flowable/flowable-engine · error · FlowableIllegalArgumentException

Cannot convert event payload ${payloadInstanceValue} to type

Error message

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

What it means

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

Source

Thrown at modules/flowable-event-registry/src/main/java/org/flowable/eventregistry/impl/serialization/EventPayloadToJsonStringSerializer.java:81

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

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

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

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

                } 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));

View on GitHub (pinned to d6d39ce1c6)

Solutions

Set the payload value as an Integer/Number (or integer-parseable String) matching the 'integer' definition.
Change the payload definition type if the value is not truly an integer.
Coerce and validate values before event publication.

Example fix

// before
payload.put("count", someObject); // e.g. a Map
// after
payload.put("count", Integer.parseInt(someObject.toString()));

Defensive patterns

Strategy: type-guard

Validate before calling

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

Type guard

boolean isIntegerCompatible(Object v) { return v instanceof Number || v instanceof String; }

Try / catch

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

Prevention

Use Integer/Long values for integer-typed payloads
Avoid putting Maps/POJOs into numeric payload fields
Add unit tests asserting payload types against definitions

When it happens

Trigger: Payload definition declares type 'integer' but the instance value is an incompatible object (Boolean, Map, POJO, Double-like non-Number, etc.) at serialize time.

Common situations: Publishing events with values of the wrong Java type; loosely typed map-based payload construction; schema changed from string to integer without updating producers.

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

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/75af8c19e0da2846. Report an issue: GitHub.