flowable/flowable-engine · error · FlowableIllegalArgumentException

Cannot convert event payload ${payloadInstanceValue} to type

Error message

Cannot convert event payload ${payloadInstanceValue} to type 'boolean'

What it means

FlowableIllegalArgumentException thrown by EventPayloadToJsonStringSerializer.serialize when a payload instance declared as type 'boolean' is neither a Boolean nor a String, so it cannot be converted to a JSON boolean during serialization.

Source

Thrown at modules/flowable-event-registry/src/main/java/org/flowable/eventregistry/impl/serialization/EventPayloadToJsonStringSerializer.java:101

                } else if (EventPayloadTypes.LONG.equals(definitionType)) {

                    if (payloadInstanceValue instanceof Number) {
                        objectNode.put(payloadInstance.getDefinitionName(), ((Number) payloadInstanceValue).longValue());
                    } else if (payloadInstanceValue instanceof String) {
                        objectNode.put(payloadInstance.getDefinitionName(), Long.valueOf((String) payloadInstanceValue));
                    } else {
                        throw new FlowableIllegalArgumentException("Cannot convert event payload " + payloadInstanceValue + " to type 'long'");
                    }

                } else if (EventPayloadTypes.BOOLEAN.equals(definitionType)) {

                    if (payloadInstanceValue instanceof Boolean) {
                        objectNode.put(payloadInstance.getDefinitionName(), (Boolean) payloadInstanceValue);
                    } else if (payloadInstanceValue instanceof String) {
                        objectNode.put(payloadInstance.getDefinitionName(), Boolean.valueOf((String) payloadInstanceValue));
                    }  else {
                        throw new FlowableIllegalArgumentException("Cannot convert event payload " + payloadInstanceValue + " to type 'boolean'");
                    }

                } else if (EventPayloadTypes.JSON.equals(definitionType)) {
                    Object jsonValue = payloadInstanceValue;
                    if (payloadInstanceValue instanceof Supplier<?>) {
                        Object suppliedValue = ((Supplier<?>) payloadInstanceValue).get();
                        JsonNode jsonNode = JsonUtil.asJsonNode(suppliedValue, objectMapper, true);
                        if (jsonNode != null) {
                            jsonValue = jsonNode;
                        }
                    } else {
                        JsonNode jsonNode = JsonUtil.asJsonNode(jsonValue, objectMapper, true);
                        if (jsonNode != null) {
                            jsonValue = jsonNode;
                        }
                    }
                    if (jsonValue instanceof JsonNode) {
                        objectNode.set(payloadInstance.getDefinitionName(), (JsonNode) jsonValue);

View on GitHub (pinned to d6d39ce1c6)

Solutions

1. Set the payload value as a Boolean (or boolean-parseable String like "true"/"false").
2. Convert numeric flags (0/1) to Boolean before publishing.
3. Change the payload definition type if the value is not boolean-like.

Example fix

// before
payload.put("active", resultSet.getInt("active")); // 0/1 int
// after
payload.put("active", resultSet.getInt("active") == 1);

Object v = payloadValue; if (!(v instanceof Boolean) && !(v instanceof String)) { throw new IllegalArgumentException("payload 'boolean' value must be Boolean or String"); }

boolean isBooleanCompatible(Object v) { return v instanceof Boolean || v instanceof String; }

try { serializer.serialize(eventInstance); } catch (FlowableIllegalArgumentException e) { LOG.error("payload type mismatch for boolean field: " + e.getMessage()); throw e; }

When it happens

Trigger: Payload definition declares type 'boolean' but the instance value is an incompatible object (Number, Map, POJO) at serialize time.

Common situations: Flags set as Integer 0/1 from database rows; config-driven payloads using non-Boolean types; schema changes without producer updates.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

• Cannot convert event payload ${payloadInstanceValue} to type
• Cannot convert event payload ${payloadInstanceValue} to type
• Cannot convert event payload ${payloadInstanceValue} to type
• Cannot convert event payload ${jsonValue} to type 'json'
• Could not read json event payload

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/ad9f7fe5c1f4d168. Report an issue: GitHub.