Spring Boot uses the @scheduled timer task

Summary: Spring boot uses the @scheduled timer task

Assuming we've set up a spring-based boot project, we'll start by setting the Enable Timer task feature @enablescheduling in application.

start a scheduled task

Package com. scheduling;import org. springframework. Boot. Springapplication;import org. springframework. Boot. autoconfigure. Springbootapplication;import org. springframework. scheduling. annotation. enablescheduling; @SpringBootApplication  @EnableScheduling public  class application {public  static void main (string[] args) throws Exception { Springapplication.run (Application.class);}}       

The role of @EnableScheduling annotations is to discover the task of annotation @scheduled and execute it in the background.

specific implementation classes for timed tasks

Next, let's create a timed task.

Package com. Scheduler. Utils;Import Java. text. SimpleDateFormat;Import Java. util. Date;import org. springframework. scheduling. annotation. scheduled;import org. springframework. stereotype. Component;@ComponentPublicClassscheduler{PrivateStaticFinal SimpleDateFormat DateFormat =New SimpleDateFormat ("HH:Mm:ss ");Executes every 2 seconds@Scheduled (fixedrate =2000)public void testtasks () {System.out< Span class= "Hljs-selector-class" >.println ( "timed Task Execution Time:" + dateformat.format (new Date ())); } //daily 3:05 perform  @Scheduled (cron = Span class= "hljs-string" > "0 05 03? * * ") public void testtasks () {System.out.println (" timed Task Execution Time: "+ Dateformat.format ( new Date ())); }} 

Run spring Boot, the output is as follows, and the current time is printed every 2 seconds.

定时任务执行时间：23:28:00定时任务执行时间：23:28:02定时任务执行时间：23:28:04定时任务执行时间：23:28:06定时任务执行时间：23:28:08

Note: you need to add a comment to the class on the scheduled task: @Component, add a comment @scheduled to the specific timed task method to start the scheduled task.

@Scheduled Parameter Description

• @Scheduled (fixedrate=3000): Executes again 3 seconds after the last execution time point;
• @Scheduled (fixeddelay=3000): The last execution time point 3 seconds to execute again;
• @Scheduled (initialdelay=1000, fixeddelay=3000): The first delay is 1 seconds , and then 3 seconds after the last execution time . implemented again;
• @Scheduled (cron= "* * * * * *?") : Executes according to cron rules;

Cron Rules

Each time element in a cron expression is split with spaces , and the expression has at least 6 (or perhaps 7) of the following meanings:

• Seconds (0~59)
• Minutes (0~59)
• Hours (0~23)
• Days (months) (0~31, but you need to consider the number of days of your month)
• Month (0~11)
• Days (weeks) (1~7 1=sun or Sun,mon,tue,wed,thu,fri,sat)
• 7. Year (1970-2099)

Each of these elements can be a value (such as 6), a continuous interval (9-12), a time interval (8-18/4) (/= every 4 hours), a list (1,3,5), and a wildcard character. Because the "date in the month" and "date in the week" are mutually exclusive, one of the two elements must be set.

• 0 0 10,14,16 * *? 10 o'clock in the morning, 2 o'clock in the afternoon, 4 O ' Day
• 0 0/30 9-17 * *? Every half hour for nine to five working hours
• 0 0 12? * WED means every Wednesday noon 12 o'clock
• "0 0 12 * *?" trigger 12 o'clock noon every day.
• "0 15 10?" * * "trigger 10:15 every day"
• "0 15 10 * *?" Daily 10:15 Trigger
• "0 15 10 * *?" * "10:15 per day" trigger
• "0 15 10 * *?" 2005 "2005-year daily 10:15 Trigger
• "0 * 14 * *?" triggers every 1 minutes from 2 o'clock in the afternoon to 2:59 daily
• "0 0/5 14 * *?" triggers every 5 minutes from 2 o'clock in the afternoon to 2:55 daily
• "0 0/5 14,18 * *?" triggers every 5 minutes from 2 o'clock in the afternoon to 2:55 daily and from 6 o'clock in the afternoon to 6:55
• "0 0-5 14 * *?" triggers every 1 minutes from 2 o'clock in the afternoon to 2:05 daily
• "0 10,44 14?" 3 WED "2:10 and 2:44 triggers in Wednesday of every March
• "0 15 10?" * Mon-fri "Monday to Friday 10:15 trigger
• "0 15 10 15 *?" 15th 10:15 per month
• "0 L *?" 10:15 on the last day of the month
• "0 15 10?" * 6L "Last month of Friday 10:15 Trigger
• "0 15 10?" * 6L 2002-2005 "2002 to 2005 the last of the monthly Friday 10:15 trigger
• "0 15 10?" * 6#3 "Monthly third Friday 10:15 trigger

Some sub-expressions can contain ranges or lists

The "*" character represents all possible values

Therefore, "*" in the sub-expression ( month ) represents the meaning of each month, "*" in the subexpression ( Day (week)) represents every day of the week

The "/" character is used to specify the increment of the numeric value

For example: "0/15" in sub-expressions (minutes) means starting from the No. 0 minute, every 15 minutes

"3/20" in the sub-expression (minutes) means that every 20 minutes (it is the same as "3,23,43") starting from the 3rd minute

“？ "Character is used only for days (months) and days (weeks) of two sub-expressions, indicating that no value is specified

When one of the 2 sub-expressions is assigned a value, in order to avoid a conflict, you need to set the value of another subexpression to "? ”

The "L" character is used only for days (months) and days (weeks) of two sub-expressions, which is the abbreviation for the word "last"

But it has a different meaning in two sub-expressions.

• In the day (month) subexpression, "L" represents the last day of the one-month
• In the day (week) Self-expression, "L" represents the last day of one weeks, the SAT
• If there is something specific before "L", it has other meanings.
• For example: "6L" means the 6th day of the month, and "Fril" means the last Friday of the month.
• Note: When using the "L" parameter, do not specify a list or range, as this can cause problems

Field	Allowed values	Allowed special characters
Seconds	0-59	, - * /
Score of	0-59	, - * /
Hours	0-23	, - * /
Date	January 31	, - * ? /L W C
Month	1-12 or Jan-dec	, - * /
Week	1-7 or Sun-sat	, - * ? /L C #
Year (optional)	Leave Blank, 1970-2099

Spring Boot uses the @scheduled timer task