flowable/flowable-engine · error · FlowableIllegalArgumentException

Variable value is missing for variable: ${variable.getName()

Error message

Variable value is missing for variable: ${variable.getName()}

What it means

For variable query filters whose operation is not EXISTS/NOT_EXISTS, a value is mandatory because the engine compares against it. addVariables throws FlowableIllegalArgumentException when the operation requires a value but variable.getValue() is null.

Source

Thrown at modules/flowable-cmmn-rest/src/main/java/org/flowable/cmmn/rest/service/api/runtime/caze/BaseCaseInstanceResource.java:308

     * Throws the right exceptions when bad request was made or instance was not found.
     */
    protected CaseInstance getCaseInstanceFromRequestWithoutAccessCheck(String caseInstanceId) {
        CaseInstance caseInstance = runtimeService.createCaseInstanceQuery().caseInstanceId(caseInstanceId).singleResult();
        if (caseInstance == null) {
            throw new FlowableObjectNotFoundException("Could not find a case instance with id '" + caseInstanceId + "'.");
        }

        return caseInstance;
    }

    protected void addVariables(CaseInstanceQuery 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 {

View on GitHub (pinned to d6d39ce1c6)

Solutions

  1. Provide a value for every comparison operation, e.g. {"name":"amount","value":100,"operation":"GREATER_THAN"}.
  2. Use operation EXISTS or NOT_EXISTS when you only want to test variable presence without a value.
  3. Client-side: validate that each non-EXISTS filter has a non-null value before submitting.
  4. Ensure your JSON payload actually serializes the value field.

Example fix

// before
{"name":"amount","operation":"GREATER_THAN"}

// after
{"name":"amount","value":100,"operation":"GREATER_THAN"}
Defensive patterns

Strategy: validation

Validate before calling

vars.forEach(v => {
  if (!['EXISTS','NOT_EXISTS'].includes(v.operation) && v.value == null)
    throw new Error(`Missing value for variable ${v.name}`);
});

Prevention

When it happens

Trigger: Query body variables entry like {"name":"amount","operation":"GREATER_THAN"} (no value), or value explicitly null, on /cmmn-query/runtime/case-instances queries.

Common situations: Building dynamic filters where optional values are dropped, serializers omitting null fields, confusing EXISTS (which needs no value) with comparison operators, or empty-string values converted to null upstream.

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

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/230bc1105865a510. Report an issue: GitHub.