JAVA EE: How to schedule jobs using @Scheduled annotation (Fixed Rate) in spring?

Saturday, 8 December 2018

How to schedule jobs using @Scheduled annotation (Fixed Rate) in spring? | Spring Scheduler tutorial

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Introduction to Fixed Rate Scheduling

Automating background processes is an essential part of enterprise Java development. In the Spring Framework, running periodic background jobs is straightforward with the @Scheduled annotation.

In this tutorial, you will explore how to run tasks at a fixed rate, meaning executions are triggered at regular intervals measured from the start time of each execution.

How Does fixedRate Work?

When you define @Scheduled(fixedRate = 5000), Spring attempts to run the annotated method every 5 seconds, counting from the initiation time of each task.

Predictable Cadence: Ensures invocations kick off at regular clock increments.
Independent Execution: Ideal for independent tasks like polling status, streaming metrics, or cache invalidation where each cycle does not rely on the outcome of the last.

Key Setup Annotations

@EnableScheduling: Placed on your configuration or main class to activate Spring’s background scheduling capability.
@Component: Designates the service or worker class as a Spring-managed bean.
@Scheduled(fixedRate = ...): Placed on a void method that takes no arguments to declare its recurring execution frequency.

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How to schedule jobs using @Scheduled annotation (Fixed Rate) in spring? | Spring Scheduler tutorial

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0"

    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <groupId>com.ram.core</groupId>

    <artifactId>SpringDemo</artifactId>

    <packaging>jar</packaging>

    <version>1.0-SNAPSHOT</version>

    <name>SpringDemo</name>

    <url>http://maven.apache.org</url>

    <properties>

        <spring.version>5.0.9.RELEASE</spring.version>

    </properties>

    <dependencies>

        <dependency>

            <groupId>junit</groupId>

            <artifactId>junit</artifactId>

            <version>3.8.1</version>

            <scope>test</scope>

        </dependency>

        <!-- Spring 5 dependencies -->

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-core</artifactId>

            <version>${spring.version}</version>

        </dependency>

        <!-- https://mvnrepository.com/artifact/org.springframework/spring-context-support -->

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-context-support</artifactId>

            <version>${spring.version}</version>

        </dependency>

    </dependencies>

</project>

ScheduledTasks.java

package com.ram.scheduler;

import java.text.SimpleDateFormat;

import java.util.Date;

import org.springframework.scheduling.annotation.EnableScheduling;

import org.springframework.scheduling.annotation.Scheduled;

import org.springframework.stereotype.Component;

@Component

@EnableScheduling

public class ScheduledTasks

{

    private static final SimpleDateFormat dateFormat = new SimpleDateFormat(

            "HH:mm:ss");

    @Scheduled(fixedRate = 5000)

    public void reportCurrentTime()

    {

        System.out.println(

                "Current time = " + dateFormat.format(new Date()));

    }

}

Spring-Scheduler.xml

<beans xmlns="http://www.springframework.org/schema/beans"

    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 

    xmlns:context="http://www.springframework.org/schema/context"

    xsi:schemaLocation="http://www.springframework.org/schema/beans

    http://www.springframework.org/schema/beans/spring-beans-4.3.xsd

    http://www.springframework.org/schema/context

    http://www.springframework.org/schema/context/spring-context-4.3.xsd">

    <context:component-scan base-package="com.ram" />

</beans>

App.java

package com.ram.core;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class App

{

    public static void main(String[] args)

    {

        ApplicationContext context = new ClassPathXmlApplicationContext(

                "Spring-Scheduler.xml");

    }

}

Output

Nov 16, 2018 10:17:33 AM org.springframework.context.support.AbstractApplicationContext prepareRefresh

INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@4783da3f: startup date [Fri Nov 16 10:17:33 IST 2018]; root of context hierarchy

Nov 16, 2018 10:17:33 AM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions

INFO: Loading XML bean definitions from class path resource [Spring-Scheduler.xml]

Nov 16, 2018 10:17:34 AM org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor finishRegistration

INFO: No TaskScheduler/ScheduledExecutorService bean found for scheduled processing

Current time = 10:17:34

Current time = 10:17:39

Current time = 10:17:44

Current time = 10:17:49

Current time = 10:17:54

Current time = 10:17:59