Question

I want to do the following:

Normally you implement Play-Jobs by implementing a Class which extends the http://www.playframework.org/documentation/api/1.2.4/play/jobs/Job.html which is added to the pool OnApplicationStart…

I want to add Cron-Jobs now at Runtime (add Tasks via GUI…) but im not sure how to implement that.

I looked into the JobsPlugin and found the following lines:

job.nextPlannedExecution = nextDate;
executor.schedule((Callable<V>)job, nextDate.getTime() - now.getTime(), TimeUnit.MILLISECONDS);
job.executor = executor;

Do i have to add them like that?

Is that even possible? Cause i cant find any line, where the Job itself is told, which Cron-Expression it should follow…

String cron = job.getClass().getAnnotation(On.class).value();

Is this line called from outside again after a Job-Excecution and a new job.nextPlannedExecution is set?

---

Ok i hope im not answering my own question now, but could this be the solution?:

I implement my own Job-Class, add a Attribute e.g. cronExpression and overrride the Job’s

public void _finally() {
    super._finally();
    if (executor == JobsPlugin.executor) {
        JobsPlugin.scheduleForCRON(this);
    }
}

to implement my own sheduleForCron()

Answer 1

Looking at the source code for JobsPlugin, you should just be able to mimic what is done using the scheduledJobs and executor attributes.

If you take a look at the onApplicationStart method, this shows how Jobs annotated with @On or ‘@Everyare managed in the job pool.Onuses the CRON expression and usesscheduleForCRON, where asEvery` uses the executor to manage the repetition.

As the scheduledJobs and executor attributes are public static, you can access and maniplulate this as much as you wish, so I would suggest reading through the source code of JobsPlugin, especially the following code, and to mimic it in your own codebase.

        // @On
        if (clazz.isAnnotationPresent(On.class)) {
            try {
                Job<?> job = ((Job<?>) clazz.newInstance());
                scheduledJobs.add(job);
                scheduleForCRON(job);
            } catch (InstantiationException ex) {
                throw new UnexpectedException("Cannot instanciate Job " + clazz.getName());
            } catch (IllegalAccessException ex) {
                throw new UnexpectedException("Cannot instanciate Job " + clazz.getName());
            }
        }
        // @Every
        if (clazz.isAnnotationPresent(Every.class)) {
            try {
                Job job = (Job) clazz.newInstance();
                scheduledJobs.add(job);
                String value = job.getClass().getAnnotation(Every.class).value();
                if (value.startsWith("cron.")) {
                    value = Play.configuration.getProperty(value);
                }
                value = Expression.evaluate(value, value).toString();
                if(!"never".equalsIgnoreCase(value)){
                    executor.scheduleWithFixedDelay(job, Time.parseDuration(value), Time.parseDuration(value), TimeUnit.SECONDS);
                }
            } catch (InstantiationException ex) {
                throw new UnexpectedException("Cannot instanciate Job " + clazz.getName());
            } catch (IllegalAccessException ex) {
                throw new UnexpectedException("Cannot instanciate Job " + clazz.getName());
            }
        }