QuartzJob.java

package com.blogspot.alotacode.scheduler;

import java.util.List;

import org.apache.log4j.Logger;
import org.quartz.JobExecutionContext;
import org.quartz.JobExecutionException;
import org.quartz.SchedulerException;
import org.springframework.scheduling.quartz.QuartzJobBean;

/**
 * @author Timothy Mugayi
 */
public abstract class QuartzJob<T> extends QuartzJobBean  {

    private static final Logger log = Logger.getLogger(QuartzJob.class);
		  
    @SuppressWarnings("unchecked")
    @Override
    protected void executeInternal(JobExecutionContext context) throws JobExecutionException {
        try {      
            List<JobExecutionContext> jobs = context.getScheduler().getCurrentlyExecutingJobs();
            if (jobs != null && !jobs.isEmpty()) {
            	  for (JobExecutionContext job : jobs) {
      	            if (job.getTrigger().equals(context.getTrigger()) && !job.getJobInstance().equals(this)) {
      	            	log.info("There's another instance running, : " + this);
      	                return;
      	            }
      	        }
            }
        } catch (SchedulerException e) {
           log.error(e.getCause());
        }
    }
}