Introduction
Spring Boot provides annotation support for task scheduling. It is easy way to develop and run a Task scheduler without using any xml and bean configurations Simply add the annotation @Scheduled on the task scheduler method with required interval time. In this example, we will see how to use Spring @Scheduledannotation to schedule a task.
Enable scheduling annotations
To enable support for @Scheduled annotation add @EnableScheduling to one of your @Configuration classes:
| @Configuration | |
| @EnableScheduling | |
| public class AppConfig { | |
| } |
You are free to pick and choose the relevant annotations for your application. For example, for more fine-grained control you can additionally implement the SchedulingConfigurer interfaces.
The @Scheduled annotation
The @Scheduled annotation can be added to a method along with trigger metadata.
Important: The simple rules that need to be followed to annotate a method with @Scheduled are:
-
A method should not accept any parameters
-
A method should have void return type
For example, the following method would be invoked every 5 seconds with a fixed delay, meaning that the period will be measured from the completion time of each preceding invocation.
| @Scheduled(fixedDelay=5000) | |
| public void doSomething() { | |
| // something that should execute periodically | |
| } |
If a fixed rate execution is desired, simply change the property name specified within the annotation.
The following would be executed every 5 seconds measured between the successive start times of each invocation.
| @Scheduled(fixedRate=5000) | |
| public void doSomething() { | |
| // something that should execute periodically | |
| } |
For fixed-delay and fixed-rate tasks, an initial delay may be specified indicating the number of milliseconds to wait before the first execution of the method.
| @Scheduled(initialDelay=1000, fixedRate=5000) | |
| public void doSomething() { | |
| // something that should execute periodically | |
| } |
If simple periodic scheduling is not expressive enough, then a cron expression may be provided. For example, the following will only execute on weekdays.
| @Scheduled(cron="*/5 * * * * MON-FRI") | |
| public void doSomething() { | |
| // something that should execute on weekdays only | |
| } |