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一文掌握Spring事件驱动模型实战

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一文掌握Spring事件驱动模型实战

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今天跟大家介绍一个简单的购物车提交订单的示例代码 ， 如何使用Spring的事件驱动模型来模拟下单流程中扣减商品库存、扣减会员积分抵钱、核销会员优惠券等场景：
JAVACopy code// 自定义事件类public class OrderSubmittedEvent extends ApplicationEvent {private List<OrderItem> orderItems;private Member member;private Coupon coupon;public OrderSubmittedEvent(Object source, List<OrderItem> orderItems, Member member, Coupon coupon) {super(source);this.orderItems = orderItems;this.member = member;this.coupon = coupon;}public List<OrderItem> getOrderItems() {return orderItems;}public Member getMember() {return member;}public Coupon getCoupon() {return coupon;}}// 事件监听器：扣减商品库存@Componentpublic class StockEventHandler implements ApplicationListener<OrderSubmittedEvent> {@Autowiredprivate StockService stockService;@Overridepublic void onApplicationEvent(OrderSubmittedEvent event) {List<OrderItem> orderItems = event.getOrderItems();for (OrderItem orderItem : orderItems) {stockService.decreaseStock(orderItem.getProductId(), orderItem.getQuantity());}}}// 事件监听器：扣减会员积分抵钱@Componentpublic class PointEventHandler implements ApplicationListener<OrderSubmittedEvent> {@Autowiredprivate PointService pointService;@Overridepublic void onApplicationEvent(OrderSubmittedEvent event) {Member member = event.getMember();int totalPoints = 0;List<OrderItem> orderItems = event.getOrderItems();for (OrderItem orderItem : orderItems) {totalPoints += orderItem.getPoints();}pointService.decreasePoints(member.getId(), totalPoints);}}// 事件监听器：核销会员优惠券@Componentpublic class CouponEventHandler implements ApplicationListener<OrderSubmittedEvent> {@Autowiredprivate CouponService couponService;@Overridepublic void onApplicationEvent(OrderSubmittedEvent event) {Coupon coupon = event.getCoupon();if (coupon != null) {couponService.useCoupon(coupon.getId());}}}// 订单服务类@Servicepublic class OrderService {@Autowiredprivate ApplicationContext applicationContext;public void submitOrder(List<OrderItem> orderItems, Member member, Coupon coupon) {// 创建订单Order order = createOrder(orderItems, member, coupon);// 发布订单提交事件OrderSubmittedEvent orderSubmittedEvent = new OrderSubmittedEvent(this, orderItems, member, coupon);applicationContext.publishEvent(orderSubmittedEvent);}private Order createOrder(List<OrderItem> orderItems, Member member, Coupon coupon) {// 创建订单逻辑}}// 商品库存服务类@Servicepublic class StockService {public void decreaseStock(Long productId, int quantity) {// 扣减商品库存逻辑}}// 会员积分服务类@Servicepublic class PointService {public void decreasePoints(Long memberId, int points) {// 扣减会员积分逻辑}}// 会员优惠券服务类@Servicepublic class CouponService {public void useCoupon(Long couponId) {// 核销会员优惠券逻辑}}在示例代码中 ， OrderSubmittedEvent类表示订单提交事件 ， StockEventHandler类表示扣减商品库存的事件监听器 ， PointEventHandler类表示扣减会员积分抵钱的事件监听器 ， CouponEventHandler类表示核销会员优惠券的事件监听器 ， OrderService类表示订单服务类 ， StockService类表示商品库存服务类 ， PointService类表示会员积分服务类 ， CouponService类表示会员优惠券服务类 。
当调用OrderService类的submitOrder()方法时 ， 会创建订单并发布订单提交事件 ， StockEventHandler类、PointEventHandler类和CouponEventHandler类中的onApplicationEvent()方法将被自动调用 ， 从而实现扣减商品库存、扣减会员积分抵钱、核销会员优惠券的操作 。
在实际项目中 ， 上述示例代码仅仅是一个简单的示例 ， 实际业务逻辑可能更加复杂 ， 需要根据具体情况进行调整和优化 。同时 ， 为了保证事件处理的正确性和稳定性 ， 需要对事件处理方法进行严格的测试和调试 。
为了保证事件处理的顺序和可靠性 ， 可以使用Spring框架提供的@Order注解来指定事件监听器的执行顺序 。可以在StockEventHandler类上添加@Order注解 ， 指定其执行顺序为1 ， 而在PointEventHandler类上添加@Order注解 ， 指定其执行顺序为2 ， 这样就可以保证扣减商品库存的操作先于扣减会员积分抵钱的操作 。
【一文掌握Spring事件驱动模型实战】javaCopy code// 事件监听器：扣减商品库存@Component@Order(1)public class StockEventHandler implements ApplicationListener<OrderSubmittedEvent> {// ...}// 事件监听器：扣减会员积分抵钱@Component@Order(2)public class PointEventHandler implements ApplicationListener<OrderSubmittedEvent> {// ...}


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