AKI*_*WEB 65 java background-thread timertask scheduledexecutorservice
我每天凌晨5点都在尝试完成某项任务.所以我决定使用ScheduledExecutorService这个,但到目前为止,我已经看到了一些示例,显示了如何每隔几分钟运行一次任务.
而且我无法找到任何显示如何在早上的特定时间(早上5点)每天运行任务的例子,同时也考虑夏令时的事实 -
以下是我的代码,每15分钟运行一次 -
public class ScheduledTaskExample {
private final ScheduledExecutorService scheduler = Executors
.newScheduledThreadPool(1);
public void startScheduleTask() {
/**
* not using the taskHandle returned here, but it can be used to cancel
* the task, or check if it's done (for recurring tasks, that's not
* going to be very useful)
*/
final ScheduledFuture<?> taskHandle = scheduler.scheduleAtFixedRate(
new Runnable() {
public void run() {
try {
getDataFromDatabase();
}catch(Exception ex) {
ex.printStackTrace(); //or loggger would be better
}
}
}, 0, 15, TimeUnit.MINUTES);
}
private void getDataFromDatabase() {
System.out.println("getting data...");
}
public static void main(String[] args) {
ScheduledTaskExample ste = new ScheduledTaskExample();
ste.startScheduleTask();
}
}
有没有办法,我可以安排一项任务,每天早上5点运行,同时ScheduledExecutorService考虑夏令时的事实？
也TimerTask就是这个或更好ScheduledExecutorService？
Sag*_*age 84
与目前的Java SE 8版本一样,它具有出色的日期时间API,java.time这种计算可以更轻松地完成,而不是使用 java.util.Calendar和java.util.Date.
现在作为使用您的用例计划任务的示例示例:
ZonedDateTime now = ZonedDateTime.now(ZoneId.of("America/Los_Angeles"));
ZonedDateTime nextRun = now.withHour(5).withMinute(0).withSecond(0);
if(now.compareTo(nextRun) > 0)
nextRun = nextRun.plusDays(1);
Duration duration = Duration.between(now, nextRun);
long initalDelay = duration.getSeconds();
ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
scheduler.scheduleAtFixedRate(new MyRunnableTask(),
initalDelay,
TimeUnit.DAYS.toSeconds(1),
TimeUnit.SECONDS);
该initalDelay计算问调度延迟在执行TimeUnit.SECONDS.对于此用例,单位毫秒及以下的时差问题似乎可以忽略不计.但是你仍然可以在几毫秒内使用duration.toMillis()和TimeUnit.MILLISECONDS处理调度计算.
而TimerTask对于这个还是ScheduledExecutorService更好？
不: ScheduledExecutorService看似好过TimerTask.StackOverflow已经为您解答了.
来自@PaddyD,
如果您希望在当地正确的时间运行,您仍然需要每年重启两次.scheduleAtFixedRate不会削减它,除非你对全年相同的UTC时间感到满意.
事实并且@PaddyD已经给出了一个解决方法(给他+1),我提供了一个带有Java8日期时间API的工作示例ScheduledExecutorService.使用守护程序线程很危险
class MyTaskExecutor
{
ScheduledExecutorService executorService = Executors.newScheduledThreadPool(1);
MyTask myTask;
volatile boolean isStopIssued;
public MyTaskExecutor(MyTask myTask$)
{
myTask = myTask$;
}
public void startExecutionAt(int targetHour, int targetMin, int targetSec)
{
Runnable taskWrapper = new Runnable(){
@Override
public void run()
{
myTask.execute();
startExecutionAt(targetHour, targetMin, targetSec);
}
};
long delay = computeNextDelay(targetHour, targetMin, targetSec);
executorService.schedule(taskWrapper, delay, TimeUnit.SECONDS);
}
private long computeNextDelay(int targetHour, int targetMin, int targetSec)
{
LocalDateTime localNow = LocalDateTime.now();
ZoneId currentZone = ZoneId.systemDefault();
ZonedDateTime zonedNow = ZonedDateTime.of(localNow, currentZone);
ZonedDateTime zonedNextTarget = zonedNow.withHour(targetHour).withMinute(targetMin).withSecond(targetSec);
if(zonedNow.compareTo(zonedNextTarget) > 0)
zonedNextTarget = zonedNextTarget.plusDays(1);
Duration duration = Duration.between(zonedNow, zonedNextTarget);
return duration.getSeconds();
}
public void stop()
{
executorService.shutdown();
try {
executorService.awaitTermination(1, TimeUnit.DAYS);
} catch (InterruptedException ex) {
Logger.getLogger(MyTaskExecutor.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
注意:
MyTask是一个功能的接口execute.ScheduledExecutorService,总是awaitTermination在调用shutdown它之后使用:总是有可能你的任务卡住/死锁,用户会永远等待.我之前用Calender给出的例子只是我提到的一个想法,我避免了精确的时间计算和夏令时问题.根据@PaddyD的抱怨更新了解决方案
Vic*_*tor 20
在Java 8中:
scheduler = Executors.newScheduledThreadPool(1);
//Change here for the hour you want ----------------------------------.at()
Long midnight=LocalDateTime.now().until(LocalDate.now().plusDays(1).atStartOfDay(), ChronoUnit.MINUTES);
scheduler.scheduleAtFixedRate(this, midnight, 1440, TimeUnit.MINUTES);
如果您没有能够使用Java 8的奢侈品,以下将满足您的需求:
public class DailyRunnerDaemon
{
private final Runnable dailyTask;
private final int hour;
private final int minute;
private final int second;
private final String runThreadName;
public DailyRunnerDaemon(Calendar timeOfDay, Runnable dailyTask, String runThreadName)
{
this.dailyTask = dailyTask;
this.hour = timeOfDay.get(Calendar.HOUR_OF_DAY);
this.minute = timeOfDay.get(Calendar.MINUTE);
this.second = timeOfDay.get(Calendar.SECOND);
this.runThreadName = runThreadName;
}
public void start()
{
startTimer();
}
private void startTimer();
{
new Timer(runThreadName, true).schedule(new TimerTask()
{
@Override
public void run()
{
dailyTask.run();
startTimer();
}
}, getNextRunTime());
}
private Date getNextRunTime()
{
Calendar startTime = Calendar.getInstance();
Calendar now = Calendar.getInstance();
startTime.set(Calendar.HOUR_OF_DAY, hour);
startTime.set(Calendar.MINUTE, minute);
startTime.set(Calendar.SECOND, second);
startTime.set(Calendar.MILLISECOND, 0);
if(startTime.before(now) || startTime.equals(now))
{
startTime.add(Calendar.DATE, 1);
}
return startTime.getTime();
}
}
它不需要任何外部库,并将占用夏令时.只需传递您想要将任务作为Calendar对象运行的时间,并将任务作为一个Runnable.例如:
Calendar timeOfDay = Calendar.getInstance();
timeOfDay.set(Calendar.HOUR_OF_DAY, 5);
timeOfDay.set(Calendar.MINUTE, 0);
timeOfDay.set(Calendar.SECOND, 0);
new DailyRunnerDaemon(timeOfDay, new Runnable()
{
@Override
public void run()
{
try
{
// call whatever your daily task is here
doHousekeeping();
}
catch(Exception e)
{
logger.error("An error occurred performing daily housekeeping", e);
}
}
}, "daily-housekeeping");
注意,计时器任务在守护程序线程中运行,不建议执行任何IO.如果需要使用User线程,则需要添加另一个取消计时器的方法.
如果必须使用a ScheduledExecutorService,只需将startTimer方法更改为以下内容:
private void startTimer()
{
Executors.newSingleThreadExecutor().schedule(new Runnable()
{
Thread.currentThread().setName(runThreadName);
dailyTask.run();
startTimer();
}, getNextRunTime().getTime() - System.currentTimeMillis(),
TimeUnit.MILLISECONDS);
}
我不确定该行为,但您可能需要一个停止方法,shutdownNow如果您沿着ScheduledExecutorService路线走,则会调用,否则当您尝试停止时,您的应用程序可能会挂起.
您是否考虑过使用Quartz Scheduler之类的东西？这个库有一个机制,用于使用类似cron的表达式来调度每天在设定的时间段运行的任务(看看CronScheduleBuilder).
一些示例代码(未测试):
public class GetDatabaseJob implements InterruptableJob
{
public void execute(JobExecutionContext arg0) throws JobExecutionException
{
getFromDatabase();
}
}
public class Example
{
public static void main(String[] args)
{
JobDetails job = JobBuilder.newJob(GetDatabaseJob.class);
// Schedule to run at 5 AM every day
ScheduleBuilder scheduleBuilder =
CronScheduleBuilder.cronSchedule("0 0 5 * * ?");
Trigger trigger = TriggerBuilder.newTrigger().
withSchedule(scheduleBuilder).build();
Scheduler scheduler = StdSchedulerFactory.getDefaultScheduler();
scheduler.scheduleJob(job, trigger);
scheduler.start();
}
}
预先有一些工作,你可能需要重写你的工作执行代码,但它应该可以让你更好地控制你的工作运行方式.如果需要,也可以更容易地更改计划.
Java8:
我的升级版本从顶部答案:
/**
* Execute {@link AppWork} once per day.
* <p>
* Created by aalexeenka on 29.12.2016.
*/
public class OncePerDayAppWorkExecutor {
private static final Logger LOG = AppLoggerFactory.getScheduleLog(OncePerDayAppWorkExecutor.class);
private ScheduledExecutorService executorService = Executors.newScheduledThreadPool(1);
private final String name;
private final AppWork appWork;
private final int targetHour;
private final int targetMin;
private final int targetSec;
private volatile boolean isBusy = false;
private volatile ScheduledFuture<?> scheduledTask = null;
private AtomicInteger completedTasks = new AtomicInteger(0);
public OncePerDayAppWorkExecutor(
String name,
AppWork appWork,
int targetHour,
int targetMin,
int targetSec
) {
this.name = "Executor [" + name + "]";
this.appWork = appWork;
this.targetHour = targetHour;
this.targetMin = targetMin;
this.targetSec = targetSec;
}
public void start() {
scheduleNextTask(doTaskWork());
}
private Runnable doTaskWork() {
return () -> {
LOG.info(name + " [" + completedTasks.get() + "] start: " + minskDateTime());
try {
isBusy = true;
appWork.doWork();
LOG.info(name + " finish work in " + minskDateTime());
} catch (Exception ex) {
LOG.error(name + " throw exception in " + minskDateTime(), ex);
} finally {
isBusy = false;
}
scheduleNextTask(doTaskWork());
LOG.info(name + " [" + completedTasks.get() + "] finish: " + minskDateTime());
LOG.info(name + " completed tasks: " + completedTasks.incrementAndGet());
};
}
private void scheduleNextTask(Runnable task) {
LOG.info(name + " make schedule in " + minskDateTime());
long delay = computeNextDelay(targetHour, targetMin, targetSec);
LOG.info(name + " has delay in " + delay);
scheduledTask = executorService.schedule(task, delay, TimeUnit.SECONDS);
}
private static long computeNextDelay(int targetHour, int targetMin, int targetSec) {
ZonedDateTime zonedNow = minskDateTime();
ZonedDateTime zonedNextTarget = zonedNow.withHour(targetHour).withMinute(targetMin).withSecond(targetSec).withNano(0);
if (zonedNow.compareTo(zonedNextTarget) > 0) {
zonedNextTarget = zonedNextTarget.plusDays(1);
}
Duration duration = Duration.between(zonedNow, zonedNextTarget);
return duration.getSeconds();
}
public static ZonedDateTime minskDateTime() {
return ZonedDateTime.now(ZoneId.of("Europe/Minsk"));
}
public void stop() {
LOG.info(name + " is stopping.");
if (scheduledTask != null) {
scheduledTask.cancel(false);
}
executorService.shutdown();
LOG.info(name + " stopped.");
try {
LOG.info(name + " awaitTermination, start: isBusy [ " + isBusy + "]");
// wait one minute to termination if busy
if (isBusy) {
executorService.awaitTermination(1, TimeUnit.MINUTES);
}
} catch (InterruptedException ex) {
LOG.error(name + " awaitTermination exception", ex);
} finally {
LOG.info(name + " awaitTermination, finish");
}
}
}