flowable/flowable-engine · error · FlowableIllegalArgumentException

Variable name is required.

Error message

Variable name is required.

What it means

Thrown by composeInputVariables when an entry in the request's inputVariables/variables array has a null name. Each EngineRestVariable must carry a name so it can be mapped into the DMN input map. The whole request is rejected at validation time.

Solutions

1. Ensure every object in inputVariables has a non-null "name" property, e.g. {"name":"amount","value":100}
2. Validate the array client-side before posting (each element has name)
3. Fix key mismatch in variable construction (must be "name", not "key" or "variableName")
4. Log the offending payload to find which variable entry lacks a name

Example fix

// before
{"decisionKey":"d1","inputVariables":[{"value":5}]}
// after
{"decisionKey":"d1","inputVariables":[{"name":"x","value":5}]}

boolean allNamed = request.inputVariables == null ||
    request.inputVariables.stream().allMatch(v -> v.getName() != null);
if (!allNamed) throw new IllegalArgumentException("every inputVariable needs a name");

const namedVars = (vars) => (vars == null || vars.every(v => typeof v.name === 'string' && v.name.length > 0));

try {
    resp = client.executeDecision(req);
} catch (HttpClientErrorException e) {
    if (e.getResponseBodyAsString().contains("Variable name is required")) {
        throw new IllegalArgumentException("an input variable is missing its name", e);
    }
    throw e;
}

When it happens

Trigger: POST to any /dmn-rule/execute-decision(-service)[/single-result] endpoint with an inputVariables array containing an object without a "name" property, e.g. {"inputVariables":[{"value":5}]}.

Common situations: Hand-written JSON missing the name field; variable objects built from generic maps where keys are {name, value} but a different key was used; bulk-converted payloads where one variable lost its name.

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

• File must be of type .dmn
• Invalid body was supplied
• No decision execution id provided
• No deployment id provided
• No variable name was found in request body.

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/375994656eb477d9. Report an issue: GitHub.

Appendix: source

Thrown at modules/flowable-dmn-rest/src/main/java/org/flowable/dmn/rest/service/api/decision/DmnRuleServiceResource.java:318

                decisionBuilder.disableHistory();
            }

            Map<String, Object> executionResult = decisionBuilder.executeDecisionServiceWithSingleResult();

            return dmnRestResponseFactory.createDmnRuleServiceResponse(executionResult);

        } catch (FlowableObjectNotFoundException fonfe) {
            throw new FlowableIllegalArgumentException(fonfe.getMessage(), fonfe);
        }
    }

    protected Map<String, Object> composeInputVariables(List<EngineRestVariable> restVariables) {
        Map<String, Object> inputVariables = null;
        if (restVariables != null) {
            inputVariables = new HashMap<>();
            for (EngineRestVariable variable : restVariables) {
                if (variable.getName() == null) {
                    throw new FlowableIllegalArgumentException("Variable name is required.");
                }
                inputVariables.put(variable.getName(), dmnRestResponseFactory.getVariableValue(variable));
            }
        }
        return inputVariables;
    }
}

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