| egorianCalendar ）负责对此进行处理，所以不需要这样做。
清单 4. DailyIterator 类
package org.tiling.scheduling.examples.iterators;
import org.tiling.scheduling.ScheduleIterator;
import java.util.Calendar;
import java.util.Date;
/**
* A DailyIterator class returns a sequence of dates on subsequent days
* representing the same time each day.
*/
public class DailyIterator implements ScheduleIterator {
private final int hourOfDay, minute, second;
private final Calendar calendar = Calendar.getInstance();
public DailyIterator(int hourOfDay, int minute, int second) {
this(hourOfDay, minute, second, new Date());
}
public DailyIterator(int hourOfDay, int minute, int second, Date date) {
this.hourOfDay = hourOfDay;
this.minute = minute;
this.second = second;
calendar.setTime(date);
calendar.set(Calendar.HOUR_OF_DAY, hourOfDay);
calendar.set(Calendar.MINUTE, minute);
calendar.set(Calendar.SECOND, second);
calendar.set(Calendar.MILLISECOND, 0);
if (!calendar.getTime().before(date)) {
calendar.add(Calendar.DATE, -1);
}
}
public Date next() {
calendar.add(Calendar.DATE, 1);
return calendar.getTime();
}
}
在 Java 应用程序中计划重复执行的任务(4)
时间:2011-04-19 IBM Tom White
实现计划框架
在上一节，我们学习了如何使用计划框架，并将它与 Java 定时器框架进行了比较。下面 ，我将向您展示如何实现这个框架。除了 清单 3 中展示的 ScheduleIterator 接口，构成 这个框架的还有另外两个类 ―― Scheduler 和 SchedulerTask 。这些类实际上在内部使用 Timer 和 SchedulerTask，因为计划其实就是一系列的单次定时器。清单 5 和 6 显示了这 两个类的源代码：
清单 5. Scheduler
package org.tiling.scheduling;
import java.util.Date;
import java.util.Timer;
import java.util.TimerTask;
public class Scheduler {
class SchedulerTimerTask extends TimerTask {
private SchedulerTask schedulerTask;
private ScheduleIterator iterator;
public SchedulerTimerTask(SchedulerTask schedulerTask,
ScheduleIterator iterator) {
this.schedulerTask = schedulerTask;
this.iterator = iterator;
}
public void run() {
schedulerTask.run();
reschedule(schedulerTask, iterator);
}
}
private final Timer timer = new Timer();
public Scheduler() {
}
public void cancel() {
timer.cancel();
}
public void schedule(SchedulerTask schedulerTask,
ScheduleIterator iterator) {
Date time = iterator.next();
if (time == null) {
schedulerTask.cancel();
} else {
synchronized(schedulerTask.lock) {
if (schedulerTask.state != SchedulerTask.VIRGIN) {
throw new IllegalStateException("Task already
scheduled " + "or cancelled");
}
schedulerTas
|
