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备案查询站长之家,福州专业网站制作的公司,网站后台网址忘记了 php,上海文明城市建设网站目录核心实现： 这种实现方式的优势： 在实际项目中，你可能需要： 事件驱动往往是在一个微服务内部实现的领域时间是DDD架构中比较常见的概念在领域层内部的一个模型更改了状态或者发生了一些行为向外发送一些通知这些通…

核心实现：

这种实现方式的优势：

在实际项目中，你可能需要：

事件驱动往往是在一个微服务内部实现的

领域时间是DDD架构中比较常见的概念

在领域层内部的一个模型更改了状态或者发生了一些行为

向外发送一些通知

这些通知叫做领域时间

类似于MQ

这个通知不会在分布式系统内部传递

只会在单个微服务内部传递

和MQ一样这样能解耦

我们可以通过发布事件的方式进行一种松耦合的通信

以下是DDD架构中领域层事件驱动的Java实现示例，展示如何通过领域事件实现松耦合的业务逻辑：

import java.time.LocalDateTime;
import java.util.ArrayList;
import java.util.List;
import java.util.UUID;
import java.util.concurrent.CompletableFuture;
import java.util.function.Consumer;/*** 领域事件接口* 所有领域事件需实现此接口*/
interface DomainEvent {UUID getEventId();LocalDateTime getOccurredOn();
}/*** 领域事件抽象基类* 提供事件ID和发生时间的基础实现*/
abstract class BaseDomainEvent implements DomainEvent {private final UUID eventId;private final LocalDateTime occurredOn;protected BaseDomainEvent() {this.eventId = UUID.randomUUID();this.occurredOn = LocalDateTime.now();}@Overridepublic UUID getEventId() {return eventId;}@Overridepublic LocalDateTime getOccurredOn() {return occurredOn;}
}/*** 订单已创建事件*/
class OrderCreatedEvent extends BaseDomainEvent {private final String orderId;private final String customerId;public OrderCreatedEvent(String orderId, String customerId) {this.orderId = orderId;this.customerId = customerId;}public String getOrderId() {return orderId;}public String getCustomerId() {return customerId;}
}/*** 订单已支付事件*/
class OrderPaidEvent extends BaseDomainEvent {private final String orderId;private final LocalDateTime paymentTime;public OrderPaidEvent(String orderId, LocalDateTime paymentTime) {this.orderId = orderId;this.paymentTime = paymentTime;}public String getOrderId() {return orderId;}public LocalDateTime getPaymentTime() {return paymentTime;}
}/*** 库存扣减事件*/
class InventoryDeductedEvent extends BaseDomainEvent {private final String productId;private final int quantity;public InventoryDeductedEvent(String productId, int quantity) {this.productId = productId;this.quantity = quantity;}public String getProductId() {return productId;}public int getQuantity() {return quantity;}
}/*** 领域事件发布者接口*/
interface DomainEventPublisher {void publish(DomainEvent event);
}/*** 领域事件订阅者接口*/
interface DomainEventSubscriber<T extends DomainEvent> {void handleEvent(T event);Class<T> subscribedToEventType();
}/*** 领域事件总线（单例实现）* 负责事件的注册、发布和分发*/
class DomainEventBus implements DomainEventPublisher {private static final DomainEventBus INSTANCE = new DomainEventBus();private final List<DomainEventSubscriber<?>> subscribers = new ArrayList<>();private DomainEventBus() {}public static DomainEventBus getInstance() {return INSTANCE;}public <T extends DomainEvent> void register(DomainEventSubscriber<T> subscriber) {subscribers.add(subscriber);}@Overridepublic void publish(DomainEvent event) {subscribers.stream().filter(subscriber -> subscriber.subscribedToEventType().isInstance(event)).forEach(subscriber -> dispatch(event, subscriber));}@SuppressWarnings("unchecked")private <T extends DomainEvent> void dispatch(DomainEvent event, DomainEventSubscriber<?> subscriber) {// 同步处理事件((DomainEventSubscriber<T>) subscriber).handleEvent((T) event);// 异步处理示例：// CompletableFuture.runAsync(() -> //     ((DomainEventSubscriber<T>) subscriber).handleEvent((T) event)// );}
}/*** 领域事件聚合根接口* 定义聚合根应具备的事件管理能力*/
interface EventSourcedAggregateRoot {List<DomainEvent> getDomainEvents();void clearDomainEvents();
}/*** 订单实体（聚合根）* 集成领域事件功能*/
class Order implements EventSourcedAggregateRoot {private final String id;private final String customerId;private OrderStatus status;private final List<DomainEvent> domainEvents = new ArrayList<>();public Order(String id, String customerId) {this.id = id;this.customerId = customerId;this.status = OrderStatus.CREATED;// 创建订单时发布订单创建事件registerEvent(new OrderCreatedEvent(id, customerId));}public void pay() {if (status != OrderStatus.CREATED) {throw new IllegalStateException("订单状态错误，当前状态：" + status);}this.status = OrderStatus.PAID;// 支付时发布订单已支付事件registerEvent(new OrderPaidEvent(id, LocalDateTime.now()));}private void registerEvent(DomainEvent event) {domainEvents.add(event);}@Overridepublic List<DomainEvent> getDomainEvents() {return new ArrayList<>(domainEvents);}@Overridepublic void clearDomainEvents() {domainEvents.clear();}// Getterspublic String getId() {return id;}public String getCustomerId() {return customerId;}public OrderStatus getStatus() {return status;}
}/*** 库存服务（领域服务）* 处理库存相关业务逻辑*/
class InventoryService implements DomainEventSubscriber<OrderPaidEvent> {private final InventoryRepository inventoryRepository;public InventoryService(InventoryRepository inventoryRepository) {this.inventoryRepository = inventoryRepository;}@Overridepublic void handleEvent(OrderPaidEvent event) {// 订单支付后扣减库存// 实际应用中需要根据订单ID查询订单详情获取商品信息// 这里简化处理System.out.println("处理订单支付事件：订单ID=" + event.getOrderId());// 扣减库存逻辑// inventoryRepository.deductStock(productId, quantity);// 发布库存扣减事件DomainEventBus.getInstance().publish(new InventoryDeductedEvent("P001", 1));}@Overridepublic Class<OrderPaidEvent> subscribedToEventType() {return OrderPaidEvent.class;}
}/*** 库存仓储接口*/
interface InventoryRepository {void deductStock(String productId, int quantity);
}/*** 库存仓储实现（示例）*/
class InMemoryInventoryRepository implements InventoryRepository {@Overridepublic void deductStock(String productId, int quantity) {System.out.println("扣减库存：商品ID=" + productId + "，数量=" + quantity);// 实际实现会更新数据库中的库存记录}
}/*** 订单服务（应用服务）* 协调领域对象和事件处理*/
class OrderApplicationService {private final OrderRepository orderRepository;private final DomainEventPublisher eventPublisher;public OrderApplicationService(OrderRepository orderRepository, DomainEventPublisher eventPublisher) {this.orderRepository = orderRepository;this.eventPublisher = eventPublisher;}public void createOrder(String customerId, List<OrderItem> items) {// 创建订单String orderId = UUID.randomUUID().toString();Order order = new Order(orderId, customerId);// 持久化订单orderRepository.save(order);// 发布领域事件publishEvents(order);}public void payOrder(String orderId) {// 获取订单Order order = orderRepository.findById(orderId).orElseThrow(() -> new IllegalArgumentException("订单不存在"));// 执行支付业务逻辑order.pay();// 持久化更新orderRepository.save(order);// 发布领域事件publishEvents(order);}private void publishEvents(Order order) {order.getDomainEvents().forEach(eventPublisher::publish);order.clearDomainEvents();}
}/*** 订单仓储接口*/
interface OrderRepository {void save(Order order);java.util.Optional<Order> findById(String orderId);
}/*** 主程序演示*/
public class Main {public static void main(String[] args) {// 初始化组件InventoryRepository inventoryRepository = new InMemoryInventoryRepository();InventoryService inventoryService = new InventoryService(inventoryRepository);OrderRepository orderRepository = new InMemoryOrderRepository();DomainEventPublisher eventPublisher = DomainEventBus.getInstance();// 注册事件订阅者DomainEventBus.getInstance().register(inventoryService);// 初始化订单应用服务OrderApplicationService orderService = new OrderApplicationService(orderRepository, eventPublisher);// 创建订单orderService.createOrder("C001", Collections.emptyList());// 支付订单（触发事件）orderService.payOrder("ORD12345");}
}

这个示例展示了DDD领域层事件驱动的