Don't use a servlet to store the data. Rather store the data as an attribute of the ServletContext. You can do it with help of a ServletContextListener. The very same listener class can also be used to reload the data at timed intervals with help of ScheduledExecutorService.
Here's a kickoff example:
public class Config implements ServletContextListener {
private ScheduledExecutorService scheduler;
@Override
public void contextInitialized(ServletContextEvent event) {
Data data = new Data();
event.getServletContext().setAttribute("data", data);
scheduler = Executors.newSingleThreadScheduledExecutor();
scheduler.scheduleAtFixedRate(new Reloader(data), 0, 30, TimeUnit.DAYS);
}
@Override
public void contextDestroyed(ServletContextEvent event) {
scheduler.shutdownNow();
}
}
(note that there's no TimeUnit.MONTH, so this is the best you can get for "once a month")
Where the Reloader class look like this:
public class Reloader implements Runnable {
private Data data;
public Reloader(Data data) {
this.data = data;
}
@Override
public void run() {
data.reload();
}
}
After registering the listener in /WEB-INF/web.xml as follows
<listener>
<listener-class>com.example.Config</listener-class>
</listener>
it will create the Data instance and a single thread scheduler which executes the data.reload() every 30 days and you can access the Data instance in every servlet as follows:
Data data = (Data) getServletContext().getAttribute("data");
and in JSPs as follows:
${data}
