flowable/flowable-engine · error · FlowableIllegalArgumentException

Value-only query (without a variable-name) is only supported

Error message

Value-only query (without a variable-name) is only supported when using 'equals' operation.

What it means

FlowableIllegalArgumentException for value-only variable queries: omitting the variable name is allowed only with the 'equals' operation, because any other comparator is meaningless without a name to match on.

Source

Thrown at modules/flowable-cmmn-rest/src/main/java/org/flowable/cmmn/rest/service/api/history/caze/HistoricCaseInstanceBaseResource.java:325

    protected void addVariables(HistoricCaseInstanceQuery caseInstanceQuery, 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 && variable.getVariableOperation() != QueryVariableOperation.EQUALS) {
                throw new FlowableIllegalArgumentException("Value-only query (without a variable-name) is only supported when using 'equals' operation.");
            }

            switch (variable.getVariableOperation()) {

            case EQUALS:
                if (nameLess) {
                    caseInstanceQuery.variableValueEquals(actualValue);
                } else {
                    caseInstanceQuery.variableValueEquals(variable.getName(), actualValue);
                }
                break;

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

View on GitHub (pinned to d6d39ce1c6)

Solutions

1. Keep operation "equals" when querying by value only
2. Add a variable "name" if you need like/notEquals/greaterThan semantics
3. Split the query into an equals-by-value request plus follow-up filtering
4. Validate: name==null implies operation must be equals

Example fix

// before
{"value":"abc","operation":"like"}
// after
{"value":"abc","operation":"equals"} // or add "name":"myVar"

if (name == null && !"equals".equals(operation))
  throw new IllegalArgumentException("Value-only query requires equals operation");

boolean validValueOnlyQuery(Map<String,Object> v) {
  return v.get("name") != null || "equals".equals(v.get("operation"));
}

try { ... } catch (FlowableIllegalArgumentException e) {
  return badRequest("Unsupported value-only query: " + e.getMessage());
}

When it happens

Trigger: POST query with {"value":"abc","operation":"like"} (or any non-equals operation) and no "name".

Common situations: Searching for any variable holding a given value: users generalize the pattern and swap equals for like/greaterThan while still omitting name.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

• Variable operation is missing for variable: ${variable.getNa
• Variable value is missing for variable: ${variable.getName()
• Only string variable values are supported when ignoring casi
• Only string variable values are supported for like, but was:
• Variable operation is missing for variable:

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/d08c96c7c199be94. Report an issue: GitHub.