Question

I have a following problem with Quartz JobDataMap. I expect that when using simple Quartz Job and passing not-primitive object (e.g. instance of StringBuilder) into JobDateMap, method execute (from my job) should be always invoked with different copy of objected I put. Unfortunately I always get instance of object I put into JobDateMap (like it would be a StatefulJob).

In bellow example I expect to get single ‘*’ in every invocation while I get one more ‘*’ every time.

public class MyJob implements Job {

    public static void main(String[] args) throws SchedulerException {

        SchedulerFactory schedFact = new StdSchedulerFactory();
        Scheduler sched = schedFact.getScheduler();

        JobDetail jobDetail = new JobDetail("job", Scheduler.DEFAULT_GROUP, MyJob.class);
        jobDetail.getJobDataMap().put("param", new StringBuilder());

        Trigger trigger = TriggerUtils.makeImmediateTrigger("trigger", 10, 100);
        trigger.setGroup(Scheduler.DEFAULT_GROUP);

        sched.scheduleJob(jobDetail, trigger);
        sched.start();

        try {
            Thread.sleep(1000L);
        } catch (Exception e) {}

        sched.shutdown(true);

    }

    @Override
    public void execute(JobExecutionContext context) throws JobExecutionException {
        StringBuilder sb = (StringBuilder) context.getMergedJobDataMap().get("param");
        sb.append("*");
        System.out.println(sb.toString());

    }
}

I think, I’m missing something about how Quartz is working. Anybody knows what?

Answer 1

"Only store primitive data types (including Strings) in JobDataMap to
avoid data serialization issues short and long-term."

source: http://www.quartz-scheduler.org/documentation/2.3.1-SNAPSHOT/best-practices.html#jobdatamap-tips