Why do we need scheduling?
Scheduling is needed if you want to automate the repetition of a task at specific intervals or particular date. You could of course manually watch the time and execute your task, albeit an inefficient task. Who wants to watch the computer every 3 seconds just to hit the Enter key? No one.
We want to run the following sample class at specific intervals:
The task that we're interested is inside the work() method. This example is based on Mark Fisher's example at Task Scheduling Simplifications in Spring 3.0. This method retrieves the thread name, prints the starting and beginning of the method, simulates work by putting the thread in sleep for 10 seconds.
To schedule this using Quartz, we'll do it in two ways via the JobDetailBean and via the MethodInvokingJobDetailFactoryBean.
The MethodInvokingJobDetailFactoryBean is the simpler of the two, albeit simple options. So we'll start with that.
Using the MethodInvokingJobDetailFactoryBean
Often you just need to invoke a method on a specific object. Using the MethodInvokingJobDetailFactoryBean you can do exactly this.... 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.Let's examine an actual example. We'll create a new class SyncWorker that implements a Worker interface.
This worker is synchronous which means if we have to call this worker 10 times, it will block the other workers. They cannot start immediately until the first one is finished. If you like to see an example of asynchronous scheduling, please see Spring 3 - Task Scheduling via Annotations: @Scheduled, @Async
To run this using the MethodInvokingJobDetailFactoryBean, we need to declare it in an XML configuration:
We have declared our SyncWorker as a simple bean:
Then we made a reference to our worker inside a MethodInvokingJobDetailFactoryBean. On the targetMethod property, we assign the method name work() that needs to be scheduled.
In order for this to be triggered, we need a Trigger.
This trigger runs every 10 seconds, with a starting delay of 10 seconds as well.
In order for this trigger to be managed, we need a Scheduler
The SchedulerFactoryBean purpose is to schedule the actual jobs assigned in the triggers. You may wonder why we need to have a scheduler, a trigger, and a job just to schedule a single task in Quartz?
Quartz uses Trigger, Job and JobDetail objects to realize scheduling of all kinds of jobs. For the basic concepts behind Quartz, have a look at http://www.opensymphony.com/quartz. For convenience purposes, Spring offers a couple of classes that simplify the usage of Quartz within Spring-based applications. Source: http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/html/scheduling.htmlLet's run the application and see the output on the logs:
Notice how our worker is executed. It runs synchronously as expected. The numbers in Worker-1, Worker-2, and etc represents the thread ppol. Our max Worker is 10, so we have a pool size of 10. To modify this value, add the following quartzProperties in the SchedulerFactoryBean:
Let's explore another way of scheduling using Quartz. We'll use the JobDetailBean.
What is a JobDetailBean
Convenience subclass of Quartz's JobDetail class, making bean-style usage easier.Let's examine an actual example. We'll create a custom class CustomJob that extends QuartzJobBean and implements StatefulJob
JobDetail itself is already a JavaBean but lacks sensible defaults. This class uses the Spring bean name as job name, and the Quartz default group ("DEFAULT") as job group if not specified.
Notice our worker is a normal private field. We have assigned a setter method for this worker.
This is required so that Spring can inject the value from the XML configuration. Our worker is executed inside the executeInternal() method:
You can access various details of your job via the JobExecutionContext.
To activate our CustomJob, we need to enable it in the XML configuration.
The configuration is similar with our first example using MethodInvokingJobDetailFactoryBean. The main difference here is we're using aJobDetailBean
We're also using a CronTrigger. Nonetheless, the idea is similar with our initial example.
Let's run our application and see the output:
Same result. We just have more logs because of the CustomJob.
That's it. We've added scheduling support using the Quartz Scheduler. We've used two support beans to realize our goal. Feel free to modify the MVC app to fit your needs. You might wanna try integrating a web service with scheduling and show the results via MVC. The welcome page is accesible at
http://localhost:8080/spring-mvc-quartz-scheduling/krams/main/welcomeThe best way to learn further is to try the actual application.
Download the project
You can access the project site at Google's Project Hosting at http://code.google.com/p/spring-mvc-scheduling/
You can download the project as a Maven build. Look for the spring-mvc-quartz-scheduling.zip in the Download sections.
You can run the project directly using an embedded server via Maven.
For Tomcat: mvn tomcat:run
For Jetty: mvn jetty:run
If you need to know more about Task Scheduling in Spring 3.0, please visit the following links:
- Task Scheduling Simplifications in Spring 3.0
- Spring Framework 3 Reference, Chapter 25. Task Execution and Scheduling
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