I have tasks to do as soon as I upload my application, they are executed repeatedly like this:
@Scheduled(fixedRate = 10000)
public void scheduleFixedRateTask() {
System.out.println("Fixed rate task - " + System.currentTimeMillis()/10000);
}
But sometimes I need to update the time interval and I did not want to have to stop the application every time to do this. So I was wondering if there is a way to extend Spring's @Scheduled so that it reads some configuration file, how?
You can parameterize the Spring annotation, the parameter is a bit different:
//fixedDelay task:
@Scheduled(fixedDelayString = "${fixedDelay.in.milliseconds}")
//fixedRate task:
@Scheduled(fixedRateString = "${fixedRate.in.milliseconds}")
//A cron expression based task:
@Scheduled(cron = "${cron.expression}")
Just add the property to your configuration file.
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Updating Spring properties with the running application is often a non-trivial problem. This way it is often easier to implement this type of scheduling programmatically:
@Autowired private TaskScheduler scheduler;
private ScheduledFuture scheduledTask;
@PostConstruct
public void init() throws Exception {
// Dispara com valor padrao, alternativamente
// isso pode ser lido do arquivo de propriedades
scheduleFixedRateTask(10000L);
}
public void scheduleFixedRateTask(final long rate) {
if (scheduledTask!= null) {
// Em um código real você provavelmente quer fazer algo mais robusto
// do que interromper a tarefa logo de cara.
scheduledTask.cancel(true);
}
Runnable task = new Runnable() {
public void run() {
System.out.println("Fixed rate task - " + System.currentTimeMillis()/rate);
}
};
scheduledTask= scheduler.scheduleWithFixedDelay(task, rate);
}
For more complex use cases Spring has support for Quartz , but Quartz is a cannon if your application has no real need for jobs persistent / transactional / distributed.
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