1、背景

项目中经常会用到类似一些需要延迟执行的功能，比如缓存。java提供了DelayQueue来很轻松的实现这种功能。Delayed接口中的getDelay方法返回值小于等于0的时候，表示时间到达，可以从DelayQueue中通过take()方法取的到期的对象。到期对象是实现了Delayed的类。

2、demo

2.1 依赖配置

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <!--非必须-->
        <dependency>
            <groupId>cn.hutool</groupId>
            <artifactId>hutool-all</artifactId>
            <version>5.8.0.M1</version>
        </dependency>
        <!--非必须-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.22</version>
        </dependency>
 
        <!--非必须-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

2.2 整体架构

** 工具类:**
执行任务所需的基础参数

 
import lombok.Data;
 
@Data
public class TaskBase {
    //任务参数，根据业务需求多少都行
    private String identifier;
 
    public TaskBase(String identifier) {
        this.identifier = identifier;
    }
}

执行的任务和时间

import cn.hutool.core.date.DateUtil;
 
import java.util.Date;
import java.util.concurrent.Delayed;
import java.util.concurrent.TimeUnit;
/**
 * 延时任务
 */
public class DelayTask implements Delayed {
    //任务参数
    final private TaskBase data;
    //任务的延时时间，单位毫秒
    final private long expire;
 
    /**
     * 构造延时任务
     *
     * @param data   业务数据
     * @param expire 任务延时时间（ms）
     */
    public DelayTask(TaskBase data, long expire) {
        super();
        this.data = data;
        this.expire = expire + System.currentTimeMillis();
    }
 
    public TaskBase getData() {
        return data;
    }
 
    public long getExpire() {
        return expire;
    }
 
    @Override
    public boolean equals(Object obj) {
        if (obj instanceof DelayTask) {
            return this.data.getIdentifier().equals(((DelayTask) obj).getData().getIdentifier());
        }
        return false;
    }
 
    @Override
    public String toString() {
        return "{" + "data:" + data.toString() + "," + "延时时间:" +expire+ DateUtil.format(new Date(),"yyyy.MM.dd HH:mm:ss") + "}";
    }
 
    @Override
    public long getDelay(TimeUnit unit) {
        return unit.convert(this.expire - System.currentTimeMillis(), unit);
    }
 
    @Override
    public int compareTo(Delayed o) {
        long delta = getDelay(TimeUnit.NANOSECONDS) - o.getDelay(TimeUnit.NANOSECONDS);
        return (int) delta;
    }
}

** 任务管理器：**

import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.CommandLineRunner;
import org.springframework.stereotype.Component;
import java.util.concurrent.DelayQueue;
import java.util.concurrent.Executors;
 
@Component
@Slf4j
public class DelayQueueManager implements CommandLineRunner {
 
    private final DelayQueue<DelayTask> delayQueue = new DelayQueue<>();
    private final Map<String, DelayTask> elements = new HashMap<>();
 
 
    /**
     * 加入到延时队列中
     *
     * @param task
     */
    public void put(DelayTask task) {
        log.error("加入延时任务：{}", task);
        delayQueue.put(task);
    }
 /**
     * 查询延时任务
     * @param taskID
     * @return
     */
    public DelayTask query(String taskID) {
        return elements.get(taskID);
    }
    /**
     * 取消延时任务
     *
     * @param task
     * @return
     */
    public boolean remove(DelayTask task) {
        log.error("取消延时任务：{}", task);
        return delayQueue.remove(task);
    }
 
    /**
     * 取消延时任务
     *
     * @param taskid
     * @return
     */
    public boolean remove(String taskid) {
        return remove(new DelayTask(new TaskBase(taskid), 0));
    }
 
    @Override
    public void run(String... args) throws Exception {
        log.info("初始化延时队列");
        Executors.newSingleThreadExecutor().execute(new Thread(this::excuteThread));
    }
 
    /**
     * 延时任务执行线程
     */
    private void excuteThread() {
        while (true) {
            try {
                DelayTask task = delayQueue.take();
                //执行任务
                processTask(task);
            } catch (InterruptedException e) {
                break;
            }
        }
    }
 
    /**
     * 内部执行延时任务
     *
     * @param task
     */
    private void processTask(DelayTask task) {
        //获取任务参数，执行业务task.getData().getIdentifier()
        log.error("执行延时任务：{}-{}", task, task.getData().getIdentifier());
    }
}

2.3 进行测试

import com.example.demo.task.DelayQueueManager;
import com.example.demo.task.DelayTask;
import com.example.demo.task.TaskBase;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
 
@SpringBootTest
class DemoApplicationTests {
    @Autowired
    private DelayQueueManager delayQueueManager;
 
    @Test
    void contextLoads() throws InterruptedException {
        //新增任务
        delayQueueManager.put(new DelayTask(new TaskBase("abc"), 1000 * 1));
        //新增任务
        delayQueueManager.put(new DelayTask(new TaskBase("abc"), 1000 * 5));
        //新增任务
        delayQueueManager.put(new DelayTask(new TaskBase("abc"), 1000 * 6));
        //测试任务需要下边代码执行，线上不用
        Thread.sleep(10 * 1000);
    }
 
}

参考链接: springboot延时任务