JobDetail objects contain all information needed to run a job. Spring provides a so-called JobDetailBean that makes the JobDetail more of an actual JavaBean with sensible defaults. Let's have a look at an example:

<bean name="exampleJob" class="org.springframework.scheduling.quartz.JobDetailBean">
  <property name="jobClass" value="example.ExampleJob" />
  <property name="jobDataAsMap">
    <map>
      <entry key="timeout" value="5" />
    </map>
  </property>
</bean>

The job detail bean has all information it needs to run the job (ExampleJob). The timeout is specified in the job data map. The job data map is available through the JobExecutionContext (passed to you at execution time), but the JobDetailBean also maps the properties from the job data map to properties of the actual job. So in this case, if the ExampleJob contains a property named timeout, the JobDetailBean will automatically apply it:

package example;

public class ExampleJob extends QuartzJobBean {

  private int timeout;
  
  /**
   * Setter called after the ExampleJob is instantiated
   * with the value from the JobDetailBean (5)
   */ 
  public void setTimeout(int timeout) {
    this.timeout = timeout;
  }
  
  protected void executeInternal(JobExecutionContext ctx) throws JobExecutionException {
      // do the actual work
  }
}

All additional settings from the job detail bean are of course available to you as well.

Note: Using the name and group properties, you can modify the name and the group of the job, respectively. By default, the name of the job matches the bean name of the job detail bean (in the example above, this is exampleJob).

Often you just need to invoke a method on a specific object. Using the MethodInvokingJobDetailFactoryBean you can do exactly this:

<bean id="jobDetail" class="org.springframework.scheduling.quartz.MethodInvokingJobDetailFactoryBean">
  <property name="targetObject" ref="exampleBusinessObject" />
  <property name="targetMethod" value="doIt" />
</bean>

The above example will result in the doIt method being called on the exampleBusinessObject method (see below):

public class ExampleBusinessObject {
  
  // properties and collaborators
  
  public void doIt() {
    // do the actual work
  }
}

<bean id="exampleBusinessObject" class="examples.ExampleBusinessObject"/>

Using the MethodInvokingJobDetailFactoryBean, you don't need to create one-line jobs that just invoke a method, and you only need to create the actual business object and wire up the detail object.

By default, Quartz Jobs are stateless, resulting in the possibility of jobs interfering with each other. If you specify two triggers for the same JobDetail, it might be possible that before the first job has finished, the second one will start. If JobDetail classes implement the Stateful interface, this won't happen. The second job will not start before the first one has finished. To make jobs resulting from the MethodInvokingJobDetailFactoryBean non-concurrent, set the concurrent flag to false.

<bean id="jobDetail" class="org.springframework.scheduling.quartz.MethodInvokingJobDetailFactoryBean">
  <property name="targetObject" ref="exampleBusinessObject" />
  <property name="targetMethod" value="doIt" />
  <property name="concurrent" value="false" />
</bean>

	Note
	By default, jobs will run in a concurrent fashion.

We've created job details and jobs. We've also reviewed the convenience bean that allows to you invoke a method on a specific object. Of course, we still need to schedule the jobs themselves. This is done using triggers and a SchedulerFactoryBean. Several triggers are available within Quartz. Spring offers two subclassed triggers with convenient defaults: CronTriggerBean and SimpleTriggerBean.

Triggers need to be scheduled. Spring offers a SchedulerFactoryBean that exposes triggers to be set as properties. SchedulerFactoryBean schedules the actual jobs with those triggers.

A couple of examples:

<bean id="simpleTrigger" class="org.springframework.scheduling.quartz.SimpleTriggerBean">
    <!-- see the example of method invoking job above -->
    <property name="jobDetail" ref="jobDetail" />
    <!-- 10 seconds -->
    <property name="startDelay" value="10000" />
    <!-- repeat every 50 seconds -->
    <property name="repeatInterval" value="50000" />
</bean>

<bean id="cronTrigger" class="org.springframework.scheduling.quartz.CronTriggerBean">
    <property name="jobDetail" ref="exampleJob" />
    <!-- run every morning at 6 AM -->
    <property name="cronExpression" value="0 0 6 * * ?" />
</bean>

OK, now we've set up two triggers, one running every 50 seconds with a starting delay of 10 seconds and one every morning at 6 AM. To finalize everything, we need to set up the SchedulerFactoryBean:

<bean class="org.springframework.scheduling.quartz.SchedulerFactoryBean">
    <property name="triggers">
        <list>
            <ref bean="cronTrigger" />
            <ref bean="simpleTrigger" />
        </list>
    </property>
</bean>

More properties are available for the SchedulerFactoryBean for you to set, such as the calendars used by the job details, properties to customize Quartz with, etc. Have a look at the SchedulerFactoryBean Javadoc for more information.

Using the TimerTask you can create customer timer tasks, similar to Quartz jobs:

public class CheckEmailAddresses extends TimerTask {

  private List emailAddresses;
  
  public void setEmailAddresses(List emailAddresses) {
    this.emailAddresses = emailAddresses;
  }
  
  public void run() {
    // iterate over all email addresses and archive them
  }
}

Wiring it up is simple:

<bean id="checkEmail" class="examples.CheckEmailAddress">
    <property name="emailAddresses">
        <list>
            <value>[email protected]</value>
            <value>[email protected]</value>
            <value>[email protected]</value>
        </list>
    </property>
</bean>

<bean id="scheduledTask" class="org.springframework.scheduling.timer.ScheduledTimerTask">
    <!-- wait 10 seconds before starting repeated execution -->
    <property name="delay" value="10000" />
    <!-- run every 50 seconds -->
    <property name="period" value="50000" />
    <property name="timerTask" ref="checkEmail" />
</bean>

Note that letting the task only run once can be done by changing the period property to 0 (or a negative value).

Similar to the Quartz support, the Timer support also features a component that allows you to periodically invoke a method:

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

The above example will result in the doIt method being called on the exampleBusinessObject (see below):

public class BusinessObject {
  
  // properties and collaborators
  
  public void doIt() {
    // do the actual work
  }
}

Changing the timerTask reference of the ScheduledTimerTask example to the bean doIt will result in the doIt mehtod being executed on a fixed schedule.

The TimerFactoryBean is similar to the Quartz SchedulerFactoryBean in that it serves the same purpose: setting up the actual scheduling. The TimerFactoryBean sets up an actual Timer and schedules the tasks it has references to. You can specify whether or not daemon threads should be used.

<bean id="timerFactory" class="org.springframework.scheduling.timer.TimerFactoryBean">
    <property name="scheduledTimerTasks">
        <list>
            <!-- see the example above -->
            <ref bean="scheduledTask" />
        </list>
    </property>
</bean>

Spring's TaskExecutor interface is identical to the java.util.concurrent.Executor interface. In fact, its primary reason for existence is to abstract away the need for Java 5 when using thread pools. The interface has a single method execute(Runnable task) that accepts a task for execution based on the semantics and configuration of the thread pool.

The TaskExecutor was originally created to give other Spring components an abstraction for thread pooling where needed. Components such as the ApplicationEventMulticaster, JMS's AbstractMessageListenerContainer, and Quartz integration all use the TaskExecutor abstraction to pool threads. However, if your beans need thread pooling behavior, it is possible to use this abstraction for your own needs.

There are a number of pre-built implementations of TaskExecutor included with the Spring distribution. In all likelihood, you shouldn't ever need to implement your own.

Spring's TaskExecutor implementations are used as simple JavaBeans. In the example below, we define a bean that uses the ThreadPoolTaskExecutor to asynchronously print out a set of messages.

import org.springframework.core.task.TaskExecutor;

public class TaskExecutorExample {

  private class MessagePrinterTask implements Runnable {

    private String message;

    public MessagePrinterTask(String message) {
      this.message = message;
    }

    public void run() {
      System.out.println(message);
    }

  }

  private TaskExecutor taskExecutor;

  public TaskExecutorExample(TaskExecutor taskExecutor) {
    this.taskExecutor = taskExecutor;
  }

  public void printMessages() {
    for(int i = 0; i < 25; i++) {
      taskExecutor.execute(new MessagePrinterTask("Message" + i));
    }
  }

}

As you can see, rather than retrieving a thread from the pool and executing yourself, you add your Runnable to the queue and the TaskExecutor uses it's internal rules to decide when the task gets executed.

To configure the rules that the TaskExecutor will use, simple bean properties have been exposed.

<bean id="taskExecutor" class="org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor">
  <property name="corePoolSize" value="5" />
  <property name="maxPoolSize" value="10" />
  <property name="queueCapacity" value="25" />
</bean>

<bean id="taskExecutorExample" class="TaskExecutorExample">
  <constructor-arg ref="taskExecutor" />
</bean>