flowable/flowable-engine · error · FlowableEventJsonException

Error writing event json

Error message

Error writing event json

What it means

EventJsonConverter.convertToJson serializes an EventModel (including payload and extension properties) into its JSON string. A failure in objectMapper.writeValueAsString is wrapped as FlowableEventJsonException('Error writing event json'). It indicates the event model cannot be represented as JSON.

Solutions

1. Inspect the cause exception to identify which model field/property fails serialization.
2. Fix the EventModel: remove or type-correct the offending payload/extension property values.
3. Ensure the ObjectMapper used (from the supplier) is correctly configured for the model classes.

Example fix

// before
String json = converter.convertToJson(eventModel); // throws on bad extension property
// after
EventPayload payload = eventModel.getPayload();
payload.getExtensionProperties().remove("brokenProperty");
String json = converter.convertToJson(eventModel);

if (eventModel == null || eventModel.getKey() == null) {
    throw new IllegalArgumentException("EventModel and its key must be set before serializing");
}

boolean isSerializable(EventModel m) {
    return m != null && m.getKey() != null && !m.getKey().isEmpty();
}

try {
    String json = converter.convertToJson(eventModel);
} catch (FlowableEventJsonException e) {
    LOG.error("Failed to serialize event model: {}", e.getCause() != null ? e.getCause().getMessage() : e.getMessage());
    throw e;
}

When it happens

Trigger: Calling convertToJson with an EventModel holding unserializable field values (e.g. problematic extension property nodes), or an ObjectMapper failure writing the ObjectNode tree.

Common situations: Custom EventModel subclasses with fields Jackson cannot serialize, corrupt in-memory model built programmatically, or ObjectMapper configuration issues when caching event definitions.

Understand the failure class

Background: json.Marshal / "failed to marshal" errors in Go: why "unsupported type" happens and how to fix it — this error's family across 22 libraries.

Related errors

• An error occurs converting output value as JSon
• Cannot convert event payload
• Could not read json event payload
• Error reading event json
• Error writing app model to json

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/5f449dc1161cb0c2. Report an issue: GitHub.

Appendix: source

Thrown at modules/flowable-event-registry-json-converter/src/main/java/org/flowable/eventregistry/json/converter/EventJsonConverter.java:146

                }

                if (eventPayload.isMetaParameter()) {
                    eventPayloadNode.put("metaParameter", true);
                }
                
                if (eventPayload.getExtensionProperties() != null && !eventPayload.getExtensionProperties().isEmpty()) {
                    ObjectNode extensionPropNode = eventPayloadNode.putObject("extensionProperties");
                    for (String propName : eventPayload.getExtensionProperties().keySet()) {
                        extensionPropNode.put(propName, eventPayload.getExtensionProperties().get(propName));
                    }
                }
            }
        }

        try {
            return objectMapper.writeValueAsString(modelNode);
        } catch (Exception e) {
            throw new FlowableEventJsonException("Error writing event json", e);
        }
    }
    
    protected void processExtensionProperties(JsonNode node, EventPayload payload) {
        JsonNode extensionNodes = node.path("extensionProperties");
        if (extensionNodes != null && !extensionNodes.isMissingNode()) {
            Map<String, String> extensionPropertyMap = new HashMap<>();
            for (String extensionName : extensionNodes.propertyNames()) {
                extensionPropertyMap.put(extensionName, extensionNodes.get(extensionName).asString());
            }
            
            payload.setExtensionProperties(extensionPropertyMap);
        }
    }
}

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