Implementing Dynamic Scheduled Tasks in Spring Boot

Previously a static scheduled task using cron expressions was described, but it required predefined configuration and could not be changed at runtime.

This article shows how to implement dynamic scheduled tasks in a Spring Boot project.

First, the required Maven dependencies are added (spring-boot-starter-web, spring-boot-starter-log4j2, spring-boot-starter-validation, lombok).

The main application class is annotated with @EnableScheduling and starts the Spring Boot application.

The server port is configured in application.yml , and the cron expression is stored in task-config.ini (e.g., printTime.cron=0/10 * * * * ? ).

A task class implements SchedulingConfigurer , reads the cron value with @Value("${printTime.cron}") , and registers a trigger task that uses a CronTrigger to determine the next execution time, allowing the cron expression to be changed at runtime.

A REST controller provides an endpoint /test/updateCron that receives a new cron string, updates the task’s cron field, and returns “ok”. After restarting the application, the task runs according to the new schedule (e.g., every 15 seconds).

For scenarios where a fixed‑interval trigger is preferred, the article replaces CronTrigger with PeriodicTrigger , which accepts a millisecond interval ( timer ) and adds another endpoint /test/updateTimer to modify this interval dynamically.

Running the application and invoking the endpoints demonstrates that the scheduled task can be switched between cron‑based and period‑based execution without restarting the service.