Learn about scheduled tasks in one article

What is a scheduled task ？

Timing task , A brief description is to trigger the execution of an action within a specified time . Similar to us tonight 12 I want to buy something , Then you need to set an alarm clock to remind you , Tell you 12 Point you need to buy something , This alarm clock reminds you regularly , It's a scheduled task .

Application scenarios for scheduled tasks

Place the order ：30 Realize the payment function within minutes .
Place the order ： Start a timed mission ; Whether to pay , payment , Order fulfillment ; No payment , Cancellation of order .
database ： Clean up regularly , Statistics .

Use Schedule Achieve timed tasks

Cron An expression is a string , String to 5 or 6 Space between , It is divided into 6 or 7 Domains , Every time
A domain represents a meaning ,Cron There are two grammatical formats as follows ：
（1） Seconds Minutes Hours DayofMonth Month DayofWeek Year
（2）Seconds Minutes Hours DayofMonth Month DayofWeek

Example

@Configuration
@EnableScheduling
public class MyJobTest {
    
@Scheduled(cron="0/2 * * * * *")
public void task(){
    
System.out.println(" Time :"+
LocalDateTime.now());
}
}

Use quartz Achieve timed tasks

1、 introduce jar

<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starterquartz</artifactId>
</dependency>