Chapter 31. Scheduling and Thread Pooling

JobDetail objects contain all information needed to run a job. The Spring Framework provides a JobDetailObject that makes the JobDetail easier to configure and with sensible defaults. Let's have a look at an example:

<object name="ExampleJob" type="Spring.Scheduling.Quartz.JobDetailObject, Spring.Scheduling.Quartz">
  <property name="JobType" value="Example.Quartz.ExampleJob, Example.Quartz" />
  <property name="JobDataAsMap">
    <dictionary>
      <entry key="Timeout" value="5" />
    </dictionary>
  </property>
</object>

The job detail object has all information it needs to run the job (ExampleJob). The timeout is specified in the job data dictionary. The job data dictonary is available through the JobExecutionContext (passed to you at execution time), but the JobDetailObject 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 JobDetailObject will automatically apply it:

namespace Example.Quartz;

public class ExampleJob extends QuartzJobObject {

  private int timeout;
  
  /// <summary>
  /// Setter called after the ExampleJob is instantiated
  /// with the value from the JobDetailObject (5)
  /// </summary>
  public int Timeout {
     set { timeout = value; };
  }
  
  protected override void ExecuteInternal(JobExecutionContext context) {
      // do the actual work
  }
}

All additional settings from the job detail object 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 object name of the job detail object (in the example above, this is ExampleJob).

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

<object id="JobDetail" type="Spring.Scheduling.Quartz.MethodInvokingJobDetailFactoryObject, Spring.Scheduling.Quartz">
  <property name="TargetObject" ref="ExampleBusinessObject" />
  <property name="TargetMethod" value="DoIt" />
</object>

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
  }
}

<object id="ExampleBusinessObject" type="Examples.BusinessObjects.ExampleBusinessObject, Examples.BusinessObjects"/>

Using the MethodInvokingJobDetailFactoryObject, 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 MethodInvokingJobDetailFactoryObject non-concurrent, set the concurrent flag to false.

<object id="JobDetail" type="Spring.Scheduling.Quartz.MethodInvokingJobDetailFactoryObject, Spring.Scheduling.Quartz">
  <property name="TargetObject" ref="ExampleBusinessObject" />
  <property name="TargetMethod" value="DoIt" />
  <property name="Concurrent" value="false" />
</object>

	Note
	By default, jobs will run in a concurrent fashion. Also note that when using MethodInvokingJobDetailFactoryObject you can't use database persistence for Jobs. See the class documentation for additional details.

We've created job details and jobs. We've also reviewed the convenience class 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 SchedulerFactoryObject. Several triggers are available within Quartz. Spring offers two subclassed triggers with convenient defaults: CronTriggerObject and SimpleTriggerObject

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

Find below a couple of examples:

<object id="SimpleTrigger" type="Spring.Scheduling.Quartz.SimpleTriggerObject, Spring.Scheduling.Quartz">
  <!-- see the example of method invoking job above -->
  <property name="JobDetail" ref="ExampleJob" />
  
  <!-- 10 seconds -->
  <property name="StartDelay" value="10s" />
 
  <!-- repeat every 50 seconds -->
  <property name="RepeatInterval" value="50s" />
</object>

<object id="CronTrigger" type="Spring.Scheduling.Quartz.CronTriggerObject, Spring.Scheduling.Quartz">
    <property name="JobDetail" ref="ExampleJob" />

    <!-- run every morning at 6 AM -->
    <property name="CronExpressionString" value="0 0 6 * * ?" />
</object>

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 SchedulerFactoryObject:

<object id="quartzSchedulerFactory" type="Spring.Scheduling.Quartz.SchedulerFactoryObject, Spring.Scheduling.Quartz">
    <property name="triggers">
        <list>
            <ref object="CronTrigger" />
            <ref object="SimpleTrigger" />
        </list>
    </property>
</object>

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