Question

I’m looking into scheduling my application with Quartz, but in all cases, the job trigger seems to be a one-time activity, and changes to the trigger need the application to be re-deployed to take effect.
Is there any way I can have the job trigger check for changes to the job schedule without having to redeploy the code?
Thanks,

Answer 1

1. Trap some user-driven event, like updating a text value, for example a cron-string to schedule a job
2. Locate and unschedule/delete the old job and trigger.

3. Schedule the job again, using the new trigger.

   public static <T> T scheduleCronJob(Class<T> clazz, String cronString, String uid){
       try{            
           if(cronString == null){
               throw new CronStringConfigurationException();
           }
   
           String jobGroupName = "cronJobsGroup";
           String jobName = "cronJob" + uid;
           String triggerGroupName = "cronTriggers";
           String triggerName = "triggerFor" + uid;
   
           JobDetail jobDetail = new JobDetail(jobName, jobGroupName, clazz);
   
           CronTrigger trigger = new CronTrigger(
                   triggerName, triggerGroupName, 
                   jobName, jobGroupName, 
                   cronString);
   
           JobDataMap jobDataMap = new JobDataMap();
           jobDetail.setJobDataMap(jobDataMap);
   
           getScheduler().scheduleJob(jobDetail, trigger);
       } catch(Exception e){
       // print error message, throw stack trace
       }
       return null;
   }
   
   public static void reloadCronJob(Class clazz, String cronString, String uid) throws SystemException, ParseException, SchedulerException, 
       CronStringConfigurationException, PortalException{
       // locate the job 
       String jobGroupName = "cronJobs";
       String jobName = "jobFor" + uid;
   
       if(cronString == null){
           throw new CronStringConfigurationException();
       }
   
       JobDetail jobDetail = null;
       Class<?> jobClass = null;
   
       // remove the old job/trigger if it exists
       try{
           jobDetail = scheduler.getJobDetail(jobName, jobGroupName);
           if(jobDetail != null){
               jobClass = jobDetail.getJobClass();
           }
           scheduler.deleteJob(jobName, jobGroupName);
       } catch(Exception e){
           e.printStackTrace();
       }
   
       if(jobClass == null){
           jobClass = clazz;
       }
   
       // create a new trigger
       scheduleCronJob(jobClass, expandoColumnName, uid);
   
       System.out.println("(re)scheduled job " + jobName + " using new cron string " + cronString);
   }