I need to do a periodic operation (call a java method) in my web app (jsp on tomcat). How can i do this ? Java daemon or others solutions ?
You could use a ScheduledExecutorService
for periodic execution of a task. However, if you require more complex cron-like scheduling then take a look at Quartz. In particular I'd recommend using Quartz in conjunction with Spring if you go down this route, as it provides a nicer API and allows you to control your job firing in configuration.
ScheduledExecutorService Example (taken from Javadoc)
import static java.util.concurrent.TimeUnit.*;
class BeeperControl {
private final ScheduledExecutorService scheduler =
Executors.newScheduledThreadPool(1);
public void beepForAnHour() {
final Runnable beeper = new Runnable() {
public void run() { System.out.println("beep"); }
};
final ScheduledFuture<?> beeperHandle =
scheduler.scheduleAtFixedRate(beeper, 10, 10, SECONDS);
scheduler.schedule(new Runnable() {
public void run() { beeperHandle.cancel(true); }
}, 60 * 60, SECONDS);
}
}
Adams answer is right on the money. If you do end up rolling your own (rather than going the quartz route), you'll want to kick things off in a ServletContextListener. Here's an example, using java.util.Timer, which is more or less a dumb version of the ScheduledExexutorPool.
public class TimerTaskServletContextListener implements ServletContextListener
{
private Timer timer;
public void contextDestroyed( ServletContextEvent sce )
{
if (timer != null) {
timer.cancel();
}
}
public void contextInitialized( ServletContextEvent sce )
{
Timer timer = new Timer();
TimerTask myTask = new TimerTask() {
@Override
public void run()
{
System.out.println("I'm doing awesome stuff right now.");
}
};
long delay = 0;
long period = 10 * 1000; // 10 seconds;
timer.schedule( myTask, delay, period );
}
}
And then this goes in your web.xml
<listener>
<listener-class>com.TimerTaskServletContextListener</listener-class>
</listener>
Just more food for thought!
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