/actuator/scheduletasks endpoint fails with null pointer exception when there is custom SchedulingConfigurer

[nguyenquoc]

If a custom SchedulingConfigurer is registered with spring boot, then the scheduledtasks actuator will fail with a null pointer exception.

Spring boot 2.1.2

Stack trace:

java.lang.NullPointerException: null
	at java.util.Objects.requireNonNull(Objects.java:203)
	at java.util.Optional.<init>(Optional.java:96)
	at java.util.Optional.of(Optional.java:108)
	at java.util.stream.FindOps$FindSink$OfRef.get(FindOps.java:193)
	at java.util.stream.FindOps$FindSink$OfRef.get(FindOps.java:190)
	at java.util.stream.FindOps$FindOp.evaluateSequential(FindOps.java:152)
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
	at java.util.stream.ReferencePipeline.findFirst(ReferencePipeline.java:464)
	at org.springframework.boot.actuate.scheduling.ScheduledTasksEndpoint$TaskDescription.of(ScheduledTasksEndpoint.java:130)
	at org.springframework.boot.actuate.scheduling.ScheduledTasksEndpoint$TaskDescription.access$900(ScheduledTasksEndpoint.java:108)
	at org.springframework.boot.actuate.scheduling.ScheduledTasksEndpoint.lambda$scheduledTasks$1(ScheduledTasksEndpoint.java:63)

Sample code: https://stackoverflow.com/questions/14630539/scheduling-a-job-with-spring-programmatically-with-fixedrate-set-dynamically/14632758#14632758

The endpoint defined in ScheduledTasksEndpoint.java can only handle CronTrigger's and PeriodicTrigger's. Anything else will cause the endpoint to fail with a null pointer exception

// org.springframework.boot.actuate.scheduling.ScheduleTaskEndpoint.java

        private static ScheduledTasksEndpoint.TaskDescription describeTriggerTask(TriggerTask triggerTask) {
            Trigger trigger = triggerTask.getTrigger();
            if (trigger instanceof CronTrigger) {
                return new ScheduledTasksEndpoint.CronTaskDescription(triggerTask, (CronTrigger)trigger);
            } else if (trigger instanceof PeriodicTrigger) {
                PeriodicTrigger periodicTrigger = (PeriodicTrigger)trigger;
                return (ScheduledTasksEndpoint.TaskDescription)(periodicTrigger.isFixedRate() ? new ScheduledTasksEndpoint.FixedRateTaskDescription(triggerTask, periodicTrigger) : new ScheduledTasksEndpoint.FixedDelayTaskDescription(triggerTask, periodicTrigger));
            } else {
                return null;
            }
        }

It would be great if there were a mechanism for custom SchedulingConfigurer's to show up in the endpoint, but since there isn't one yet, the endpoint should perhaps just ignore them rather than throwing an exception.