Cron expressions for scheduling in Spring Boot

Introduction

Cron expressions help you tell your Spring Boot app when to run tasks automatically. They use simple codes to set times and dates.

Run a report every day at 8 AM without manual work.

Send reminder emails every Monday morning.

Clean up temporary files every hour.

Backup data every night at midnight.

Check system health every 5 minutes.

Syntax

Spring Boot

second minute hour day-of-month month day-of-week year(optional)

Each part is a number or symbol that means when to run.

Use * to mean 'every' for that part, like every minute or every day.

Examples

Run at 8:00 AM every day.

Spring Boot

0 0 8 * * ?

Run at 10:15 AM every weekday (Monday to Friday).

Spring Boot

0 15 10 ? * MON-FRI

Run every 5 minutes during 2 PM and 6 PM every day.

Spring Boot

0 0/5 14,18 * * ?

Run at midnight on January 1st every year.

Spring Boot

0 0 0 1 1 ?

Sample Program

This Spring Boot component runs two tasks automatically. One runs daily at 8 AM, the other runs at 10:15 AM Monday to Friday. The @Scheduled annotation uses cron expressions to set the times.

Spring Boot

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

@Component
public class ScheduledTasks {

    @Scheduled(cron = "0 0 8 * * ?")
    public void runDailyTask() {
        System.out.println("Task runs every day at 8 AM");
    }

    @Scheduled(cron = "0 15 10 ? * MON-FRI")
    public void runWeekdayTask() {
        System.out.println("Task runs at 10:15 AM on weekdays");
    }
}

Important Notes

Use '?' in day-of-month or day-of-week to say 'no specific value' when you specify the other.

Seconds are required in Spring cron expressions, unlike some other cron systems.

Test your cron expressions with online tools to avoid mistakes.

Summary

Cron expressions tell Spring Boot when to run tasks automatically.

They use 6 or 7 parts: seconds, minutes, hours, day, month, weekday, and optional year.

Use @Scheduled annotation with cron to schedule methods easily.