Thread Scheduler

[Nilesh Raje]

Hi there,

I have a task here and needed some inputs from you guys.
This task needs to be done using jdk1.4 only in weblogic 9 server

I have written a small thread which runs as a start up class once i a start my weblogic server.

Example:

I am making this thread poll the database every 5 min to check is there are any invalid recrods and if they are found This thread deletes it and sends email to user.
This works fine.

Now I have to also add one more new task to this in the same class.
I have to also send emails every midnight about the records in the database.

Here is where i am facing problem.

suppose i start my weblogic server at 5.00 pm then my program needs to calculate the midnight time and trigger exactly at midnight and there after run every midnight. simultaneously the polling mechanism i wrote should run as i have implemented every 5 min.

How can i achieve this in the same class? Do I need to start a seprate thread?
I came across a article which says timer task and timer in jdk1.4 should not be used in a managed environment like weblogic container as it runs a thread which is out of the scope of weblogic.

How do i go about this?

[Steve Luke]

Nilesh Raje wrote:I came across a article which says timer task and timer in jdk1.4 should not be used in a managed environment like weblogic container as it runs a thread which is out of the scope of weblogic.

Any thread YOU create, if it is a Timer/TimerTask or Thread t = new Thread() is not managed by the web container. Some people (me included) don't like to do this. The JVM for the application container should be used for the web application(s) only and are best managed by app server. That is my opinion, anyway.


So I usually suggest to have your web container trigger an external application to start/stop at the correct times. For example, you polling/record management application doesn't really have much to do with the web app, so why put it in weblogic at all. Have a standalone service which polls the DB every 5 minutes and, at midnight sends an email. Weblogic would start the service when weblogic itself starts up and end the polling service when weblogic shuts down. In this case you could either use Timer/TimerTask or your OS' scheduling software to run the polling job.

If, on the other hand, you really want to run the task inside weblogic, then you are going to have to make a Thread, and this Thread will be outside weblogic's management in any case, so using a Timer/TimerTask is no different than your current solution in that regards. Timer/TimerTask does give you a lot more benefit in how the scheduled task occurs, so I would suggest the Timer/TimerTask solution.

[Henry Wong]

If, on the other hand, you really want to run the task inside weblogic, then you are going to have to make a Thread, and this Thread will be outside weblogic's management in any case, so using a Timer/TimerTask is no different than your current solution in that regards. Timer/TimerTask does give you a lot more benefit in how the scheduled task occurs, so I would suggest the Timer/TimerTask solution.

To be fair, this is actually common -- sometimes, it is just not possible to avoid starting another thread.

BTW, you also never mentioned what is the application type -- servlet? EJB? MBean? Web Service? Some of those types have start and stop methods (callbacks), that can be used to help manage the threads.

Henry

[Henry Wong]

This task needs to be done using jdk1.4 only in weblogic 9 server

BTW, I don't think that this is a valid configuration, as I believe that Weblogic 9 requires Java 5.

Henry

[Nilesh Raje]

Well the configuration is valid and set up as per requirement.

Weblogic uses jdk1.5 but my application needs to use compile time JDK1.4 and runtime JRE1.5 as in this thread I am taking a handle to a EJB which is again compiled in jdk1.4 and run in jdk1.5 runtime.

Anyways I dont have any issues with configurtion cause thats how it has to be.

I could have scheduled this using unix cron but the requirement is to startup up with the server only. This has to start up with weblogic.

Well coming back to the question i raised. I have used Quartz for this.I found this pretty handy.
For more info here is the url http://www.opensymphony.com/
Timer and Timer task are not good options as they have a overhead and performance hit. I found several articles for this.

Here is what i have come up with now.

I have 2 classes which do 2 different tasks And the scheduled them in one class.


This class is for task 1.

 

import java.util.Date;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.quartz.Job;
import org.quartz.JobExecutionContext;
import org.quartz.JobExecutionException;


public class SimpleJob implements Job {

    private static Log _log = LogFactory.getLog(SimpleJob.class);

    /**
     * Quartz requires a public empty constructor so that the
     * scheduler can instantiate the class whenever it needs.
     */
    public SimpleJob() {
    }

    /**
     * <p>
     * Called by the <code>{@link org.quartz.Scheduler}</code> when a
     * <code>{@link org.quartz.Trigger}</code> fires that is associated with
     * the <code>Job</code>.
     * </p>
     * 
     * @throws JobExecutionException
     *             if there is an exception while executing the job.
     */
    public void execute(JobExecutionContext context)
        throws JobExecutionException {

        // This job simply prints out its job name and the
        // date and time that it is running
        String jobName = context.getJobDetail().getFullName();
        _log.info("SimpleJob says: " + jobName + " executing at " + new Date());
        
        System.out.println("Simple Job Class.!");
    }

}

This class is for task 2.

 
import java.util.Date;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.quartz.Job;
import org.quartz.JobExecutionContext;
import org.quartz.JobExecutionException;


public class HelloJob implements Job {

	 private static Log _log = LogFactory.getLog(SimpleJob.class);

	    /**
	     * Quartz requires a public empty constructor so that the
	     * scheduler can instantiate the class whenever it needs.
	     */
	    public HelloJob() {
	    }

	    /**
	     * <p>
	     * Called by the <code>{@link org.quartz.Scheduler}</code> when a
	     * <code>{@link org.quartz.Trigger}</code> fires that is associated with
	     * the <code>Job</code>.
	     * </p>
	     * 
	     * @throws JobExecutionException
	     *             if there is an exception while executing the job.
	     */
	    public void execute(JobExecutionContext context)
	        throws JobExecutionException {

	        // This job simply prints out its job name and the
	        // date and time that it is running
	        String jobName = context.getJobDetail().getFullName();
	        _log.info("Hello Job says: " + jobName + " executing at " + new Date());
	        
	        System.out.println("Hello Job Class.!");
	    }

}

This is my main scheduler.

 

import java.util.Date;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.quartz.CronTrigger;
import org.quartz.JobDetail;
import org.quartz.Scheduler;
import org.quartz.SchedulerFactory;
import org.quartz.SchedulerMetaData;
import org.quartz.impl.StdSchedulerFactory;


public class CronTriggerExample {

    public void run() throws Exception {
        Log log = LogFactory.getLog(CronTriggerExample.class);

        log.info("------- Initializing -------------------");

        // First we must get a reference to a scheduler
        SchedulerFactory sf = new StdSchedulerFactory();
        Scheduler sched = sf.getScheduler();

      

        // job 1 will run every 20 seconds
        JobDetail job = new JobDetail("job1", "group1", SimpleJob.class);
        CronTrigger trigger = new CronTrigger("trigger1", "group1", "job1","group1", "0/20 * * * * ?");
        sched.addJob(job, true);
        Date ft = sched.scheduleJob(trigger);
        log.info(job.getFullName() + " has been scheduled to run at: " + ft
                + " and repeat based on expression: "
                + trigger.getCronExpression());
        
        

        // job 2 will run every day at 12.00am
        JobDetail helloJob  = new JobDetail("job2", "group1", HelloJob.class);
        trigger = new CronTrigger("trigger2", "group1", "job2", "group1","0 0 12am * * ?");
        sched.addJob(helloJob, true);
        
        ft = sched.scheduleJob(trigger);
        
        log.info(job.getFullName() + " has been scheduled to run at: " + ft
                + " and repeat based on expression: "
                + trigger.getCronExpression());

        log.info(helloJob.getFullName() + " has been scheduled to run at: " + ft
                + " and repeat based on expression: "
                + trigger.getCronExpression());
       
        log.info("------- Starting Scheduler ----------------");

        // All of the jobs have been added to the scheduler, but none of the
        // jobs
        // will run until the scheduler has been started
        sched.start();

        log.info("------- Started Scheduler -----------------");


    }

    public static void main(String[] args) throws Exception {

        CronTriggerExample example = new CronTriggerExample();
        example.run();
    }

}