Cron 表达式解析，crontab表达式解析

前言

将类似
30 8 * * 1,4,6
这种的表达式解析为执行时间，获取下一次或者多次的执行时间。

一、代码展示

代码如下（示例）：

import cn.hutool.core.date.DateUtil;import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.Set;
import java.util.TreeSet;import static java.util.Calendar.DATE;
import static java.util.Calendar.DAY_OF_YEAR;
/*** @author ******* Created on 2022/3/15.** Cron 表达式解析*/
public class CronParser {private String cronExp;public CronParser(String exp) {this.cronExp = exp;}public Date nextDate(Date start) {Calendar lastCal = Calendar.getInstance();lastCal.setTime(start);//上一次执行时间字段int lastYear = lastCal.get(Calendar.YEAR);int lastMonth = lastCal.get(Calendar.MONTH) + 1;int lastDay = lastCal.get(Calendar.DAY_OF_MONTH);int lastMonthDay = this.encodeMonthday(lastMonth, lastDay);int lastHour = lastCal.get(Calendar.HOUR_OF_DAY);int lastMinute = lastCal.get(Calendar.MINUTE);int lastSecond = lastCal.get(Calendar.SECOND);//下一次执行时间字段Integer newMonthDay = null;Integer newHour = null;Integer newMinute = null;Integer newYear = lastYear;//解析cron表达式String[] exps = cronExp.split("\\s+");CronRange minute = parseRange(exps[0], 0, 59);CronRange hour = parseRange(exps[1], 0, 23);CronRange day = parseRange(exps[2], 1, 31);CronRange month = parseRange(exps[3], 1, 12);CronRange week = parseRange(exps[4], 1, 7);CronRange monthDay = this.calMonthDay(month, day, week);if (monthDay.isEmpty()) {return null;}boolean isNotFound = false;if (monthDay.inRange(lastMonthDay)) {if (hour.inRange(lastHour)) {if (minute.inRange(lastMinute)) {newMinute = minute.getNextValue(lastMinute);}if (newMinute == null) {//如果分钟找不到，需要对小时进行递增newHour = hour.getNextValue(lastHour);isNotFound = newHour == null;newMinute = minute.getMin();} else {newHour = lastHour;}}if (newHour == null) {if (isNotFound) {//如果小时找不到，需要对天数进行递增if (monthDay.isAll()) {Calendar c = Calendar.getInstance();c.setTime(start);c.add(DATE, 1);newMonthDay = this.encodeMonthday(c.get(Calendar.MONTH) + 1, c.get(Calendar.DAY_OF_MONTH));} else {//如果跨年了就找不到newMonthDay = monthDay.getNextValue(lastMonthDay);}} else {newMonthDay = lastMonthDay;}newHour = hour.getMin();newMinute = minute.getMin();} else {newMonthDay = lastMonthDay;}} else {//天如果不在范围内，需要对天进行递增newMonthDay = monthDay.getNextValue(lastMonthDay);newHour = hour.getMin();newMinute = minute.getMin();}if (newMonthDay == null) {//跨年newYear = newYear + 1;if (monthDay.isAll()) {//1月1日newMonthDay = 0x0101;} else {newMonthDay = monthDay.getMin();}newHour = hour.getMin();newMinute = minute.getMin();}Calendar newCal = Calendar.getInstance();newCal.set(Calendar.MONTH, this.decodeMonth(newMonthDay) - 1);newCal.set(Calendar.DAY_OF_MONTH, decodeDay(newMonthDay));newCal.set(Calendar.HOUR_OF_DAY, newHour);newCal.set(Calendar.MINUTE, newMinute);newCal.set(Calendar.SECOND, lastSecond);newCal.set(Calendar.YEAR, newYear);return newCal.getTime();}/*** 将月和日合并成一个int型整数* @param month* @param day* @return*/public int encodeMonthday(int month, int day) {return (day & 0x000000FF) | (month << 8 & 0x0000FF00);}/*** 解码月* @param monthDay* @return*/public int decodeMonth(int monthDay) {return (monthDay & 0x0000FF00) >> 8;}/*** 解码日* @param monthDay* @return*/public int decodeDay(int monthDay) {return (monthDay & 0x000000FF);}private CronRange calMonthDay(CronRange month, CronRange day, CronRange week) {CronRange monthDay = new CronRange();if (month.isAll() && day.isAll() && week.isAll()) {//如果都是全范围的就不进行计算monthDay.setReturnAll(true);return monthDay;}int[] monthDays = {31, 0, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};//如果是闰年就是29天monthDays[1] = Calendar.getInstance().getActualMaximum(DAY_OF_YEAR) > 365 ? 29 : 28;Set<Integer> rangeMonth = month.getRange();for (Integer m : rangeMonth) {for (int d = 1; d <= monthDays[m - 1]; ++d) {if (day.inRange(d)) {//判断周的逻辑if (!week.isAll()) {Calendar cal = Calendar.getInstance();cal.set(Calendar.MONTH, m - 1);cal.set(Calendar.DAY_OF_MONTH, d);int w = cal.get(Calendar.DAY_OF_WEEK) - 1;//周日-周六==>1-7w = w == 0 ? 7 : w;if (!week.inRange(w)) {continue;}}monthDay.addRange(this.encodeMonthday(m, d));}}}return monthDay;}/*** 解析表达式的取值范围和循环周期** @param exp* @param start* @param end* @return*/public CronRange parseRange(String exp, int start, int end) {String[] exps = exp.trim().split("/");CronRange range = new CronRange();if (exps.length > 1) {range.setCycle(Integer.parseInt(exps[1]));}if (exps[0].trim().length() == 0) {range.range(start, end);} else if ("*".equals(exps[0])) {range.range(start, end);range.setReturnAll(exps.length == 1);} else if (exps[0].contains("-")) {String[] ss = exps[0].split("-");range.range(Integer.parseInt(ss[0]), Integer.parseInt(ss[1]));} else if (exps[0].contains(",")) {String[] ss = exps[0].split(",");for (String s : ss) {range.addRange(Integer.parseInt(s));}} else {range.addRange(Integer.parseInt(exps[0]));}return range;}public static void main(String[] args) throws ParseException {String cronExp = "30 8 * * 1,4,6";CronParser parser = new CronParser(cronExp);String lastExecuteDateStr = "2022-03-12 22:23:22";Date date = DateUtil.date();SimpleDateFormat fmt = new SimpleDateFormat("yyyy-MM-dd HH:mm");Date lastExecuteDate = fmt.parse(lastExecuteDateStr);for (int i = 0; ; ++i) {lastExecuteDate = parser.nextDate(lastExecuteDate);if (DateUtil.compare(lastExecuteDate,date)>0) {System.out.println(fmt.format(lastExecuteDate));break;}System.out.println(fmt.format(lastExecuteDate));}}
}class CronRange {private Set<Integer> range = new TreeSet<>();private Integer cycle;private Integer max = null;private Integer min = null;private Boolean returnAll = false;public CronRange range(int start, int end) {for (int i = start; i <= end; ++i) {this.addRange(i);}return this;}public CronRange addRange(int value) {max = (max == null || value > max) ? value : max;min = (min == null || value < min) ? value : min;this.range.add(value);return this;}public Set<Integer> getRange() {return range;}public void setCycle(Integer cycle) {this.cycle = cycle;}public boolean inRange(int value) {return returnAll ? true : range.contains(value);}public boolean isEmpty() {return !returnAll && range.isEmpty();}public Integer getNextValue(int lastValue) {Integer value = null;if (this.cycle != null) {value = this.cycle + lastValue;while (!inRange(value)) {value = value + this.cycle;if (value > max) {value = null;break;}}} else {value = this.getNextMin(lastValue);}return value;}private Integer getNextMin(int value) {Integer[] integers = range.toArray(new Integer[range.size()]);Integer minValue = null;for (int i = 0; i < integers.length; ++i) {if (integers[i] > value) {minValue = integers[i];break;}}return minValue;}public Boolean isAll() {return returnAll;}public void setReturnAll(Boolean returnAll) {this.returnAll = returnAll;}public Integer getMin() {return min;}
}

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Cron 表达式解析，crontab表达式解析

Cron 表达式解析，crontab表达式解析

目录

前言

一、代码展示

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