Java DelayQueue实现延时任务的示例详解

import org.jetbrains.annotations.NotNull;

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.concurrent.Delayed;
import java.util.concurrent.TimeUnit;

/**
 * 延时订单任务
 */
public class OrderDelayObject implements Delayed {
  private String name;
  private long delayTime;   //延时时间
  //实际业务中这里传订单信息对象，我这里只做demo，所以使用字符串了
  private String order;

  public OrderDelayObject(String name, long delayTime, String order) {
    this.name = name;
    //延时时间加上当前时间
    this.delayTime = System.currentTimeMillis() + delayTime;
    this.order = order;
  }

  //获取延时任务的倒计时时间
  @Override
  public long getDelay(TimeUnit unit) {
    long diff = delayTime - System.currentTimeMillis();
    return unit.convert(diff, TimeUnit.MILLISECONDS);
  }

  //延时任务队列，按照延时时间元素排序，实现Comparable接口
  @Override
  public int compareTo(@NotNull Delayed obj) {
    return Long.compare(this.delayTime, ((OrderDelayObject) obj).delayTime);
  }

  @Override
  public String toString() {
    Date date = new Date(delayTime);
    SimpleDateFormat sd = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

    return "\nOrderDelayObject:{"
            + "name=" + name
            + ", time=" + sd.format(date)
            + ", order=" + order
            + "}";
  }
} 

@Bean("orderDelayQueue")
public DelayQueue<OrderDelayObject> orderDelayQueue(){
    return new DelayQueue<OrderDelayObject>();
}

@Resource
private DelayQueue<OrderDelayObject> orderDelayQueue;

//发起订单下单的时候将订单演示对象放入orderDelayQueue
orderDelayQueue.add(
        new OrderDelayObject(
                "订单延时取消任务",
                30 * 60 * 1000,    //延时30分钟
                "延时任务订单对象信息"
        )
);

@Component
public class DelayObjectConsumer  implements InitializingBean {

  @Resource
  private DelayQueue<OrderDelayObject> orderDelayQueue;

  @Override
  public void afterPropertiesSet() throws Exception {
    while (true) {
      OrderDelayObject task = orderDelayQueue.take();
      System.out.println(task.toString());
      System.out.println(task.getOrder());
      //根据order订单信息，去查询该订单的支付信息
      //如果用户没有进行支付，将订单从数据库中关闭
      //如果订单并发量比较大，这里可以考虑异步或线程池的方式进行处理
    }
  }
}