flowable/flowable-engine · error · ParseException

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

Error message

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

What it means

Thrown when '?' appears in Day-of-Week while Day-of-Month was also set to '?' (daysOfMonth.last() == NO_SPEC_INT). Quartz requires exactly one of the two day fields to have a specific value; if both are '?', the schedule is ambiguous and rejected. Note the parser also requires Day-of-Week '?' only when lastdayOfMonth is false ('L' in DOM).

Source

Thrown at modules/flowable-engine-common/src/main/java/org/flowable/common/engine/impl/calendar/CronExpression.java:623

            if (eval != -1) {
                incr = 1;
            }
            addToSet(sval, eval, incr, type);
            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 specified for Day-of-Month or Day-of-Week.", i);
            }
            if (type == DAY_OF_WEEK && !lastdayOfMonth) {
                int val = daysOfMonth.last();
                if (val == NO_SPEC_INT) {
                    throw new ParseException("'?' can only be specified 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);
            } else if (c == '*') {
                i++;
            }
            c = s.charAt(i);
            if (c == '/') { // is an increment specified?

View on GitHub (pinned to d6d39ce1c6)

Solutions

1. Set one day field to '?': e.g. '0 0 12 ? * MON' or '0 0 12 15 * ?', never both.
2. In expression builders, enforce that exactly one of day-of-month/day-of-week is '?' and the other is '*' or a concrete value.
3. If you want 'every day', use '?' in one field and '*' in the other: '0 0 12 * * ?'.
4. Pre-validate stored cron strings on startup and reject ambiguous ones with a clear message.

Example fix

// before
new CronExpression("0 0 12 ? * ?");
// after
new CronExpression("0 0 12 * * ?");

String[] p = expr.trim().split("\\s+");
if (p.length >= 6 && p[3].equals("?") && p[5].equals("?")) {
    throw new IllegalArgumentException("Day-of-Month and Day-of-Week cannot both be '?': " + expr);
}

try {
    new CronExpression(expr);
} catch (java.text.ParseException e) {
    if (e.getMessage().contains("-OR-")) {
        throw new IllegalArgumentException("Set '?' in only one of Day-of-Month / Day-of-Week: " + expr, e);
    }
}

When it happens

Trigger: new CronExpression("0 0 12 ? * ?") — both day fields are '?'; programmatic builders that default both day fields to '?' without checking the other.

Common situations: Form UIs where both day selectors default to 'any (?)' and the user never touches either; serialization round-trips that lose which field was intentionally specified; template expressions with two placeholders both filled with '?'.

Understand the failure class

Background: Conflicting config options: "cannot be used together" — configuration validation errors across open-source libraries — this error's family across 162 libraries.

Related errors

• Invalid Day-of-Week value: '
• A numeric value between 1 and 5 must follow the '#' option
• Illegal characters for this position: '
• Illegal character after ?:
• '?' can only be specified for Day-of-Month or Day-of-Week.

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/04c24d66c940ebff. Report an issue: GitHub.