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This guide walks you through the steps for scheduling tasks with Spring.
== What you'll build
You'll build an application that prints out the current time every five seconds using Spring's `@Scheduled` annotation.
== What you'll need
:java_version: 1.8
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== Create a scheduled task
Now that you've set up your project, you can create a scheduled task.
`src/main/java/hello/ScheduledTasks.java`
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The `Scheduled` annotation defines when a particular method runs.
NOTE: This example uses `fixedRate`, which specifies the interval between method invocations measured from the start time of each invocation. There are https://docs.spring.io/spring/docs/{spring_version}/spring-framework-reference/html/scheduling.html#scheduling-annotation-support-scheduled[other options], like `fixedDelay`, which specifies the interval between invocations measured from the completion of the task. You can also https://docs.spring.io/spring/docs/{spring_version}/javadoc-api/org/springframework/scheduling/support/CronSequenceGenerator.html[use `@Scheduled(cron=". . .")` expressions for more sophisticated task scheduling].
== Enable Scheduling
Although scheduled tasks can be embedded in web apps and WAR files, the simpler approach demonstrated below creates a standalone application. You package everything in a single, executable JAR file, driven by a good old Java `main()` method.
`src/main/java/hello/Application.java`
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https://docs.spring.io/spring/docs/current/spring-framework-reference/htmlsingle/#scheduling-enable-annotation-support[`@EnableScheduling`] ensures that a background task executor is created. Without it, nothing gets scheduled.
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Logging output is displayed and you can see from the logs that it is on a background thread. You should see your scheduled task fire every 5 seconds:
....
[...]
2016-08-25 13:10:00.143 INFO 31565 --- [pool-1-thread-1] hello.ScheduledTasks : The time is now 13:10:00
2016-08-25 13:10:05.143 INFO 31565 --- [pool-1-thread-1] hello.ScheduledTasks : The time is now 13:10:05
2016-08-25 13:10:10.143 INFO 31565 --- [pool-1-thread-1] hello.ScheduledTasks : The time is now 13:10:10
2016-08-25 13:10:15.143 INFO 31565 --- [pool-1-thread-1] hello.ScheduledTasks : The time is now 13:10:15
....
== Summary
Congratulations! You created an application with a scheduled task. Heck, the actual code was shorter than the build file! This technique works in any type of application.
== See Also
The following guides may also be helpful:
* https://spring.io/guides/gs/spring-boot/[Building an Application with Spring Boot]
* https://spring.io/guides/gs/batch-processing/[Creating a Batch Service]
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