java * 和 ? 之间的区别 在春天@Scheduled(cron=".....")
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Difference between * and ? in Spring @Scheduled(cron=".....")
提问by Jordan
I've been looking at the Spring Boot example for scheduling tasks (https://spring.io/guides/gs/scheduling-tasks/) and reading through some documentation (https://javahunter.wordpress.com/2011/05/05/cronscheduler-in-spring/) and I see that * and ? are used almost interchangeably.
我一直在查看用于调度任务的 Spring Boot 示例（https://spring.io/guides/gs/scheduling-tasks/）并阅读一些文档（https://javahunter.wordpress.com/2011/05 /05/cronscheduler-in-spring/) 我看到 * 和 ? 几乎可以互换使用。
For example, the line
例如，线
@Scheduled(cron = "0 15 10 ? * *")
and
和
@Scheduled(cron = "0 15 10 * * ?")
do the exact same thing. So what is the difference between * and ?
做完全相同的事情。那么 * 和 之间有什么区别？
采纳答案by Jens
asterix stands for all possible values. question marks should be used for non specific value
星号代表所有可能的值。问号应用于非特定值
*("all values") - used to select all values within a field. For example, "" in the minute field means *"every minute".
? ("no specific value") - useful when you need to specify something in one of the two fields in which the character is allowed, but not the other. For example, if I want my trigger to fire on a particular day of the month (say, the 10th), but don't care what day of the week that happens to be, I would put "10" in the day-of-month field, and "?" in the day-of-week field. See the examples below for clarification.
*("all values") - 用于选择字段中的所有值。例如，分钟字段中的“”表示*“每分钟”。
? （“无特定值”） - 当您需要在允许字符的两个字段之一中指定某些内容时很有用，而另一个字段则不允许。例如，如果我希望我的触发器在一个月的某一天（比如 10 号）触发，但不关心那一天是一周中的哪一天，我会将“10”放在当天-month 字段和“？” 在星期字段中。请参阅下面的示例以进行说明。
Copied from the tutorial
复制自教程
回答by Luchostein
The tutorial is outdated. The symbol ?means exactlythe same than *. As of Spring 3.1.2.RELEASE, the call hierarchy is:
教程已经过时了。符号?是指恰好比相同*。从 Spring 3.1.2.RELEASE 开始，调用层次结构是：
The constructor CronTrigger(String)calls the constructor CronSequenceGenerator(String)which calls parse(String)which calls setDays(BitSet bits, String field, int max). Its implementation is clear:
构造函数CronTrigger(String)调用CronSequenceGenerator(String)调用parse(String)which的构造函数setDays(BitSet bits, String field, int max)。它的实现很明确：
private void setDays(BitSet bits, String field, int max) {
if (field.contains("?")) {
field = "*";
}
setNumberHits(bits, field, 0, max);
}
So, if ?, then *.
所以，如果?，那么*。
