Quarkus - Quarkus Extension for Spring Scheduling API

Quarkus - Quarkus Extension for Spring Scheduling API

While users are encouraged to use regular Quarkus scheduler, Quarkus provides a compatibility layer for Spring Scheduled in the form of the spring-scheduled extension.

This guide explains how a Quarkus application can leverage the well known Spring Scheduled annotation to configure and schedule tasks.

This technology is considered preview.

In preview, backward compatibility and presence in the ecosystem is not guaranteed. Specific improvements might require to change configuration or APIs and plans to become stable are under way. Feedback is welcome on our mailing list or as issues in our GitHub issue tracker.

For a full list of possible extension statuses, check our FAQ entry.

Prerequisites

To complete this guide, you need:

less than 15 minutes
an IDE
JDK 1.8+ installed with JAVA_HOME configured appropriately
Apache Maven 3.6.2+
Some familiarity with the Spring Web extension

Solution

We recommend that you follow the instructions in the next sections and create the application step by step. However, you can go right to the completed example.

Clone the Git repository: git clone [https://github.com/quarkusio/quarkus-quickstarts.git](https://github.com/quarkusio/quarkus-quickstarts.git), or download an archive.

The solution is located in the spring-scheduled-quickstart directory.

Creating the Maven project

First, we need a new project. Create a new project with the following command:

mvn io.quarkus:quarkus-maven-plugin:1.7.6.Final:create \
    -DprojectGroupId=org.acme \
    -DprojectArtifactId=spring-scheduler-quickstart \
    -DclassName="org.acme.spring.scheduler.CountResource" \
    -Dpath="/count" \
    -Dextensions="spring-scheduled"
cd spring-scheduler-quickstart

This command generates a Maven project with a REST endpoint and adds the spring-scheduled extension.

If you already have your Quarkus project configured, you can add the spring-scheduled extension to your project by running the following command in your project base directory:

./mvnw quarkus:add-extension -Dextensions="spring-scheduled"

This will add the following to your pom.xml:

<dependency>
    <groupId>io.quarkus</groupId>
    <artifactId>quarkus-spring-scheduled</artifactId>
</dependency>

Creating a scheduled job

In the org.acme.spring.scheduler package, create the CounterBean class, with the following content:

package org.acme.spring.scheduler;
import org.springframework.scheduling.annotation.Scheduled;
import java.util.concurrent.atomic.AtomicInteger;
import javax.enterprise.context.ApplicationScoped;
@ApplicationScoped              (1)
public class CounterBean {
    private AtomicInteger counter = new AtomicInteger();
    public int get() {   (2)
        return counter.get();
    }
    @Scheduled(cron="*/5 * * * * ?")   (3)
    void cronJob() {
        counter.incrementAndGet();      (4)
        System.out.println("Cron expression hardcoded");
    }
    @Scheduled(cron = "{cron.expr}")   (5)
    void cronJobWithExpressionInConfig() {
        counter.incrementAndGet();
        System.out.println("Cron expression configured in application.properties");
    }
    @Scheduled(fixedRate = 1000)    (6)
    void jobAtFixedRate() {
        counter.incrementAndGet();
        System.out.println("Fixed Rate expression");
    }
    @Scheduled(fixedRateString = "${fixedRate.expr}")      (7)
    void jobAtFixedRateInConfig() {
        counter.incrementAndGet();
        System.out.println("Fixed Rate expression configured in application.properties");
    }
}

Declare the bean in the application scope. Spring only detects @Scheduled annotations in beans.
The get() method allows retrieving the current value.
Use the Spring @Scheduled annotation with a cron-like expression to instruct Quarkus to schedule this method run. In this example we’re scheduling a task to be executed at 10:15am every day.
The code is pretty straightforward. Every day at 10:15am, the counter is incremented.
Define a job with a cron-like expression cron.expr which is configurable in application.properties.
Define a method to be executed at a fixed interval of time. The period is expressed in milliseconds.
Define a job to be executed at a fixed interval of time fixedRate.expr which is configurable in application.properties.

Updating the application configuration file

Edit the application.properties file and add the cron.expr and the fixedRate.expr configuration:

# The syntax used by Spring for cron expressions is the same as which is used by regular Quarkus scheduler.
cron.expr=*/5 * * * * ?
fixedRate.expr=1000

Updating the resource and the test

Edit the CountResource class, and update the content to:

package org.acme.spring.scheduler;
import javax.inject.Inject;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
@Path("/count")
public class CountResource {
    @Inject
    CounterBean counter;    (1)
    @GET
    @Produces(MediaType.TEXT_PLAIN)
    public String hello() {
        return "count: " + counter.get();   (2)
    }
}

Inject the CounterBean
Send back the current counter value

We also need to update the tests. Edit the CountResourceTest class to match:

package org.acme.spring.scheduler;
import static io.restassured.RestAssured.given;
import static org.hamcrest.CoreMatchers.containsString;
import org.junit.jupiter.api.Test;
import io.quarkus.test.junit.QuarkusTest;
@QuarkusTest
public class CountResourceTest {
    @Test
    public void testHelloEndpoint() {
        given()
                .when().get("/count")
                .then()
                .statusCode(200)
                .body(containsString("count"));  (1)
    }
}

Ensure that the response contains count

Package and run the application

Run the application with: ./mvnw compile quarkus:dev. In another terminal, run curl localhost:8080/count to check the counter value. After a few seconds, re-run curl localhost:8080/count to verify the counter has been incremented.

Observe the console to verify that the following messages has been displayed: - Cron expression hardcoded - Cron expression configured in application.properties - Fixed Rate expression - Fixed Rate expression configured in application.properties These messages indicate that the executions of methods annotated with @Scheduled have been triggered.

As usual, the application can be packaged using ./mvnw clean package and executed using the -runner.jar file. You can also generate the native executable with ./mvnw clean package -Pnative.

Using Property Expressions

Quarkus supports the use of property expressions in the application.properties file so to externalize the configuration of the tasks you should store the properties in the application.properties file and use the fixedRateString, initialDelayString params respectively.

Note that this configuration is a build time configuration, the property expression will be resolved at build time.

Unsupported Spring Scheduled functionalities

Quarkus currently only supports a subset of the functionalities that Spring @Scheduled provides with more features being planned. Currently, the fixedDelay and fixedDelayString parameters are not supported, in other words, @Scheduled methods are always executed independently.

Important Technical Note

Please note that the Spring support in Quarkus does not start a Spring Application Context nor are any Spring infrastructure classes run. Spring classes and annotations are only used for reading metadata and / or are used as user code method return types or parameter types. What that means for end users, is that adding arbitrary Spring libraries will not have any effect. Moreover Spring infrastructure classes (like org.springframework.beans.factory.config.BeanPostProcessor for example) will not be executed.