Java任务调度
1.Timer
package com.qhong; import java.text.SimpleDateFormat; import java.util.Date; import java.util.Timer; import java.util.TimerTask; public class Main { public static void main(String[] args) { Timer timer = new Timer(); long delay1 = 1 * 1000; long period1 = 1000; // 从现在开始 1 秒钟之后,每隔 1 秒钟执行一次 job1 timer.schedule(new TimerTest("job1" +DateUtils.format(new Date(),"yyyy-MM-dd HH:mm:ss")), delay1, period1); long delay2 = 2 * 1000; long period2 = 2000; // 从现在开始 2 秒钟之后,每隔 2 秒钟执行一次 job2 timer.schedule(new TimerTest("job2"), delay2, period2); } } class TimerTest extends TimerTask { private String jobName = ""; public TimerTest(String jobName) { super(); this.jobName = jobName; } @Override public void run() { System.out.println("execute " + jobName); } } class DateUtils { /** 时间格式(yyyy-MM-dd) */ public final static String DATE_PATTERN = "yyyy-MM-dd"; /** 时间格式(yyyy-MM-dd HH:mm:ss) */ public final static String DATE_TIME_PATTERN = "yyyy-MM-dd HH:mm:ss"; public static String format(Date date) { return format(date, DATE_PATTERN); } public static String format(Date date, String pattern) { if(date != null){ SimpleDateFormat df = new SimpleDateFormat(pattern); return df.format(date); } return null; } }
execute job12017-03-10 19:48:45 execute job2 execute job12017-03-10 19:48:45 execute job12017-03-10 19:48:45 execute job2 execute job12017-03-10 19:48:45 execute job12017-03-10 19:48:45 execute job2 execute job12017-03-10 19:48:45 execute job12017-03-10 19:48:45 execute job2 execute job12017-03-10 19:48:45 execute job12017-03-10 19:48:45
Timer 的优点在于简单易用,但由于所有任务都是由同一个线程来调度,因此所有任务都是串行执行的,同一时间只能有一个任务在执行,前一个任务的延迟或异常都将会影响到之后的任务。
ScheduledExecutor
package com.qhong; import java.util.Date; import java.text.SimpleDateFormat; import java.util.concurrent.Executors; import java.util.concurrent.ScheduledExecutorService; import java.util.concurrent.TimeUnit; public class Main { public static void main(String[] args) { ScheduledExecutorService service = Executors.newScheduledThreadPool(10); long initialDelay1 = 1; long period1 = 1; // 从现在开始1秒钟之后,每隔1秒钟执行一次job1 service.scheduleAtFixedRate( new ScheduledExecutorTest("job1"), initialDelay1, period1, TimeUnit.SECONDS); long initialDelay2 = 2; long delay2 = 2; // 从现在开始2秒钟之后,每隔2秒钟执行一次job2 service.scheduleWithFixedDelay( new ScheduledExecutorTest("job2"), initialDelay2, delay2, TimeUnit.SECONDS); } } class ScheduledExecutorTest implements Runnable { private String jobName = ""; public ScheduledExecutorTest(String jobName) { super(); this.jobName = jobName; } @Override public void run() { System.out.println("execute "+ DateUtils.format(new Date(),"yyyy-MM-dd HH:mm:ss") + jobName); } } class DateUtils { /** 时间格式(yyyy-MM-dd) */ public final static String DATE_PATTERN = "yyyy-MM-dd"; /** 时间格式(yyyy-MM-dd HH:mm:ss) */ public final static String DATE_TIME_PATTERN = "yyyy-MM-dd HH:mm:ss"; public static String format(Date date) { return format(date, DATE_PATTERN); } public static String format(Date date, String pattern) { if(date != null){ SimpleDateFormat df = new SimpleDateFormat(pattern); return df.format(date); } return null; } }
execute 2017-03-10 20:03:53job1 execute 2017-03-10 20:03:54job2 execute 2017-03-10 20:03:54job1 execute 2017-03-10 20:03:55job1 execute 2017-03-10 20:03:56job1 execute 2017-03-10 20:03:56job2 execute 2017-03-10 20:03:57job1 execute 2017-03-10 20:03:58job1 execute 2017-03-10 20:03:58job2 execute 2017-03-10 20:03:59job1 execute 2017-03-10 20:04:00job1 execute 2017-03-10 20:04:00job2 execute 2017-03-10 20:04:01job1 execute 2017-03-10 20:04:02job1 execute 2017-03-10 20:04:02job2
展示了 ScheduledExecutorService 中两种最常用的调度方法 ScheduleAtFixedRate 和 ScheduleWithFixedDelay。
ScheduleAtFixedRate 每次执行时间为上一次任务开始起向后推一个时间间隔,即每次执行时间为 :initialDelay, initialDelay+period, initialDelay+2*period, …;
ScheduleWithFixedDelay 每次执行时间为上一次任务结束起向后推一个时间间隔,即每次执行时间为:initialDelay, initialDelay+executeTime+delay, initialDelay+2*executeTime+2*delay。
由此可见,ScheduleAtFixedRate 是基于固定时间间隔进行任务调度,ScheduleWithFixedDelay 取决于每次任务执行的时间长短,是基于不固定时间间隔进行任务调度。
用 ScheduledExecutor 和 Calendar 实现复杂任务调度
package com.qhong; import java.util.Calendar; import java.util.Date; import java.util.TimerTask; import java.util.concurrent.Executors; import java.util.concurrent.ScheduledExecutorService; import java.util.concurrent.TimeUnit; public class Main { public static void main(String[] args) { ScheduledExceutorTest2 test = new ScheduledExceutorTest2("job1"); //获取当前时间 Calendar currentDate = Calendar.getInstance(); long currentDateLong = currentDate.getTime().getTime(); System.out.println("Current Date = " + currentDate.getTime().toString()); //计算满足条件的最近一次执行时间 Calendar earliestDate = test .getEarliestDate(currentDate, 3, 16, 38, 10); long earliestDateLong = earliestDate.getTime().getTime(); System.out.println("Earliest Date = " + earliestDate.getTime().toString()); //计算从当前时间到最近一次执行时间的时间间隔 long delay = earliestDateLong - currentDateLong; //计算执行周期为一星期 long period = 7 * 24 * 60 * 60 * 1000; ScheduledExecutorService service = Executors.newScheduledThreadPool(10); //从现在开始delay毫秒之后,每隔一星期执行一次job1 service.scheduleAtFixedRate(test, delay, period, TimeUnit.MILLISECONDS); } } class ScheduledExceutorTest2 extends TimerTask { private String jobName = ""; public ScheduledExceutorTest2(String jobName) { super(); this.jobName = jobName; } @Override public void run() { System.out.println("Date = "+new Date()+", execute " + jobName); } /** * 计算从当前时间currentDate开始,满足条件dayOfWeek, hourOfDay, * minuteOfHour, secondOfMinite的最近时间 * @return */ public Calendar getEarliestDate(Calendar currentDate, int dayOfWeek, int hourOfDay, int minuteOfHour, int secondOfMinite) { //计算当前时间的WEEK_OF_YEAR,DAY_OF_WEEK, HOUR_OF_DAY, MINUTE,SECOND等各个字段值 int currentWeekOfYear = currentDate.get(Calendar.WEEK_OF_YEAR); int currentDayOfWeek = currentDate.get(Calendar.DAY_OF_WEEK); int currentHour = currentDate.get(Calendar.HOUR_OF_DAY); int currentMinute = currentDate.get(Calendar.MINUTE); int currentSecond = currentDate.get(Calendar.SECOND); //如果输入条件中的dayOfWeek小于当前日期的dayOfWeek,则WEEK_OF_YEAR需要推迟一周 boolean weekLater = false; if (dayOfWeek < currentDayOfWeek) { weekLater = true; } else if (dayOfWeek == currentDayOfWeek) { //当输入条件与当前日期的dayOfWeek相等时,如果输入条件中的 //hourOfDay小于当前日期的 //currentHour,则WEEK_OF_YEAR需要推迟一周 if (hourOfDay < currentHour) { weekLater = true; } else if (hourOfDay == currentHour) { //当输入条件与当前日期的dayOfWeek, hourOfDay相等时, //如果输入条件中的minuteOfHour小于当前日期的 //currentMinute,则WEEK_OF_YEAR需要推迟一周 if (minuteOfHour < currentMinute) { weekLater = true; } else if (minuteOfHour == currentSecond) { //当输入条件与当前日期的dayOfWeek, hourOfDay, //minuteOfHour相等时,如果输入条件中的 //secondOfMinite小于当前日期的currentSecond, //则WEEK_OF_YEAR需要推迟一周 if (secondOfMinite < currentSecond) { weekLater = true; } } } } if (weekLater) { //设置当前日期中的WEEK_OF_YEAR为当前周推迟一周 currentDate.set(Calendar.WEEK_OF_YEAR, currentWeekOfYear + 1); } // 设置当前日期中的DAY_OF_WEEK,HOUR_OF_DAY,MINUTE,SECOND为输入条件中的值。 currentDate.set(Calendar.DAY_OF_WEEK, dayOfWeek); currentDate.set(Calendar.HOUR_OF_DAY, hourOfDay); currentDate.set(Calendar.MINUTE, minuteOfHour); currentDate.set(Calendar.SECOND, secondOfMinite); return currentDate; } }
Current Date = Fri Mar 10 20:40:46 CST 2017
Earliest Date = Tue Mar 14 16:38:10 CST 2017
Quartz:
https://www.ibm.com/developerworks/cn/java/j-lo-taskschedule/