领域驱动设计（DDD）四 订单管理系统实践步骤

以下是基于 领域驱动设计（DDD） 的订单管理系统实践步骤，系统功能主要包括订单的创建、更新、查询和状态管理，采用 Spring Boot 框架进行实现。

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1. 需求分析

订单管理系统的基本功能：

1. 订单创建：用户下单创建订单。
2. 订单状态更新：更新订单状态（如已支付、已发货、已完成）。
3. 订单查询：支持按订单 ID 或用户查询订单信息。
4. 库存管理（简化版）：订单创建时检查并扣减库存。

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2. 领域划分与限界上下文

限界上下文

1. 订单上下文（Order Context）：负责订单的生命周期管理。
2. 库存上下文（Inventory Context）：负责商品库存的管理。

模块划分

src/main/java/com/example/order
├── application         # 应用层：处理用例逻辑
│   ├── service         # 应用服务
│   └── dto             # 数据传输对象
├── domain              # 领域层：业务逻辑
│   ├── model           # 领域模型（实体、值对象、聚合）
│   ├── repository      # 仓储接口
│   ├── service         # 领域服务
│   └── event           # 领域事件
├── infrastructure      # 基础设施层：技术实现
│   ├── repository      # 仓储实现
│   └── event           # 事件机制
└── interfaces          # 接口层：用户交互├── controller      # REST 接口└── vo              # 视图对象

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3. 代码实现

3.1 领域层设计

领域模型

(1) 订单实体

public class Order {private Long id;                  // 订单IDprivate String customerId;        // 用户IDprivate List<OrderItem> items;    // 订单项private OrderStatus status;       // 订单状态// 创建订单public Order(String customerId, List<OrderItem> items) {this.customerId = customerId;this.items = items;this.status = OrderStatus.CREATED;}// 更新订单状态public void updateStatus(OrderStatus status) {if (this.status.canTransitionTo(status)) {this.status = status;} else {throw new IllegalStateException("非法状态转换");}}// 计算总金额public BigDecimal calculateTotal() {return items.stream().map(item -> item.getPrice().multiply(BigDecimal.valueOf(item.getQuantity()))).reduce(BigDecimal.ZERO, BigDecimal::add);}// Getters and Setters
}

(2) 订单项值对象

public class OrderItem {private Long productId;   // 商品IDprivate int quantity;     // 数量private BigDecimal price; // 单价// 构造方法public OrderItem(Long productId, int quantity, BigDecimal price) {this.productId = productId;this.quantity = quantity;this.price = price;}// Getters and Setters
}

(3) 订单状态值对象

public enum OrderStatus {CREATED, PAID, SHIPPED, COMPLETED;// 状态转换规则public boolean canTransitionTo(OrderStatus newStatus) {return switch (this) {case CREATED -> newStatus == PAID;case PAID -> newStatus == SHIPPED;case SHIPPED -> newStatus == COMPLETED;default -> false;};}
}

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3.2 应用层设计

订单服务

@Service
public class OrderApplicationService {private final OrderRepository orderRepository;private final InventoryService inventoryService;public OrderApplicationService(OrderRepository orderRepository, InventoryService inventoryService) {this.orderRepository = orderRepository;this.inventoryService = inventoryService;}// 创建订单public Long createOrder(String customerId, List<OrderItemDto> itemDtos) {// 转换 DTO 为领域模型List<OrderItem> items = itemDtos.stream().map(dto -> new OrderItem(dto.getProductId(), dto.getQuantity(), dto.getPrice())).toList();// 检查库存items.forEach(item -> inventoryService.reserveStock(item.getProductId(), item.getQuantity()));// 创建订单Order order = new Order(customerId, items);orderRepository.save(order);return order.getId();}// 更新订单状态public void updateOrderStatus(Long orderId, OrderStatus status) {Order order = orderRepository.findById(orderId).orElseThrow(() -> new RuntimeException("订单不存在"));order.updateStatus(status);orderRepository.save(order);}// 查询订单public OrderDto getOrderById(Long orderId) {Order order = orderRepository.findById(orderId).orElseThrow(() -> new RuntimeException("订单不存在"));return OrderDto.fromDomain(order);}
}

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3.3 基础设施层设计

仓储实现

@Repository
public class JpaOrderRepository implements OrderRepository {private final SpringDataOrderJpaRepository jpaRepository;public JpaOrderRepository(SpringDataOrderJpaRepository jpaRepository) {this.jpaRepository = jpaRepository;}@Overridepublic void save(Order order) {jpaRepository.save(order);}@Overridepublic Optional<Order> findById(Long id) {return jpaRepository.findById(id);}
}

事件机制

@Component
public class DomainEventPublisher {private final ApplicationEventPublisher eventPublisher;public DomainEventPublisher(ApplicationEventPublisher eventPublisher) {this.eventPublisher = eventPublisher;}public void publish(Object event) {eventPublisher.publishEvent(event);}
}

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3.4 接口层设计

订单控制器

@RestController
@RequestMapping("/api/orders")
public class OrderController {private final OrderApplicationService orderService;public OrderController(OrderApplicationService orderService) {this.orderService = orderService;}@PostMappingpublic ResponseEntity<Long> createOrder(@RequestBody OrderRequest request) {Long orderId = orderService.createOrder(request.getCustomerId(), request.getItems());return ResponseEntity.status(HttpStatus.CREATED).body(orderId);}@PutMapping("/{orderId}/status")public ResponseEntity<Void> updateStatus(@PathVariable Long orderId, @RequestParam OrderStatus status) {orderService.updateOrderStatus(orderId, status);return ResponseEntity.ok().build();}@GetMapping("/{orderId}")public ResponseEntity<OrderDto> getOrderById(@PathVariable Long orderId) {return ResponseEntity.ok(orderService.getOrderById(orderId));}
}

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3.5 示例数据传输对象（DTO）

public class OrderDto {private Long id;private String customerId;private List<OrderItemDto> items;private OrderStatus status;public static OrderDto fromDomain(Order order) {return new OrderDto(order.getId(), order.getCustomerId(),order.getItems().stream().map(OrderItemDto::fromDomain).toList(),order.getStatus());}
}

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4. 运行与测试

数据库表结构（MySQL 示例）

CREATE TABLE orders (id BIGINT AUTO_INCREMENT PRIMARY KEY,customer_id VARCHAR(255),status VARCHAR(50)
);CREATE TABLE order_items (id BIGINT AUTO_INCREMENT PRIMARY KEY,order_id BIGINT,product_id BIGINT,quantity INT,price DECIMAL(10,2),FOREIGN KEY (order_id) REFERENCES orders(id)
);

测试示例

1. 创建订单

   POST /api/orders
   {"customerId": "123","items": [{ "productId": 1, "quantity": 2, "price": 50.00 },{ "productId": 2, "quantity": 1, "price": 100.00 }]
   }
   

2. 更新订单状态

   PUT /api/orders/1/status?status=PAID
   

3. 查询订单

   GET /api/orders/1
   

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这套设计是 DDD 的小型实践示例，后续可以扩展领域事件、复杂聚合和限界上下文的实现。