Spring 3: Timer Tasks

Using TimeTask is pretty old way, and is not recommended anymore. Use @Scheduled annotation for the latest and recommended approach.

Java Timer is a utility class that schedules tasks for one-time and repeated execution. Through timer tasks, the Spring Framework provides support for executing tasks that are scheduled to be executed periodically for multiple times or even a single time.

There are other ways to achieve scheduler functionality in Java, e.g., running a thread in an infinite loop, using the executor service, or using third-party APIs like Quartz. Timer just happens to be one of them.

Please note that Timer is dependent on system clock so setting back system clock by n hours, would prevent the next execution of timer task also by n hours.

In Spring, there are two ways to use timer tasks:

• Configure MethodInvokingTimerTaskFactoryBean
• Extend java.util.TimerTask

Let’s demo the usage of each one using examples.

1. Configure MethodInvokingTimerTaskFactoryBean

In this method, timer task bean and method to be executed inside it, is configured in org.springframework.scheduling.timer.MethodInvokingTimerTaskFactoryBean definition. This is a factory bean which exposes a TimerTask object which delegates job execution to a specified (static or non-static) method. This avoids the need to implement a one-line TimerTask that just invokes an existing business method.

A sample spring configuration will look like this:

<beans>

    <bean id="demoTimerTask" class="com.howtodoinjava.task.DemoTimerTask"></bean>

    <bean id="timerTaskFactoryBean"
        class="org.springframework.scheduling.timer.MethodInvokingTimerTaskFactoryBean">
    <property name="targetObject" ref="demoTimerTask"></property>
    <property name="targetMethod" value="execute"></property>
  </bean>

    <bean id="scheduledTimerTask" class="org.springframework.scheduling.timer.ScheduledTimerTask">
    <property name="timerTask" ref="timerTaskFactoryBean"></property>
    <property name="period" value="5000"></property>
  </bean>

    <bean class="org.springframework.scheduling.timer.TimerFactoryBean">
    <property name="scheduledTimerTasks">
      <list>
        <ref local="scheduledTimerTask"></ref>
      </list>
    </property>
  </bean>
</beans>

Above timer task will get executed in every 5 seconds. Lets write out demo timer task and test it.

import java.util.Date;

/**
 * No need to implement any interface
 * */
public class DemoTimerTask {

	//Define the method to be called as configured
	public void execute()
	{
		System.out.println("Executed task on ::" + new Date());
	}
}

Now, let us test the timer task.

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class TestDemoTimerTask {
	public static void main(String[] args) {
		new ClassPathXmlApplicationContext("application-config.xml");
	}
}

Executed task on :: Mon Apr 22 09:53:39 IST 2017
Executed task on :: Mon Apr 22 09:53:44 IST 2017

2. Extend java.util.TimerTask

This way, we define our timer task by extending java.util.TimerTask and passing it to the spring configuration to execute it repeatedly.

Lets see how to do it:

<beans>

  <bean id="demoTimerTask" class="com.howtodoinjava.task.DemoTimerTask2"></bean>

  <bean id="scheduledTimerTask" class="org.springframework.scheduling.timer.ScheduledTimerTask">
    <!-- run every 3 secs -->
    <property name="period" value="3000"></property>
    <property name="timerTask" ref="demoTimerTask"></property>
  </bean>

  <bean class="org.springframework.scheduling.timer.TimerFactoryBean">
    <property name="scheduledTimerTasks">
        <list>
            <ref local="scheduledTimerTask"></ref>
        </list>
    </property>
  </bean>

</beans>

The above task will be executed every 3 seconds. Let’s extend our timer task from the TimerTask provided by Java.

import java.util.Date;
import java.util.TimerTask;

public class DemoTimerTask2 extends TimerTask
{
	public void run()
	{
		System.out.println("DemoTimerTask2 running at: " + new Date(this.scheduledExecutionTime()));
	}
}

Let’s test the configuration:

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class TestDemoTimerTask2
{
	public static void main(String[] args)
	{
		new ClassPathXmlApplicationContext("application-config2.xml");
	}
}

DemoTimerTask2 running at: Mon Apr 22 10:01:33 IST 2013
DemoTimerTask2 running at: Mon Apr 22 10:01:36 IST 2013
DemoTimerTask2 running at: Mon Apr 22 10:01:39 IST 2013

Happy Learning !!