENT_STOCK", "Not enough stock");
            }
            item.setQuantity(quantity);
        }

        return CartResponse.from(cartRepository.save(cart));
    }

    @Transactional
    public CartResponse removeItem(Long userId, Long productId) {
        Cart cart = getOrCreateCart(userId);

        CartItem item = cart.getItems().stream()
            .filter(i -> i.getProduct().getId().equals(productId))
            .findFirst()
            .orElseThrow(() -> new NotFoundException("Item not in cart"));

        cart.removeItem(item);
        return CartResponse.from(cartRepository.save(cart));
    }

    @Transactional
    public void clearCart(Long userId) {
        Cart cart = getOrCreateCart(userId);
        cart.getItems().clear();
        cartRepository.save(cart);
    }

    private Cart getOrCreateCart(Long userId) {
        return cartRepository.findByUserId(userId)
            .orElseGet(() -> {
                User user = userRepository.findById(userId)
                    .orElseThrow(() -> new NotFoundException("User not found"));
                Cart newCart = Cart.builder().user(user).build();
                return cartRepository.save(newCart);
            });
    }
}

2. ORDER MODULE

2.1 Entities

@Entity
@Table(name = "orders")
@EntityListeners(AuditingEntityListener.class)
@Getter @Setter
@NoArgsConstructor @AllArgsConstructor @Builder
public class Order {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(name = "order_number", unique = true, nullable = false, length = 50)
    private String orderNumber;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "user_id", nullable = false)
    private User user;

    @Enumerated(EnumType.STRING)
    @Column(nullable = false, length = 20)
    private OrderStatus status = OrderStatus.PENDING;

    @Column(name = "total_amount", nullable = false, precision = 12, scale = 2)
    private BigDecimal totalAmount;

    @Column(name = "shipping_fee", precision = 12, scale = 2)
    private BigDecimal shippingFee = BigDecimal.ZERO;

    @Column(precision = 12, scale = 2)
    private BigDecimal discount = BigDecimal.ZERO;

    @Column(name = "final_amount", nullable = false, precision = 12, scale = 2)
    private BigDecimal finalAmount;

    @Column(name = "shipping_address", columnDefinition = "TEXT")
    private String shippingAddress;

    @Column(name = "shipping_phone", length = 20)
    private String shippingPhone;

    @Column(name = "shipping_name", length = 100)
    private String shippingName;

    @Column(columnDefinition = "TEXT")
    private String note;

    @Enumerated(EnumType.STRING)
    @Column(name = "payment_method", length = 20)
    private PaymentMethod paymentMethod;

    @Enumerated(EnumType.STRING)
    @Column(name = "payment_status", length = 20)
    private PaymentStatus paymentStatus = PaymentStatus.PENDING;

    @OneToMany(mappedBy = "order", cascade = CascadeType.ALL, orphanRemoval = true)
    private List<OrderItem> items = new ArrayList<>();

    @CreatedDate
    @Column(name = "created_at", updatable = false)
    private LocalDateTime createdAt;

    @LastModifiedDate
    @Column(name = "updated_at")
    private LocalDateTime updatedAt;
}

public enum OrderStatus {
    PENDING, CONFIRMED, PROCESSING, SHIPPED, DELIVERED, CANCELLED
}

public enum PaymentMethod {
    COD, BANK_TRANSFER, MOMO, VNPAY
}

public enum PaymentStatus {
    PENDING, PAID, FAILED, REFUNDED
}

2.2 OrderItem Entity

@Entity
@Table(name = "order_items")
@Getter @Setter
@NoArgsConstructor @AllArgsConstructor @Builder
public class OrderItem {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "order_id", nullable = false)
    private Order order;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "product_id", nullable = false)
    private Product product;

    @Column(name = "product_name", nullable = false)
    private String productName;

    @Column(name = "product_price", nullable = false, precision = 12, scale = 2)
    private BigDecimal productPrice;

    @Column(nullable = false)
    private Integer quantity;

    @Column(nullable = false, precision = 12, scale = 2)
    private BigDecimal subtotal;
}

2.3 Service

@Service
@RequiredArgsConstructor
@Slf4j
public class OrderService {

    private final OrderRepository orderRepository;
    private final CartRepository cartRepository;
    private final ProductRepository productRepository;
    private final UserRepository userRepository;

    @Transactional
    public OrderResponse createOrder(Long userId, CreateOrderRequest request) {
        User user = userRepository.findById(userId)
            .orElseThrow(() -> new NotFoundException("User not found"));

        Cart cart = cartRepository.findByUserId(userId)
            .orElseThrow(() -> new BusinessException("CART_EMPTY", "Cart is empty"));

        if (cart.getItems().isEmpty()) {
            throw new BusinessException("CART_EMPTY", "Cart is empty");
        }

        // Validate stock
        for (CartItem item : cart.getItems()) {
            Product product = item.getProduct();
            if (product.getStock() < item.getQuantity()) {
                throw new BusinessException("INSUFFICIENT_STOCK",
                    "Not enough stock for: " + product.getName());
            }
        }

        // Create order
        Order order = Order.builder()
            .orderNumber(generateOrderNumber())
            .user(user)
            .status(OrderStatus.PENDING)
            .shippingAddress(request.shippingAddress())
            .shippingPhone(request.shippingPhone())
            .shippingName(request.shippingName())
            .note(request.note())
            .paymentMethod(request.paymentMethod())
            .paymentStatus(PaymentStatus.PENDING)
            .shippingFee(BigDecimal.valueOf(30000))
            .build();

        BigDecimal totalAmount = BigDecimal.ZERO;

        for (CartItem cartItem : cart.getItems()) {
            Product product = cartItem.getProduct();
            BigDecimal subtotal = product.getPrice()
                .multiply(BigDecimal.valueOf(cartItem.getQuantity()));

            OrderItem orderItem = OrderItem.builder()
                .product(product)
                .productName(product.getName())
                .productPrice(product.getPrice())
                .quantity(cartItem.getQuantity())
                .subtotal(subtotal)
                .build();

            order.addItem(orderItem);
            totalAmount = totalAmount.add(subtotal);

            // Update stock
            product.setStock(product.getStock() - cartItem.getQuantity());
            productRepository.save(product);
        }

        order.setTotalAmount(totalAmount);
        order.setFinalAmount(totalAmount.add(order.getShippingFee()).subtract(order.getDiscount()));

        Order saved = orderRepository.save(order);

        // Clear cart
        cart.getItems().clear();
        cartRepository.save(cart);

        log.info("Order created: {}", saved.getOrderNumber());
        return OrderResponse.from(saved);
    }

    public Page<OrderResponse> getUserOrders(Long userId, Pageable pageable) {
        return orderRepository.findByUserId(userId, pageable)
            .map(OrderResponse::from);
    }

    public OrderResponse getOrderById(Long userId, Long orderId) {
        Order order = orderRepository.findById(orderId)
            .orElseThrow(() -> new NotFoundException("Order not found"));

        if (!order.getUser().getId().equals(userId)) {
            throw new BusinessException("FORBIDDEN", "Not your order");
        }

        return OrderResponse.from(order);
    }

    @Transactional
    public OrderResponse cancelOrder(Long userId, Long orderId) {
        Order order = orderRepository.findById(orderId)
            .orElseThrow(() -> new NotFoundException("Order not found"));

        if (!order.getUser().getId().equals(userId)) {
            throw new BusinessException("FORBIDDEN", "Not your order");
        }

        if (order.getStatus() != OrderStatus.PENDING) {
            throw new BusinessException("CANNOT_CANCEL",
                "Cannot cancel order in status: " + order.getStatus());
        }

        order.setStatus(OrderStatus.CANCELLED);

        // Restore stock
        for (OrderItem item : order.getItems()) {
            Product product = item.getProduct();
            product.setStock(product.getStock() + item.getQuantity());
            productRepository.save(product);
        }

        return OrderResponse.from(orderRepository.save(order));
    }

    @Transactional
    public OrderResponse updateStatus(Long orderId, OrderStatus status) {
        Order order = orderRepository.findById(orderId)
            .orElseThrow(() -> new NotFoundException("Order not found"));

        order.setStatus(status);
        return OrderResponse.from(orderRepository.save(order));
    }

    private String generateOrderNumber() {
        return "ORD-" + LocalDateTime.now().format(DateTimeFormatter.ofPattern("yyyyMMddHHmmss"))
            + "-" + UUID.randomUUID().toString().substring(0, 4).toUpperCase();
    }
}

2.4 Controller

@RestController
@RequestMapping("/orders")
@RequiredArgsConstructor
@Tag(name = "Order", description = "Order APIs")
public class OrderController {

    private final OrderService orderService;

    @PostMapping
    @Operation(summary = "Create order")
    public ResponseEntity<ApiResponse<OrderResponse>> createOrder(
            @AuthenticationPrincipal User user,
            @RequestBody @Valid CreateOrderRequest request) {
        return ResponseEntity.status(HttpStatus.CREATED)
            .body(ApiResponse.success("Order created",
                orderService.createOrder(user.getId(), request)));
    }

    @GetMapping("/me")
    @Operation(summary = "Get my orders")
    public ApiResponse<PageResponse<OrderResponse>> getMyOrders(
            @AuthenticationPrincipal User user,
            @RequestParam(defaultValue = "0") int page,
            @RequestParam(defaultValue = "10") int size) {
        Pageable pageable = PageRequest.of(page, size,
            Sort.by(Sort.Direction.DESC, "createdAt"));
        return ApiResponse.success(PageResponse.from(
            orderService.getUserOrders(user.getId(), pageable)));
    }

    @GetMapping("/me/{id}")
    @Operation(summary = "Get my order by ID")
    public ApiResponse<OrderResponse> getMyOrder(
            @AuthenticationPrincipal User user,
            @PathVariable Long id) {
        return ApiResponse.success(orderService.getOrderById(user.getId(), id));
    }

    @PatchMapping("/me/{id}/cancel")
    @Operation(summary = "Cancel my order")
    public ApiResponse<OrderResponse> cancelMyOrder(
            @AuthenticationPrincipal User user,
            @PathVariable Long id) {
        return ApiResponse.success(orderService.cancelOrder(user.getId(), id));
    }

    @GetMapping
    @PreAuthorize("hasRole('ADMIN')")
    @Operation(summary = "Get all orders (Admin)")
    public ApiResponse<PageResponse<OrderResponse>> getAllOrders(
            @RequestParam(defaultValue = "0") int page,
            @RequestParam(defaultValue = "10") int size) {
        Pageable pageable = PageRequest.of(page, size);
        return ApiResponse.success(PageResponse.from(
            orderService.getAllOrders(pageable)));
    }

    @PatchMapping("/{id}/status")
    @PreAuthorize("hasRole('ADMIN')")
    @Operation(summary = "Update order status (Admin)")
    public ApiResponse<OrderResponse> updateStatus(
            @PathVariable Long id,
            @RequestParam OrderStatus status) {
        return ApiResponse.success(orderService.updateStatus(id, status));
    }
}

3. PAYMENT MODULE

3.1 Service

@Service
@RequiredArgsConstructor
@Slf4j
public class PaymentService {

    private final PaymentRepository paymentRepository;
    private final OrderRepository orderRepository;

    @Transactional
    public PaymentResponse processPayment(Long orderId, PaymentMethod method) {
        Order order = orderRepository.findById(orderId)
            .orElseThrow(() -> new NotFoundException("Order not found"));

        if (order.getPaymentStatus() == PaymentStatus.PAID) {
            throw new BusinessException("ALREADY_PAID", "Order already paid");
        }

        // Mock payment processing
        Payment payment = Payment.builder()
            .order(order)
            .amount(order.getFinalAmount())
            .method(method)
            .status(PaymentStatus.PAID)
            .transactionId(UUID.randomUUID().toString())
            .paidAt(LocalDateTime.now())
            .build();

        Payment saved = paymentRepository.save(payment);

        order.setPaymentStatus(PaymentStatus.PAID);
        order.setStatus(OrderStatus.CONFIRMED);
        orderRepository.save(order);

        log.info("Payment processed for order: {}", order.getOrderNumber());
        return PaymentResponse.from(saved);
    }
}

4. TESTING

@SpringBootTest
@Testcontainers
@AutoConfigureMockMvc
class OrderIntegrationTest {

    @Container
    @ServiceConnection
    static PostgreSQLContainer<?> postgres = new PostgreSQLContainer<>("postgres:16");

    @Autowired private MockMvc mockMvc;
    @Autowired private ObjectMapper objectMapper;
    @Autowired private UserRepository userRepository;
    @Autowired private ProductRepository productRepository;
    @Autowired private CartRepository cartRepository;

    @Test
    void shouldCreateOrder() throws Exception {
        // Setup
        User user = createUser();
        Product product = createProduct();
        addToCart(user, product, 2);

        // Create order
        CreateOrderRequest request = new CreateOrderRequest(
            "123 Street", "0123456789", "An", null, PaymentMethod.COD
        );

        mockMvc.perform(post("/orders")
                .header("Authorization", "Bearer " + getToken(user))
                .contentType(MediaType.APPLICATION_JSON)
                .content(objectMapper.writeValueAsString(request)))
            .andExpect(status().isCreated())
            .andExpect(jsonPath("$.data.orderNumber").exists())
            .andExpect(jsonPath("$.data.status").value("PENDING"));
    }
}

5. BÀI TẬP

Bài 1: Cart

Implement Cart với add, update, remove items.

Bài 2: Order

Implement Order creation từ Cart.

Bài 3: Payment

Implement payment processing (mock).

Bài 4: Test

Viết integration test cho order flow.

Bài tiếp theo: 8.5 Statistics & Deployment

🧭 Điều hướng bài học

• ⬅️ Bài trước: BÀI 8.3: PRODUCT & CATEGORY MODULE
• ➡️ Bài tiếp theo: BÀI 8.5: STATISTICS & DEPLOYMENT
• 📑 Toàn bộ lộ trình: Java Backend Zero to Hello

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