What causes "'?' can only be specfied for Day-of-Month -OR- Day-of-Week." in alibaba/spring-cloud-alibaba?

Set exactly one day field to a real value and the other to '?': e.g. '0 0 0 * * ?' (every day via DOM='*') or '0 0 0 ? * *' (every day via DOW='*').

alibaba/spring-cloud-alibaba · error · ParseException

'?' can only be specfied for Day-of-Month -OR- Day-of-Week.

Error message

'?' can only be specfied for Day-of-Month -OR- Day-of-Week.

What it means

Thrown while parsing the DAY_OF_WEEK '?' token when the DAY_OF_MONTH field was also set to '?' (NO_SPEC). Quartz requires exactly one of the two day fields to be '?' and the other to carry a value; setting '?' for both is illegal. ParseException message: "'?' can only be specified for Day-of-Month -OR- Day-of-Week."

Source

Thrown at spring-cloud-alibaba-starters/spring-cloud-starter-alibaba-schedulerx/src/main/java/com/alibaba/cloud/scheduling/schedulerx/util/CronExpression.java:399

			return (i + 3);
		}

		if (c == '?') {
			i++;
			if ((i + 1) < s.length()
					&& (s.charAt(i) != ' ' && s.charAt(i + 1) != '\t')) {
				throw new ParseException("Illegal character after '?': "
						+ s.charAt(i), i);
			}
			if (type != DAY_OF_WEEK && type != DAY_OF_MONTH) {
				throw new ParseException(
						"'?' can only be specfied for Day-of-Month or Day-of-Week.",
						i);
			}
			if (type == DAY_OF_WEEK && !lastdayOfMonth) {
				final int val = daysOfMonth.last();
				if (val == NO_SPEC_INT) {
					throw new ParseException(
							"'?' can only be specfied for Day-of-Month -OR- Day-of-Week.",
							i);
				}
			}

			addToSet(NO_SPEC_INT, -1, 0, type);
			return i;
		}

		if (c == '*' || c == '/') {
			if (c == '*' && (i + 1) >= s.length()) {
				addToSet(ALL_SPEC_INT, -1, incr, type);
				return i + 1;
			}
			else if (c == '/'
					&& ((i + 1) >= s.length() || s.charAt(i + 1) == ' ' || s
					.charAt(i + 1) == '\t')) {
				throw new ParseException("'/' must be followed by an integer.", i);

View on GitHub (pinned to 115d590110)

Solutions

Set exactly one day field to a real value and the other to '?': e.g. '0 0 0 * * ?' (every day via DOM='*') or '0 0 0 ? * *' (every day via DOW='*').
If you want 'every day', use '*' for day-of-month and '?' for day-of-week.
Validate at config load.

Example fix

# before ('?' in both day fields)
0 0 0 ? * ?

# after (every day: DOM='*', DOW='?')
0 0 0 * * ?

Defensive patterns

Strategy: try-catch

Validate before calling

static String validateCron(String cron) throws ParseException {
    new com.alibaba.cloud.scheduling.schedulerx.util.CronExpression(cron);
    return cron;
}

Type guard

// exactly one of DOM(3)/DOW(5) must be '?'
static boolean exactlyOneDayFieldIsQ(String[] f) {
    if (f.length < 6) return false;
    boolean a = "?".equals(f[3]);
    boolean b = "?".equals(f[5]);
    return a ^ b;
}

Try / catch

try {
    new CronExpression(cron);
} catch (ParseException e) {
    // "'?' can only be specified for Day-of-Month -OR- Day-of-Week."
    log.error("Use '?' for only ONE day field in cron '{}'", cron);
}

Prevention

Rule: one day field gets a value, the other gets '?' — never both '?'.
For 'every day', prefer '* * ?' over '? * ?'.

When it happens

Trigger: An expression with '?' in both day positions, e.g. '0 0 0 ? * ?'. When processing the DOW '?' the parser reads daysOfMonth.last(); if that value is NO_SPEC_INT (98, meaning DOM was also '?') it throws at CronExpression.java:397-401.

Common situations: Using '? * ?' pattern thinking '?' means 'ignore both'; converting from a dialect that allows '?' in both; a template that defaults both day fields to '?'.

Related errors

AI-assisted analysis of alibaba/spring-cloud-alibaba@115d590110 (2026-08-14). Data as JSON: /api/errors/6cc68ac6fe1b0065. Report an issue: GitHub.