Java String Property Values that Start with a Single Number are Truncated

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Introduction

When trying to parameterize a Spring Task's CRON Schedule using environment variables, I hit a problem where the full schedule was not being received from the properties, but only in the cases where the first value was a number. Searching Google gave me zero examples of my type of problem, so I was on my own.

The solution I found involves using a separate environment variable for each section of the schedule.

Using the Code

The attached Maven-based project is a simple one where a Spring Task will print out the current time to the console. I use Intellij's IDEA, but you should be able to adapt this to Eclipse, or really any other IDE of your liking.

The task class is:

public class ScheduledTasks {

    private static final Logger log = LoggerFactory.getLogger(ScheduledTasks.class);

    private static final SimpleDateFormat dateFormat = new SimpleDateFormat("HH:mm:ss");

    @Scheduled(cron ="${cron.schedule}")
    public void reportCurrentTime() {
        log.info("The time is now {}", dateFormat.format(new Date()));
    }
}

In my application.properties, I originally set the schedule from a single Environment Variable:

cron.schedule = ${test_cron}

If I run this with CRON schedule of "*/5 * * * * ?" (every 5 seconds) set in the Environment Variable "test_cron", I get the expected outcome:

2021-04-29 12:17:50.437  INFO 22420 --- [           main] o.s.s.c.ThreadPoolTaskScheduler
          : Initializing ExecutorService 'taskScheduler'
2021-04-29 12:17:50.480  INFO 22420 --- [           main] c.e.s.SchedulingTasksApplication
         : Started SchedulingTasksApplication in 2.441 seconds (JVM running for 3.931)
2021-04-29 12:17:55.008  INFO 22420 --- [   scheduling-1] c.e.schedulingtasks.ScheduledTasks
       : The time is now 12:17:55
2021-04-29 12:18:00.014  INFO 22420 --- [   scheduling-1] c.e.schedulingtasks.ScheduledTasks
       : The time is now 12:18:00
2021-04-29 12:18:05.005  INFO 22420 --- [   scheduling-1] c.e.schedulingtasks.ScheduledTasks
       : The time is now 12:18:05

But if I run it with a schedule of "0 25 * * * ?" (at 25 minutes past the hour), I get an error saying my schedule is invalid and only has a zero in it:

Encountered invalid @Scheduled method 'reportCurrentTime': For input string: ""0"

To get around this, I altered the application properties to use one Environment variable per schedule section, with a space between:

cron.schedule = ${cron_sec} ${cron_min} ${cron_hr} ${cron_day} ${cron_mth} ${cron_wk}

And ran this with each environment variable set to the needed value. Similar example to the failed one above:

cron_sec=0
cron_min=30
cron_hr=*
cron_day=*
cron_mth=*
cron_wk=*

With which I get the expected output:

2021-04-29 12:29:25.539  INFO 22896 --- [           main] c.e.s.SchedulingTasksApplication
         : Started SchedulingTasksApplication in 3.677 seconds (JVM running for 5.441)
2021-04-29 12:30:00.003  INFO 22896 --- [   scheduling-1] c.e.schedulingtasks.ScheduledTasks
       : The time is now 12:30:00

If this helps even one other person with this type of problem, then my work is done! :)

Points of Interest

As mentioned, Google was of completely zero help with this problem. I could find nothing related to truncation of Application.properties String values that start with a number followed by a space. Is this a bug or "feature" of Java? I'll let you decide!

History

• v1 - 29^th April, 2021