flowable/flowable-engine · error · ActivitiIllegalArgumentException

Priority does not resolve to a number: %s

Error message

Priority does not resolve to a number: %s

What it means

Thrown when a user task's priority expression resolves to a non-null String that cannot be parsed as an Integer. The behavior parses String values with Integer.valueOf and wraps NumberFormatException in this ActivitiIllegalArgumentException. The value was a String but not a valid integer.

Source

Thrown at modules/flowable5-engine/src/main/java/org/activiti/engine/impl/bpmn/behavior/UserTaskActivityBehavior.java:177

                            .getProcessEngineConfiguration()
                            .getBusinessCalendarManager()
                            .getBusinessCalendar(taskDefinition.getBusinessCalendarNameExpression().getValue(execution).toString());
                    task.setDueDate(businessCalendar.resolveDuedate((String) dueDate));
                } else {
                    throw new ActivitiIllegalArgumentException("Due date expression does not resolve to a Date or Date string: " +
                            activeDueDateExpression.getExpressionText());
                }
            }
        }

        if (activePriorityExpression != null) {
            final Object priority = activePriorityExpression.getValue(execution);
            if (priority != null) {
                if (priority instanceof String) {
                    try {
                        task.setPriority(Integer.valueOf((String) priority));
                    } catch (NumberFormatException e) {
                        throw new ActivitiIllegalArgumentException("Priority does not resolve to a number: " + priority, e);
                    }
                } else if (priority instanceof Number) {
                    task.setPriority(((Number) priority).intValue());
                } else {
                    throw new ActivitiIllegalArgumentException("Priority expression does not resolve to a number: " +
                            activePriorityExpression.getExpressionText());
                }
            }
        }

        if (activeCategoryExpression != null) {
            final Object category = activeCategoryExpression.getValue(execution);
            if (category != null) {
                if (category instanceof String) {
                    task.setCategory((String) category);
                } else {
                    throw new ActivitiIllegalArgumentException("Category expression does not resolve to a string: " +
                            activeCategoryExpression.getExpressionText());

View on GitHub (pinned to d6d39ce1c6)

Solutions

1. Store the priority as an integer (1-100 per convention) in the process variable, e.g. execution.setVariable("priority", 75).
2. If the variable is a string, convert with a valid integer value first: Integer.parseInt(trimmed) or use an expression like ${integer(priority)} if a converter is available.
3. Map enum labels ("high"/"low") to numbers before the user task, e.g. in a service task or via a start-form default.
4. Example fix

Example fix

// before
execution.setVariable("priority", "high");
<userTask activiti:priority="${priority}"/>
// after
execution.setVariable("priority", 90);
<userTask activiti:priority="${priority}"/>

Object p = execution.getVariable("priority");
if (p instanceof String && !((String) p).trim().matches("-?\\d+")) {
    throw new IllegalArgumentException("priority must be an integer string, got: " + p);
}
if (p != null && !(p instanceof Number) && !(p instanceof String)) {
    throw new IllegalArgumentException("priority must be Number or numeric String");
}

static boolean isValidPriority(Object v) {
    if (v == null) return true;
    if (v instanceof Number) return true;
    if (v instanceof String) {
        try { Integer.parseInt(((String) v).trim()); return true; }
        catch (NumberFormatException e) { return false; }
    }
    return false;
}

try {
    taskService.complete(taskId);
} catch (ActivitiIllegalArgumentException e) {
    if (e.getMessage().startsWith("Priority does not resolve to a number")) {
        Object p = runtimeService.getVariable(executionId, "priority");
        log.error("priority='{}' is not an integer; map labels to ints before the task", p);
    }
    throw e;
}

When it happens

Trigger: activiti:priority expression like ${priorityVar} where priorityVar is a String such as "high", "75.5", "100 ", or any non-integer text; Integer.valueOf throws NumberFormatException and it is rethrown as this error.

Common situations: Form/JSON variables storing priority as words ("high"/"low"), decimal numbers, or values with whitespace/sign issues; mapping a UI enum label straight into the priority expression.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• Priority does not resolve to a number: + priority
• Priority does not resolve to a number:
• Priority expression does not resolve to a number: + activeTa
• Due date expression does not resolve to a Date or Date strin
• Priority expression does not resolve to a number: %s

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/e74933505e75dbf1. Report an issue: GitHub.