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.
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.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"); //... } }