flowable/flowable-engine · error · ParseException

Unexpected end of string.

Error message

Unexpected end of string.

What it means

Thrown when a '/' increment marker is found and the parser advances past it (i++) but there are no characters left: i >= s.length(). Same intent as the previous check but covers the exact end-of-string case where '/' is the last character of the entire expression.

Solutions

1. Complete the increment: '/5' instead of trailing '/'.
2. Check the storage/config layer for silent truncation (column size, .properties line handling, trim logic).
3. Log the raw expression length and content when ParseException occurs to spot truncation.
4. Add a startup validation pass over all configured cron expressions.

Example fix

// before
new CronExpression("0 0 12 * */");
// after
new CronExpression("0 0 12 * */2");

String trimmed = expr.trim();
if (trimmed.endsWith("/")) {
    throw new IllegalArgumentException("Cron expression ends with '/': " + expr);
}

try {
    new CronExpression(expr);
} catch (java.text.ParseException e) {
    if (e.getMessage().contains("Unexpected end of string")) {
        log.error("Cron truncated (len={}): '{}'", expr.length(), expr);
    }
}

When it happens

Trigger: new CronExpression("0 0 12 * */") — expression ends immediately after '/'; truncation in property files, database columns with limited length, or log/console copy-paste cutting the tail.

Common situations: VARCHAR/property length truncation silently cutting the cron string; copy-paste missing the final token; string-splitting code that drops the last field's step.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

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

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/1b2fd7a3e69c3357. Report an issue: GitHub.

Appendix: source

Thrown at modules/flowable-engine-common/src/main/java/org/flowable/common/engine/impl/calendar/CronExpression.java:644

            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?
                i++;
                if (i >= s.length()) {
                    throw new ParseException("Unexpected end of string.", i);
                }

                incr = getNumericValue(s, i);

                i++;
                if (incr > 10) {
                    i++;
                }
                checkIncrementRange(incr, type, i);
            } else {
                incr = 1;
            }

            addToSet(ALL_SPEC_INT, -1, incr, type);
            return i;
        } else if (c == 'L') {
            i++;
            if (type == DAY_OF_MONTH) {

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