tags	projects
scheduling	spring-framework

Table of Contents

• What you’ll build
• What you’ll need
• Create a scheduled task
• Enable Scheduling
• Summary

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

https://raw.githubusercontent.com/spring-guides/getting-started-macros/master/prereq_editor_jdk_buildtools.adoc

https://raw.githubusercontent.com/spring-guides/getting-started-macros/master/how_to_complete_this_guide.adoc

https://raw.githubusercontent.com/spring-guides/getting-started-macros/master/hide-show-gradle.adoc

https://raw.githubusercontent.com/spring-guides/getting-started-macros/master/hide-show-maven.adoc

https://raw.githubusercontent.com/spring-guides/getting-started-macros/master/hide-show-sts.adoc

Create a scheduled task

Now that you’ve set up your project, you can create a scheduled task.

src/main/java/hello/ScheduledTasks.java

link:complete/src/main/java/hello/ScheduledTasks.java[role=include]

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 other options, like fixedDelay, which specifies the interval between invocations measured from the completion of the task. You can also 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

link:complete/src/main/java/hello/Application.java[role=include]

@SpringBootApplication is a convenience annotation that adds all of the following:

• @Configuration tags the class as a source of bean definitions for the application context.

• @EnableAutoConfiguration tells Spring Boot to start adding beans based on classpath settings, other beans, and various property settings. Technically, Spring Boot doesn’t have anything to auto-configure when it comes to scheduling but a future version might.

• @ComponentScan tells Spring to look for other components, configurations, and services in the the hello package, allowing it to find the ScheduledTasks.

The main() method uses Spring Boot’s SpringApplication.run() method to launch an application. Did you notice that there wasn’t a single line of XML? This application is 100% pure Java and you didn’t have to deal with configuring any plumbing or infrastructure.

@EnableScheduling ensures that a background task executor is created. Without it, nothing gets scheduled.

https://raw.githubusercontent.com/spring-guides/getting-started-macros/master/build_an_executable_jar_subhead.adoc

https://raw.githubusercontent.com/spring-guides/getting-started-macros/master/build_an_executable_jar_with_both.adoc

Logging output is displayed. You should see your scheduled task fire every 5 seconds:

[...]
The time is now 13:10:00
The time is now 13:10:05
The time is now 13:10:10
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.

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