flowable/flowable-engine · error · FlowableIllegalArgumentException

Illegal action: ' '.

Error message

Illegal action: '${action}'.

What it means

FlowableIllegalArgumentException thrown by ExecutionCollectionResource.executeExecutionAction when the ExecutionActionRequest 'action' is anything other than 'signal-event-received' — the only action this collection-level endpoint supports. This endpoint signals the whole process instance via a signal event; other execution actions must go through the single-execution endpoint.

Solutions

1. Set action to exactly "signal-event-received" in the request body.
2. Use the per-execution endpoint POST /runtime/executions/{executionId} instead if you need 'trigger' or 'message-event-received' actions.
3. Check for typos/casing: the value is kebab-case and case-sensitive.
4. Consult the ExecutionActionRequest.ACTION_SIGNAL_EVENT_RECEIVED constant for the canonical value.

Example fix

// before
{"action": "message-event-received", "messageName": "orderMsg"}
// after
{"action": "signal-event-received", "signalName": "orderSignal"}

const ALLOWED_ACTIONS = ['signal-event-received']; // collection endpoint supports only this
if (!ALLOWED_ACTIONS.includes(body.action)) {
  throw new Error(`POST /runtime/executions only supports action "signal-event-received", got "${body.action}"`);
}

function isSignalAction(a: unknown): a is 'signal-event-received' {
  return a === 'signal-event-received';
}

try {
  await restClient.post('/runtime/executions', body);
} catch (e) {
  if (e.response && e.response.status === 400 && /Illegal action/.test(e.response.data && e.response.data.message || '')) {
    console.error(`Unsupported action "${body.action}" for this endpoint; use the per-execution endpoint for trigger/message actions`);
  }
  throw e;
}

When it happens

Trigger: POST /runtime/executions with body {"action":"..."} where action is not "signal-event-received" (e.g. "message-event-received", "trigger", or a typo like "signalEventReceived").

Common situations: Copying action strings from code that targets the per-execution endpoint (which allows trigger/message actions); camelCase vs kebab-case confusion with ExecutionActionRequest.ACTION_* constants; using old Activiti-style action names.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• A request body was expected when executing the form submit.
• Attachment name is required.
• Error converting request body to RestVariable instance
• Id cannot be null.
• Invalid action: ' '.

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/820481daf0432673. Report an issue: GitHub.

Appendix: source

Thrown at modules/flowable-rest/src/main/java/org/flowable/rest/service/api/runtime/process/ExecutionCollectionResource.java:145

        return getQueryResponse(queryRequest, allRequestParams);
    }

    //FIXME Documentation ?
    @ApiOperation(value = "Signal event received", tags = { "Executions" }, code = 204)
    @ApiResponses(value = {
            @ApiResponse(code = 204, message = "Indicates request was successful and the executions are returned"),
            @ApiResponse(code = 404, message = "Indicates a parameter was passed in the wrong format . The status-message contains additional information.")
    })
    @PutMapping(value = "/runtime/executions")
    @ResponseStatus(HttpStatus.NO_CONTENT)
    public void executeExecutionAction(@RequestBody ExecutionActionRequest actionRequest) {
        if (restApiInterceptor != null) {
            restApiInterceptor.doExecutionActionRequest(actionRequest);
        }
        
        if (!ExecutionActionRequest.ACTION_SIGNAL_EVENT_RECEIVED.equals(actionRequest.getAction())) {
            throw new FlowableIllegalArgumentException("Illegal action: '" + actionRequest.getAction() + "'.");
        }

        if (actionRequest.getSignalName() == null) {
            throw new FlowableIllegalArgumentException("Signal name is required.");
        }

        if (actionRequest.getVariables() != null) {
            runtimeService.signalEventReceived(actionRequest.getSignalName(), getVariablesToSet(actionRequest.getVariables()));
        } else {
            runtimeService.signalEventReceived(actionRequest.getSignalName());
        }
    }
}

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