flowable/flowable-engine · error · FlowableIllegalArgumentException

Value-only query (without a variable-name) is not supported.

Error message

Value-only query (without a variable-name) is not supported.

What it means

A nameless (value-only) variable filter, where only the value is supplied, is rejected for historic task queries. Flowable requires a variable name on every task variable query predicate and throws FlowableIllegalArgumentException.

Source

Thrown at modules/flowable-rest/src/main/java/org/flowable/rest/service/api/history/HistoricTaskInstanceBaseResource.java:358

    protected void addTaskVariables(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);

            // 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);

View on GitHub (pinned to d6d39ce1c6)

Solutions

1. Always include the variable 'name' in the filter object
2. Remove the value-only entry and use a different search mechanism (e.g. query by process variables at process level if supported)
3. Validate the request body client-side before posting

Example fix

// before
{"taskVariables":[{"operation":"equals","value":"foo"}]}
// after
{"taskVariables":[{"name":"myVar","operation":"equals","value":"foo"}]}

if (variable.getName() == null)
    throw new IllegalArgumentException("variable name required in historic task query filter");

When it happens

Trigger: POST query on historic task instances with a taskVariables entry that has a value but no 'name' property (variable.getName()==null) in addTaskVariables.

Common situations: Client assumes value-only search like some other query APIs support; JSON body builder drops empty name field; template expansion left name blank.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

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

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/d85c8e27acb62383. Report an issue: GitHub.