flowable/flowable-engine · error · FlowableIllegalArgumentException

Decision key is required.

Error message

Decision key is required.

What it means

REST request validation in DmnRuleServiceResource.execute: the execute-decision request body did not include a decision key (and no table/definition identifier), so the DMN rule service cannot determine which decision to evaluate.

Solutions

1. Include "decisionKey" in the JSON request body.
2. Validate the request payload on the client before sending.
3. Check client serialization is not omitting the field (e.g. null-skipping serializers with a null value).
4. Catch the 400 response and inspect the error message to confirm which field is missing.

Example fix

// before
POST /dmn-rule/execute {"inputVariables": {"a": 1}}
// after
POST /dmn-rule/execute {"decisionKey": "myDecision", "inputVariables": {"a": 1}}

if (request.getDecisionKey() == null || request.getDecisionKey().isEmpty()) {
    throw new IllegalArgumentException("decisionKey is required");
}

try {
    ResponseEntity<DmnRuleServiceResponse> resp = rest.postForEntity(url, request, DmnRuleServiceResponse.class);
} catch (HttpClientErrorException.BadRequest e) {
    logger.error("decisionKey missing: {}", e.getResponseBodyAsString());
}

When it happens

Trigger: POSTing JSON to /dmn-rule/execute without a decisionKey field, or with decisionKey explicitly set to null.

Common situations: Client payloads missing the field due to serialization settings skipping nulls/defaults; renaming the property in the client while the server expects decisionKey; copy-pasted request templates from other endpoints.

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

• Either caseDefinitionId or caseDefinitionKey is required.
• Variable ' ' has unsupported type: ' '.
• A group or a user is required to create an identity link.
• A group or a user is required to create an identity link.
• A group or a user is required to create an identity link.

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/695819d21ca60ddf. Report an issue: GitHub.

Appendix: source

Thrown at modules/flowable-dmn-rest/src/main/java/org/flowable/dmn/rest/service/api/decision/DmnRuleServiceResource.java:67

    @Autowired
    protected DmnRestResponseFactory dmnRestResponseFactory;

    @Autowired
    protected DmnDecisionService dmnDecisionService;

    @Autowired(required = false)
    protected DmnRestApiInterceptor restApiInterceptor;

    @ApiOperation(value = "Execute a Decision", tags = { "DMN Rule Service" }, code = 201)
    @ApiResponses(value = {
            @ApiResponse(code = 201, message = "Indicates the Decision has been executed")
    })
    @PostMapping(value = "/dmn-rule/execute", produces = "application/json")
    @ResponseStatus(HttpStatus.CREATED)
    public DmnRuleServiceResponse execute(@ApiParam("request") @RequestBody DmnRuleServiceRequest request) {
        if (request.getDecisionKey() == null) {
            throw new FlowableIllegalArgumentException("Decision key is required.");
        }

        if (restApiInterceptor != null) {
            restApiInterceptor.executeDecision(request);
        }

        Map<String, Object> inputVariables = composeInputVariables(request.getInputVariables());

        try {
            ExecuteDecisionBuilder decisionBuilder = dmnDecisionService.createExecuteDecisionBuilder();
            decisionBuilder.decisionKey(request.getDecisionKey()).variables(inputVariables);

            if (StringUtils.isNotEmpty(request.getParentDeploymentId())) {
                decisionBuilder.parentDeploymentId(request.getParentDeploymentId());
            }

            if (StringUtils.isNotEmpty(request.getTenantId())) {
                decisionBuilder.tenantId(request.getTenantId());

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