# gs-scheduling-tasks

**Repository Path**: nicehoney/gs-scheduling-tasks

## Basic Information

- **Project Name**: gs-scheduling-tasks
- **Description**: No description available
- **Primary Language**: Unknown
- **License**: Apache-2.0
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2021-01-12
- **Last Updated**: 2021-01-12

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

:toc:
:spring_version: current
:icons: font
:source-highlighter: prettify
:project_id: gs-scheduling-tasks

This guide walks you through the steps for scheduling tasks with Spring.

== What You Will Build

You will build an application that prints out the current time every five seconds by using
Spring's `@Scheduled` annotation.

== What You Need

:java_version: 1.8
include::https://raw.githubusercontent.com/spring-guides/getting-started-macros/master/prereq_editor_jdk_buildtools.adoc[]

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

[[scratch]]
== Starting with Spring Initializr

For all Spring applications, you should start with the https://start.spring.io[Spring
Initializr]. The Initializr offers a fast way to pull in all the dependencies you need for
an application and does a lot of the setup for you. This example needs no Spring
dependencies. Spring Boot itself provides all the Spring packages that you need for this
guide.

The following listing shows the `pom.xml` file that is created when you choose Maven:

====
[source,xml]
----
include::initial/pom.xml[]
----
====

The following listing shows the `build.gradle` file that is created when you choose Gradle:

====
[source,text]
----
include::initial/build.gradle[]
----
====

=== Adding the `awaitility` Dependency

The tests in
`complete/src/test/java/com/example/schedulingtasks/ScheduledTasksTest.java`
require the `awaitility` library.

NOTE: Later versions of the `awaitility` library do not work for this test, so you have to
specify version 3.1.2.

To add the `awaitility` library to Maven, add the following dependency:

====
[source,xml]
----
<dependency>
  <groupId>org.awaitility</groupId>
  <artifactId>awaitility</artifactId>
  <version>3.1.2</version>
  <scope>test</scope>
</dependency>
----
====

The following listing shows the finished `pom.xml` file:

====
[source,xml]
----
include::complete/pom.xml[]
----
====

To add the `awaitility` library to Gradle, add the following dependency:

====
[source,text]
----
	testImplementation 'org.awaitility:awaitility:3.1.2'
----
====

The following listing shows the finished `build.gradle` file:

====
[source,xml]
----
include::complete/build.gradle[]
----
====

[[initial]]
== Create a Scheduled Task

Now that you have set up your project, you can create a scheduled task. The following
listing (from `src/main/java/com/example/schedulingtasks/ScheduledTasks.java`) shows how
to do so:

====
[source,java]
----
include::complete/src/main/java/com/example/schedulingtasks/ScheduledTasks.java[]
----
====

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],
such as `fixedDelay`, which specifies the interval between invocations measured from the
completion of the task. You can also use https://docs.spring.io/spring/docs/{spring_version}/javadoc-api/org/springframework/scheduling/support/CronSequenceGenerator.html[`@Scheduled(cron=". . .")`]
expressions for more sophisticated task scheduling.

== Enable Scheduling

Although scheduled tasks can be embedded in web applications and WAR files, the simpler
approach (shown in the next listing) creates a standalone application. To do so,
package everything in a single, executable JAR file, driven by a good old Java `main()`
method. The following listing (from
`src/main/java/com/example/schedulingtasks/SchedulingTasksApplication.java`) shows the
application class:

====
[source,java]
----
include::complete/src/main/java/com/example/schedulingtasks/SchedulingTasksApplication.java[]
----
====

include::https://raw.githubusercontent.com/spring-guides/getting-started-macros/master/spring-boot-application-new-path.adoc[]

The
https://docs.spring.io/spring/docs/current/spring-framework-reference/htmlsingle/#scheduling-enable-annotation-support[`@EnableScheduling`]
annotation ensures that a background task executor is created. Without it, nothing gets
scheduled.

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

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

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 five seconds. The following listing
shows typical output:

====
[source,text]
----
...
2019-10-02 12:07:35.659  INFO 28617 --- [   scheduling-1] c.e.schedulingtasks.ScheduledTasks       : The time is now 12:07:35
2019-10-02 12:07:40.659  INFO 28617 --- [   scheduling-1] c.e.schedulingtasks.ScheduledTasks       : The time is now 12:07:40
2019-10-02 12:07:45.659  INFO 28617 --- [   scheduling-1] c.e.schedulingtasks.ScheduledTasks       : The time is now 12:07:45
2019-10-02 12:07:50.657  INFO 28617 --- [   scheduling-1] c.e.schedulingtasks.ScheduledTasks       : The time is now 12:07:50
...
----
====

== Summary

Congratulations! You created an application with a scheduled task. Also, 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]

include::https://raw.githubusercontent.com/spring-guides/getting-started-macros/master/footer.adoc[]