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: " + actualValue.getClass().getName()

What it means

The equalsIgnoreCase variable comparison in historic task queries only supports String values; Flowable throws FlowableIllegalArgumentException with the actual value's class name when the deserialized value is not a String (e.g. Integer, Boolean, Date).

Source

Thrown at modules/flowable-rest/src/main/java/org/flowable/rest/service/api/history/HistoricTaskInstanceBaseResource.java:371

            Object actualValue = restResponseFactory.getVariableValue(variable);

            // A value-only query is only possible using equals-operator
            if (nameLess) {
                throw new FlowableIllegalArgumentException("Value-only query (without a variable-name) is not supported.");
            }

            switch (variable.getVariableOperation()) {

            case EQUALS:
                taskInstanceQuery.taskVariableValueEquals(variable.getName(), actualValue);
                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;

View on GitHub (pinned to d6d39ce1c6)

Solutions

1. Send the value as a JSON string: {"operation":"equalsIgnoreCase","value":"foo"}
2. For non-string variables switch to the type-specific 'equals'/'notEquals' operations instead of ignore-case variants
3. Convert the variable to a String in the process data if case-insensitive comparison is required

Example fix

// before
{"name":"level","operation":"equalsIgnoreCase","value":5}
// after
{"name":"level","operation":"equals","value":5}
// or keep ignore-case with a string:
{"name":"level","operation":"equalsIgnoreCase","value":"high"}

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

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

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

When it happens

Trigger: POST /query/historic-tasks with a taskVariables entry using operation 'equalsIgnoreCase' whose value deserializes to a non-String type (numeric 5, boolean true, etc.).

Common situations: Client sends unquoted numbers/booleans in JSON; case-insensitive match attempted on an int/long variable; type drift after a variable type changed between versions.

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/67f091a807729f9d. Report an issue: GitHub.