How to Use Cron Expression in Spring Boot for Scheduled Tasks

In Spring Boot, use the @Scheduled annotation with the cron attribute to run tasks on a schedule defined by a cron expression. Enable scheduling by adding @EnableScheduling to a configuration class. The cron expression defines when the method runs, like every minute or at specific times.

Syntax

The cron expression in Spring Boot uses six fields separated by spaces: second, minute, hour, day of month, month, day of week. Each field can have specific values or special characters to define the schedule.

• second: 0-59
• minute: 0-59
• hour: 0-23
• day of month: 1-31
• month: 1-12 or JAN-DEC
• day of week: 0-7 or SUN-SAT (0 and 7 both mean Sunday)

Example: "0 0 12 * * ?" means every day at 12:00 PM.

java

@Scheduled(cron = "0 0 12 * * ?")
public void runAtNoon() {
    // task code here
}

Example

This example shows a Spring Boot component that prints a message every 10 seconds using a cron expression.

java

import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;

import java.time.LocalTime;

@Component
@EnableScheduling
public class ScheduledTask {

    @Scheduled(cron = "*/10 * * * * *")
    public void printEveryTenSeconds() {
        System.out.println("Task executed at: " + LocalTime.now());
    }
}

Output

Task executed at: 10:00:10.123
Task executed at: 10:00:20.124
Task executed at: 10:00:30.125
... (every 10 seconds)

Common Pitfalls

• Forgetting to add @EnableScheduling in a configuration class disables scheduling.
• Using a 5-field cron expression instead of 6 fields causes errors; Spring requires 6 fields.
• Misunderstanding the day of week and day of month fields can cause unexpected schedules; use ? in one of these fields if you don't want to specify it.
• Time zone differences can affect when the task runs; specify time zone if needed with zone attribute.

java

/* Wrong: 5 fields, missing seconds */
@Scheduled(cron = "0 0 12 * *")
public void wrongSchedule() {}

/* Right: 6 fields with seconds */
@Scheduled(cron = "0 0 12 * * ?")
public void correctSchedule() {}

Quick Reference

Field	Allowed Values	Description
Seconds	0-59	Seconds within a minute
Minutes	0-59	Minutes within an hour
Hours	0-23	Hours within a day
Day of Month	1-31	Day of the month
Month	1-12 or JAN-DEC	Month of the year
Day of Week	0-7 or SUN-SAT	Day of the week (0 and 7 = Sunday)

Key Takeaways

Use @Scheduled with a 6-field cron expression to schedule tasks in Spring Boot.

Always add @EnableScheduling to enable scheduled tasks.

Use '?' in either day-of-month or day-of-week to avoid conflicts.

Specify time zone if your schedule depends on a particular zone.

Test cron expressions carefully to ensure correct timing.