flowable/flowable-engine · error · FlowableIllegalArgumentException

Unsupported variable query operation:

Error message

Unsupported variable query operation: 

What it means

The default branch of the variable-operation switch in HistoricTaskInstanceBaseResource.addTaskVariables rejects any QueryVariableOperation that is not one of the explicitly handled cases (EQUALS, NOT_EQUALS, IGNORE_CASE variants, LIKE variants, GREATER_THAN, etc.). An unknown or out-of-range operation value cannot be mapped to a taskInstanceQuery method, so FlowableIllegalArgumentException is thrown.

Source

Thrown at modules/flowable-cmmn-rest/src/main/java/org/flowable/cmmn/rest/service/api/history/task/HistoricTaskInstanceBaseResource.java:409

            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. Fix the variableOperation value to one of the supported enum names (EQUALS, NOT_EQUALS, EQUALS_IGNORE_CASE, NOT_EQUALS_IGNORE_CASE, LIKE, LIKE_IGNORE_CASE, GREATER_THAN, GREATER_THAN_OR_EQUALS, LESS_THAN, LESS_THAN_OR_EQUALS, EXISTS, NOT_EXISTS).
2. Align client library version with the Flowable server version.
3. Validate the operation client-side against the enum before sending the request.
4. Catch FlowableIllegalArgumentException and log the offending operation for diagnosis.

Example fix

// before
{"name": "status", "value": "open", "variableOperation": "CONTAINS"}
// after
{"name": "status", "value": "open", "variableOperation": "EQUALS"}

Set<String> allowed = Set.of("EQUALS","NOT_EQUALS","EQUALS_IGNORE_CASE","NOT_EQUALS_IGNORE_CASE","LIKE","LIKE_IGNORE_CASE","GREATER_THAN","GREATER_THAN_OR_EQUALS","LESS_THAN","LESS_THAN_OR_EQUALS","EXISTS","NOT_EXISTS");
if (!allowed.contains(variableOperation)) throw new IllegalArgumentException("Unsupported variableOperation: " + variableOperation);

try { return queryTasks(variableFilters); } catch (FlowableIllegalArgumentException e) { if (e.getMessage().startsWith("Unsupported variable query operation")) { /* fix enum in client config */ } throw e; }

When it happens

Trigger: GET /cmmn-history/historic-task-instances with a task variable filter whose variableOperation does not match any known QueryVariableOperation enum value (e.g. a typo like 'EQUALSS' or an operation from a newer Flowable version not present in this release).

Common situations: Client SDKs out of sync with server version; hand-written query strings with misspelled operations; copy-pasted operations from task-runtime endpoints not supported by this historic-query handler.

Related errors

• Unsupported variable query operation: ${variable.getVariable
• Only string variable values are supported using like, but wa
• Variable operation is missing for variable:
• Variable value is missing for variable:
• Variable operation is missing for variable: ${name}

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/a941b46c43a3cc4b. Report an issue: GitHub.