code: public static String extractJobSchedule(JobExecutionInfo jobInfo) {
          if (jobInfo.hasJobProperties() && jobInfo.getJobProperties().size() > 0) {
              StringMap props = jobInfo.getJobProperties();
  
              if (props.containsKey(ConfigurationKeys.JOB_RUN_ONCE_KEY) ||
                      !props.containsKey(ConfigurationKeys.JOB_SCHEDULE_KEY)) {
                  return "RUN_ONCE";
              } else if (props.containsKey(ConfigurationKeys.JOB_SCHEDULE_KEY)) {
                  return props.get(ConfigurationKeys.JOB_SCHEDULE_KEY);
              }
          }
          return "UNKNOWN";
      }
docs: Extracts the schedule from a job execution.
  <p/>
  If the job was in run once mode, it will return that, otherwise it will return the schedule.
  
  @param jobInfo A job execution info to extract from
  @return "RUN_ONCE", the Quartz schedule string, or "UNKNOWN" if there were no job properties