flowable/flowable-engine · error · FlowableIllegalArgumentException

Unsupported variable query operation:

Error message

Unsupported variable query operation: 

What it means

Thrown by addTaskVariables in HistoricTaskInstanceBaseResource when a task variable query predicate uses a QueryVariableOperation that the historic task instance query cannot map to a taskVariable* method. The switch only handles EQUALS, NOT_EQUALS, EQUALS_IGNORE_CASE, NOT_EQUALS_IGNORE_CASE, LIKE, LIKE_IGNORE_CASE, GREATER_THAN(_OR_EQUALS), LESS_THAN(_OR_EQUALS), EXISTS and NOT_EXISTS; anything else hits the default branch. This means the REST request supplied an operation value outside the supported set.

Source

Thrown at modules/flowable-rest/src/main/java/org/flowable/rest/service/api/history/HistoricTaskInstanceBaseResource.java:428

            case LIKE_IGNORE_CASE:
                if (actualValue instanceof String) {
                    taskInstanceQuery.taskVariableValueLikeIgnoreCase(variable.getName(), (String) actualValue);
                } else {
                    throw new FlowableIllegalArgumentException("Only string variable values are supported using like, but was: " + actualValue.getClass().getName());
                }
                break;

            case EXISTS:
                taskInstanceQuery.taskVariableExists(variable.getName());
                break;

            case NOT_EXISTS:
                taskInstanceQuery.taskVariableNotExists(variable.getName());
                break;

            default:
                throw new FlowableIllegalArgumentException("Unsupported variable query operation: " + variable.getVariableOperation());
            }
        }
    }

    protected void addProcessVariables(HistoricTaskInstanceQuery taskInstanceQuery, List<QueryVariable> variables) {
        for (QueryVariable variable : variables) {
            if (variable.getVariableOperation() == null) {
                throw new FlowableIllegalArgumentException("Variable operation is missing for variable: " + variable.getName());
            }
            if (variable.getVariableOperation() != QueryVariableOperation.EXISTS && variable.getVariableOperation() != QueryVariableOperation.NOT_EXISTS) {
                if (variable.getValue() == null) {
                    throw new FlowableIllegalArgumentException("Variable value is missing for variable: " + variable.getName());
                }
            }

            boolean nameLess = variable.getName() == null;

            Object actualValue = restResponseFactory.getVariableValue(variable);

View on GitHub (pinned to d6d39ce1c6)

Solutions

1. Use one of the supported operations: equals, notEquals, equalsIgnoreCase, notEqualsIgnoreCase, like, likeIgnoreCase, greaterThan, greaterThanOrEquals, lessThan, lessThanOrEquals, exists, notExists.
2. Check spelling/casing of the variable op in the query string; the value must deserialize into QueryVariableOperation.
3. If a genuinely new operation is needed, upgrade Flowable to a version whose addTaskVariables supports it.

Example fix

// before
GET /flowable-rest/history/historic-task-instances?taskVariable=eq==status/active
// after
GET /flowable-rest/history/historic-task-instances?taskVariable=equals==status/active

const OPS = ['equals','notEquals','equalsIgnoreCase','notEqualsIgnoreCase','like','likeIgnoreCase','greaterThan','greaterThanOrEquals','lessThan','lessThanOrEquals','exists','notExists'];
if (!OPS.includes(q.taskVariableOp)) throw new Error('Unsupported task variable op: ' + q.taskVariableOp);

When it happens

Trigger: Calling GET /history/historic-task-instances?taskVariable=op=<operation><name><value> (or POST variant) with an unsupported operation string for a task-scope variable. For example a typo like 'eq' or an operation valid in another endpoint but not in the query-variables mapper.

Common situations: Hand-built query strings with mistyped operation tokens; client code copied from process-variable endpoints; upgrading clients sending new operations an older Flowable REST layer does not recognize.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• Variable operation is missing for variable:
• Variable value is missing for variable:
• Task has no form defined
• Could not find a case instance with id '${caseInstanceId}'.
• Variable operation is missing for variable: ${variable.getNa

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/45d81147945b1294. Report an issue: GitHub.