Overview

Maven Coordinates

To enable Scheduling add the following dependency to your project’s pom.xml (see Managing Dependencies).

<dependency>
    <groupId>io.helidon.microprofile.scheduling</groupId>
    <artifactId>helidon-microprofile-scheduling</artifactId>
</dependency>

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Scheduling

For scheduling tasks in Helidon you can choose from @Scheduled or @FixedRate annotations by required complexity of invocation interval. All you need is define method with one of the annotations in application scoped bean.

Fixed rate

For simple fixed rate invocation interval is @FixedRate the easiest way for scheduling task invocation.

Example of scheduling with fixed rate

@FixedRate(initialDelay = 5, value = 10, timeUnit = TimeUnit.MINUTES)
public void methodName() {
    System.out.println("Every 10 minutes, first invocation 5 minutes after start");
}

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All values defined with the annotation can be overridden from the config.

Overiding annotated values from config

fully.quallified.ClassName.methodName:
  schedule:
    initial-delay: 5
    delay: 15
    time-unit: HOURS

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Metadata like human-readable interval description or configured values are available through FixedRateInvocation injected as method parameter.

Example with ivocation metadata

@FixedRate(initialDelay = 5, value = 10, timeUnit = TimeUnit.MINUTES)
public void methodName(FixedRateInvocation inv) {
    System.out.println("Method invoked " + inv.description());
}

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Cron expression

For more complicated interval definition, cron expression can be leveraged with @Schedule annotation.

Example of scheduling with cron expression

@Scheduled("0 15 8 ? * *", concurrentExecution = false)
public void methodName() {
    System.out.println("Executer every day at 8:15");
}

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Cron expression format

<seconds> <minutes> <hours> <day-of-month> <month> <day-of-week> <year>

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Cron expression fields

Order	Name	Supported values	Supported field format	Optional
1	seconds	0-59	CONST, LIST, RANGE, WILDCARD, INCREMENT	false
2	minutes	0-59	CONST, LIST, RANGE, WILDCARD, INCREMENT	false
3	hours	0-23	CONST, LIST, RANGE, WILDCARD, INCREMENT	false
4	day-of-month	1-31	CONST, LIST, RANGE, WILDCARD, INCREMENT, ANY, LAST, WEEKDAY	false
5	month	1-12 or JAN-DEC	CONST, LIST, RANGE, WILDCARD, INCREMENT	false
6	day-of-week	1-7 or SUN-SAT	CONST, LIST, RANGE, WILDCARD, INCREMENT, ANY, NTH, LAST	false
7	year	1970-2099	CONST, LIST, RANGE, WILDCARD, INCREMENT	true

Field formats

Name	Regex format	Example	Description
CONST	\d+	12	exact value
LIST	\d+,\d+(,\d+)*	1,2,3,4	list of constants
RANGE	\d+-\d+	15-30	range of values from-to
WILDCARD	\*	*	all values withing the field
INCREMENT	\d+\/\d+	0/5	inital number / increments, 2/5 means 2,7,9,11,16,…
ANY	\?	?	any day(apply only to day-of-week and day-of-month)
NTH	\#	1#3	nth day of the month, 2#3 means third monday of the month
LAST	\d*L(+\d+\|\-\d+)?	3L-3	last day of the month in day-of-month or last nth day in the day-of-week
WEEKDAY	\#	1#3	nearest weekday of the nth day of month, 1W is the first monday of the week

Examples

Cron expression	Description
* * * * * ?	Every second
0/2 * * * * ? *	Every 2 seconds
0 45 9 ? * *	Every day at 9:45
0 15 8 ? * MON-FRI	Every workday at 8:15

Metadata like human-readable interval description or configured values are available through CronInvocation injected as method parameter.

Example with invocation metadata

@Scheduled("0 15 8 ? * *")
public void methodName(CronInvocation inv) {
    System.out.println("Method invoked " + inv.description());
}

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Scheduled annotation properties can be overridden using application.yaml properties

Overriding annotated values from config

fully.quallified.ClassName.methodName:
  schedule:
    cron: "* * * * * ?"
    concurrent: false

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Configuration properties

Property	Description
cron	String containing cron setup
concurrent	Boolean, equivalent `concurrentExecution` property of `@Scheduled`. Default `true`.