flowable/flowable-engine · error · FlowableIllegalArgumentException

Only string variable values are supported when ignoring casi

Error message

Only string variable values are supported when ignoring casing, but was: 

What it means

The historic task variable query used a variable filter with EQUALS_IGNORE_CASE on a value that is not a String; case-insensitive comparison is only defined for string values, so the non-string value's class is reported.

Source

Thrown at modules/flowable-rest/src/main/java/org/flowable/rest/service/api/history/HistoricTaskInstanceBaseResource.java:383

                break;

            case EQUALS_IGNORE_CASE:
                if (actualValue instanceof String) {
                    taskInstanceQuery.taskVariableValueEqualsIgnoreCase(variable.getName(), (String) actualValue);
                } else {
                    throw new FlowableIllegalArgumentException("Only string variable values are supported when ignoring casing, but was: " + actualValue.getClass().getName());
                }
                break;

            case NOT_EQUALS:
                taskInstanceQuery.taskVariableValueNotEquals(variable.getName(), actualValue);
                break;

            case NOT_EQUALS_IGNORE_CASE:
                if (actualValue instanceof String) {
                    taskInstanceQuery.taskVariableValueNotEqualsIgnoreCase(variable.getName(), (String) actualValue);
                } else {
                    throw new FlowableIllegalArgumentException("Only string variable values are supported when ignoring casing, but was: " + actualValue.getClass().getName());
                }
                break;

            case GREATER_THAN:
                taskInstanceQuery.taskVariableValueGreaterThan(variable.getName(), actualValue);
                break;

            case GREATER_THAN_OR_EQUALS:
                taskInstanceQuery.taskVariableValueGreaterThanOrEqual(variable.getName(), actualValue);
                break;

            case LESS_THAN:
                taskInstanceQuery.taskVariableValueLessThan(variable.getName(), actualValue);
                break;

            case LESS_THAN_OR_EQUALS:
                taskInstanceQuery.taskVariableValueLessThanOrEqual(variable.getName(), actualValue);
                break;

View on GitHub (pinned to d6d39ce1c6)

Solutions

1. Use 'notEquals' (case-sensitive, type-aware) for non-string values
2. Quote the value in JSON so it is a String when ignore-case semantics are truly needed
3. Ensure the historic variable is stored as a string if case-insensitive comparison is a requirement

Example fix

// before
{"name":"state","operation":"notEqualsIgnoreCase","value":42}
// after
{"name":"state","operation":"notEquals","value":42}

if (!(variable.getValue() instanceof String))
    throw new IllegalArgumentException("notEqualsIgnoreCase requires a String value");

boolean isStringFilter(QueryVariable v) { return v.getValue() instanceof String; }

try { queryTaskVariables(vars); }
catch (FlowableIllegalArgumentException e) { /* fall back to notEquals */ }

When it happens

Trigger: POST /query/historic-tasks with a taskVariables entry using operation 'notEqualsIgnoreCase' and a non-string value (number, boolean, date).

Common situations: Unquoted JSON numbers; client reusing ignore-case operator for a numeric exclusion filter; value converted to Integer by the REST variable factory.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

• Only string variable values are supported when ignoring casi
• Only string variable values are supported using like, but wa
• Only string variable values are supported when ignoring casi
• Variable operation is missing for variable: " + variable.get
• Variable value is missing for variable: " + variable.getName

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/7fdefa85ccc4273b. Report an issue: GitHub.