I wonder if anyone can advise: I have a scenario where a scheduled job being run by Quartz will update an arraylist of objects every hour.
But I need this arraylist of objects to be visible to all sessions created by Tomcat. So what I'm thinking is that I write this object somewhere every hour from the Quartz job that runs so that each session can access it.
Can anyone say how best this may be achieved? I was wondering about the object being written to servlet context from the Quartz job? The alternative is having each session populate the arraylist of objects from a database table.
Thanks
Mr Morgan.
Yes, I would store the list in the ServletContext
as an application-scoped attribute. Pulling the data from a database instead is probably less efficient, since you're only updating the list every hour. Creating a ServletContextListener
might be necessary in order to give the Quartz task a reference to the ServletContext
object. The ServletContext
can only be retrieved from JavaEE-related classes like Servlets and Listeners.
EDIT: In the ServletContextListener, when you create the job, you can pass the list into the job by adding it to a JobDataMap.
public class MyServletContextListener implements ServletContextListener{
public void contextInitialized(ServletContextEvent event){
ArrayList list = new ArrayList();
//add to ServletContext
event.getServletContext().setAttribute("list", list);
JobDataMap map = new JobDataMap();
map.put("list", list);
JobDetail job = new JobDetail(..., MyJob.class);
job.setJobDataMap(map);
//execute job
}
public void contextDestroyed(ServletContextEvent event){}
}
//Quartz job
public class MyJob implements Job{
public void execute(JobExecutionContext context){
ArrayList list = (ArrayList)context.getMergedJobDataMap().get("list");
//...
}
}