延迟队列是一种更为高效和可控的方式来处理定时任务,特别是在需要处理超时订单这类场景时。延迟队列可以让你将任务按照延迟时间有序地执行,而不需要通过轮询的方式频繁地检查订单表。
在Java中,可以使用Delayed
接口和DelayQueue
来实现延迟队列。以下是一个基于延迟队列的实时订单自动取消的示例:
import java.util.concurrent.Delayed;
import java.util.concurrent.TimeUnit;
public class DelayedOrderCancellation implements Delayed {
private final Order order;
private final long delayTime; // 延迟时间
public DelayedOrderCancellation(Order order, long delayTime) {
this.order = order;
this.delayTime = System.currentTimeMillis() + delayTime;
}
public Order getOrder() {
return order;
}
@Override
public long getDelay(TimeUnit unit) {
return unit.convert(delayTime - System.currentTimeMillis(), TimeUnit.MILLISECONDS);
}
@Override
public int compareTo(Delayed o) {
return Long.compare(this.delayTime, ((DelayedOrderCancellation) o).delayTime);
}
}
import java.util.concurrent.DelayQueue;
public class OrderCancellationManager {
private final DelayQueue<DelayedOrderCancellation> delayQueue = new DelayQueue<>();
public void scheduleOrderCancellation(Order order, long delayTime) {
DelayedOrderCancellation delayedOrderCancellation = new DelayedOrderCancellation(order, delayTime);
delayQueue.put(delayedOrderCancellation);
}
public void startOrderCancellationScheduler() {
new Thread(() -> {
while (true) {
try {
DelayedOrderCancellation delayedOrderCancellation = delayQueue.take();
processOrderCancellation(delayedOrderCancellation.getOrder());
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
}
}).start();
}
private void processOrderCancellation(Order order) {
// 处理订单取消逻辑
// ...
}
}
public class Main {
public static void main(String[] args) {
OrderCancellationManager orderCancellationManager = new OrderCancellationManager();
orderCancellationManager.startOrderCancellationScheduler();
// 在创建订单时调用
Order order = createOrder();
orderCancellationManager.scheduleOrderCancellation(order, TimeUnit.MINUTES.toMillis(30));
}
private static Order createOrder() {
// 创建订单的逻辑
// ...
}
}
在这个示例中,DelayedOrderCancellation
实现了Delayed
接口,它会根据订单的延迟时间在延迟队列中排序。OrderCancellationManager
负责将订单加入延迟队列,并通过单独的线程处理延迟队列中到期的任务,执行订单取消逻辑。
使用延迟队列的好处在于避免了频繁的轮询,使得系统更加高效。同时,通过设置合适的延迟时间,可以更灵活地控制任务的执行时间。