java把日期转化为cron表达式

java 中，如何把日期（时间点，不是时间段）转化为cron表达式呢？

我觉得这个功能是很常用的，结果在网上竟然没有找到，真实奇怪了？！

直接给代码：

 

/***
	 * 
	 * @param date
	 * @param dateFormat : e.g:yyyy-MM-dd HH:mm:ss
	 * @return
	 */
	public static String formatDateByPattern(Date date,String dateFormat){
		SimpleDateFormat sdf = new SimpleDateFormat(dateFormat);
		String formatTimeStr = null;
		if (date != null) {
			formatTimeStr = sdf.format(date);
		}
		return formatTimeStr;
	}
/***
	 * convert Date to cron ,eg.  "0 06 10 15 1 ? 2014"
	 * @param date  : 时间点
	 * @return
	 */
	public static String getCron(java.util.Date  date){
		String dateFormat="ss mm HH dd MM ? yyyy";
		return formatDateByPattern(date, dateFormat);
	}

 测试：

 

 

@Test
	public void test_getCron(){
		String cron=TimeHWUtil.getCron(new Date());
		System.out.println(cron);
	}

 运行结果：

 

 

关于cron，请参阅：http://www.quartz-scheduler.org/documentation/quartz-2.2.x/tutorials/crontrigger

Format

A cron expression is a string comprised of 6 or 7 fields separated by white space. Fields can contain any of the allowed values, along with various combinations of the allowed special characters for that field. The fields are as follows:

Field Name Mandatory Allowed Values Allowed Special Characters

Seconds	YES	0-59	, - * /
Minutes	YES	0-59	, - * /
Hours	YES	0-23	, - * /
Day of month	YES	1-31	, - * ? / L W
Month	YES	1-12 or JAN-DEC	, - * /
Day of week	YES	1-7 or SUN-SAT	, - * ? / L #
Year	NO	empty, 1970-2099	, - * /

So cron expressions can be as simple as this: * * * * ? *

or more complex, like this: 0/5 14,18,3-39,52 * ? JAN,MAR,SEP MON-FRI 2002-2010

 

Examples

Here are some full examples:

**Expression**	**Meaning**
0 0 12 * * ?	Fire at 12pm (noon) every day
0 15 10 ? * *	Fire at 10:15am every day
0 15 10 * * ?	Fire at 10:15am every day
0 15 10 * * ? *	Fire at 10:15am every day
0 15 10 * * ? 2005	Fire at 10:15am every day during the year 2005
0 * 14 * * ?	Fire every minute starting at 2pm and ending at 2:59pm, every day
0 0/5 14 * * ?	Fire every 5 minutes starting at 2pm and ending at 2:55pm, every day
0 0/5 14,18 * * ?	Fire every 5 minutes starting at 2pm and ending at 2:55pm, AND fire every 5 minutes starting at 6pm and ending at 6:55pm, every day
0 0-5 14 * * ?	Fire every minute starting at 2pm and ending at 2:05pm, every day
0 10,44 14 ? 3 WED	Fire at 2:10pm and at 2:44pm every Wednesday in the month of March.
0 15 10 ? * MON-FRI	Fire at 10:15am every Monday, Tuesday, Wednesday, Thursday and Friday
0 15 10 15 * ?	Fire at 10:15am on the 15th day of every month
0 15 10 L * ?	Fire at 10:15am on the last day of every month
0 15 10 L-2 * ?	Fire at 10:15am on the 2nd-to-last last day of every month
0 15 10 ? * 6L	Fire at 10:15am on the last Friday of every month
0 15 10 ? * 6L	Fire at 10:15am on the last Friday of every month
0 15 10 ? * 6L 2002-2005	Fire at 10:15am on every last friday of every month during the years 2002, 2003, 2004 and 2005
0 15 10 ? * 6#3	Fire at 10:15am on the third Friday of every month
0 0 12 1/5 * ?	Fire at 12pm (noon) every 5 days every month, starting on the first day of the month.
0 11 11 11 11 ?	Fire every November 11th at 11:11am.

Pay attention to the effects of '?' and '*' in the day-of-week and day-of-month fields!