CronTriggers are often more useful than SimpleTrigger, if you need a job-firing schedule that recurs based on calendar-like notions, rather than on the exactly specified intervals of SimpleTrigger.
CronTriggers 比SimpleTrigger经常更加有用,如果你需要一个基于像日历概念的重复 job-firing 调度，而不是在一个SimpleTrigger特定的间隔。

With CronTrigger, you can specify firing-schedules such as "every Friday at noon", or "every weekday and 9:30 am", or even "every 5 minutes between 9:00 am and 10:00 am on every Monday, Wednesday and Friday".
使用CronTrigger,你可以限定firing-schedulers例如 “每天中午“，或者”，”每天周日上午9:30“，或者甚至 “每5分钟在上午9：00 到 10：00 每周一、周三、周五”

Cron Expressions
Cron 表达式

Cron-Expressions are used to configure instances of CronTrigger. Cron-Expressions are strings that are actually made up of six sub-expressions, that describe individual details of the schedule. These sub-expression are separated with white-space, and represent:
Cron 表达式被用来注册CronTrigger实例的。Cron表达式是字符串，它由六个子表达式组成，它描述了不同的调度细节。这些子表达式被白色表达式隔开，表现：

Seconds  秒
Minutes  分
Hours    时
Day-of-Month  日
Month         月
Day-of-Week   周

An example of a complete cron-expression is the string "0 0 12 ? * WED" - which means "every Wednesday at 12:00 pm".
一个完整的Cron 表达式例子是字符串“0 0 12 ? * WEB” 意味着每周三上午12：00。

Individual sub-expressions can contain ranges and/or lists. For example, the day of week field in the previous (which reads "WED") example could be replaces with "MON-FRI", "MON, WED, FRI", or even "MON-WED,SAT".
单独的子表达式可以包含平行的 和/或。例如，在上一个例子一周的一天字段（它读作"WED"）可以被“MON-FRI”,"MON,WED,FRI"，或者甚至"MON-WED,SAT"替换掉。

Wild-cards (the '*' character) can be used to say "every" possible value of this field. Therefore the '*' character in the "Month" field of the previous example simply means "every month". A '*' in the Day-Of-Week field would obviously mean "every day of the week".
统配符（"*"字符）可以被用来作为这个字段的"每一个"可能值。所以,在上一个例子月字段中的"*"字符表示每个月。 一个"*"在周天将明显意味着周的每一天。

All of the fields have a set of valid values that can be specified. These values should be fairly obvious - such as the numbers 0 to 59 for seconds and minutes, and the values 0 to 23 for hours. Day-of-Month can be any value 0-31, but you need to be careful about how many days are in a given month! Months can be specified as values between 0 and 11, or by using the strings JAN, FEB, MAR, APR, MAY, JUN, JUL, AUG, SEP, OCT, NOV and DEC. Days-of-Week can be specified as vaules between 1 and 7 (1 = Sunday) or by using the strings SUN, MON, TUE, WED, THU, FRI and SAT.
所有字段都用一个合法限定的值。这些值应该是明显的，例如0到59数字为秒和分的限定，0到23为小时。月的某天可以是0-31的，或者你需要消息给个月有多少天！月份可以被限定在0到11，或者，使用英文字符串缩写。一个礼拜的一天可以被限定作为1到7（1=Sunnday）或者使用英文字符串。

The '/' character can be used to specify increments to values. For example, if you put '0/15' in the Minutes field, it means 'every 15 minutes, starting at minute zero'. If you used '3/20' in the Minutes field, it would mean 'every 20 minutes during the hour, starting at minute three' - or in other words it is the same as specifying '3,23,43' in the Minutes field.
"/"字符可以内用来限定值的增加。例如，如果你将'0/15'放到分钟字段，它意味着"每15分钟，开始于0分钟"。如果你使用"3/20"在分钟字段中，你将意味着"一个小时内每20分钟，开始于3分钟"---  或者换言之，它和在分钟字段"3,23,43"限定是一样的。

The '?' character is allowed for the day-of-month and day-of-week fields. It is used to specify "no specific value". This is useful when you need to specify something in one of the two fields, but not the other. See the examples below (and CronTrigger JavaDOC) for clarification.

"?"字符是允许为月的某一天或者周的某一天字段的。它被用来限定"没有限定值"。这是有用的，当你需要限定一些事情在一个或两个字段中，但不是这里的。

The 'L' character is allowed for the day-of-month and day-of-week fields. This character is short-hand for "last", but it has different meaning in each of the two fields. For example, the value "L" in the day-of-month field means "the last day of the month" - day 31 for January, day 28 for February on non-leap years. If used in the day-of-week field by itself, it simply means "7" or "SAT". But if used in the day-of-week field after another value, it means "the last xxx day of the month" - for example "6L" or "FRIL" both mean "the last friday of the month". When using the 'L' option, it is important not to specify lists, or ranges of values, as you'll get confusing results.

"L"字符是允许用来月某天和周某天字段。这个字符是一个"last"的缩写，但是它有不同的意义在两个字段的其中之一。例如，这个值"L"在月字段的某一天意味着" 这个月的最后一天"，31或者28等等。

Here are a few more examples of expressions and their meanings - you can find even more in the JavaDOC for CronTrigger

CronTrigger Example 1 - an expression to create a trigger that simply fires every 5 minutes

  "0 0/5 * * * ?"

CronTrigger Example 2 - an expression to create a trigger that fires every 5 minutes, at 10 seconds after the minute (i.e. 10:00:10 am, 10:05:10 am, etc.).

  "10 0/5 * * * ?"

CronTrigger Example 3 - an expression to create a trigger that fires at 10:30, 11:30, 12:30, and 13:30, on every Wednesday and Friday.

  "0 30 10-13 ? * WED,FRI"

CronTrigger Example 4 - an expression to create a trigger that fires every half hour between the hours of 8 am and 10 am on the 5th and 20th of every month. Note that the trigger will NOT fire at 10:00 am, just at 8:00, 8:30, 9:00 and 9:30

  "0 0/30 8-9 5,20 * ?"

Note that some scheduling requirements are too complicated to express with a single trigger - such as "every 5 minutes between 9:00 am and 10:00 am, and every 20 minutes between 1:00 pm and 10:00 pm". The solution in this scenario is to simply create two triggers, and register both of them to run the same job.

更多参见http://www.opencms.org/export/javadoc/core/org/opencms/scheduler/CmsScheduledJobInfo.html