flowable/flowable-engine · error · FlowableIllegalArgumentException

Could not read json event payload

Error message

Could not read json event payload

What it means

FlowableIllegalArgumentException thrown by EventPayloadToJsonStringSerializer.serialize when a payload declared as type 'json' is a String that Jackson cannot parse into a JsonNode (readTree throws JacksonException). The original Jackson exception is attached as cause.

Source

Thrown at modules/flowable-event-registry/src/main/java/org/flowable/eventregistry/impl/serialization/EventPayloadToJsonStringSerializer.java:125

                        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);
                    } else if (jsonValue instanceof String) {
                        JsonNode jsonNode;
                        try {
                            jsonNode = objectMapper.readTree((String) jsonValue);
                        } catch (JacksonException e) {
                            throw new FlowableIllegalArgumentException("Could not read json event payload", e);
                        }
                        objectNode.set(payloadInstance.getDefinitionName(), jsonNode);
                    }  else {
                        throw new FlowableIllegalArgumentException("Cannot convert event payload " + jsonValue + " to type 'json'");
                    }

                } else {
                    throw new FlowableIllegalArgumentException("Unsupported event payload instance type: " + definitionType);
                }

            } else {
                objectNode.putNull(payloadInstance.getDefinitionName());
            }
        }

        try {
            return objectMapper.writeValueAsString(objectNode);
        } catch (JacksonException e) {

View on GitHub (pinned to d6d39ce1c6)

Solutions

1. Fix the JSON string so it parses (validate with objectMapper.readTree before publishing).
2. Pass an already-built JsonNode/ObjectNode instead of a raw String to avoid re-parsing.
3. Check for truncation/encoding issues introduced upstream (size limits, charsets).

Example fix

// before
payload.put("data", "{name: 'x',} "); // invalid JSON
// after
ObjectNode node = objectMapper.createObjectNode();
node.put("name", "x");
payload.put("data", node);

if (jsonString != null) { try { objectMapper.readTree(jsonString); } catch (JacksonException e) { throw new IllegalArgumentException("payload is not valid JSON", e); } }

boolean isValidJson(String s) { try { objectMapper.readTree(s); return true; } catch (Exception e) { return false; } }

try { serializer.serialize(eventInstance); } catch (FlowableIllegalArgumentException e) { LOG.error("invalid json payload: " + e.getCause()); throw e; }

When it happens

Trigger: Payload definition type is 'json' and the value is a String that is not valid JSON (malformed XML-ish text, truncated JSON, plain text).

Common situations: Producers sending hand-concatenated JSON; template output with unescaped characters; truncated payloads from message size limits; single-quoted pseudo-JSON strings.

Understand the failure class

Background: JSON parse error: "Unexpected token" / "not valid JSON" / "failed to parse" — what JSON parsers are really complaining about — this error's family across 45 libraries.

Related errors

• Cannot convert event payload ${jsonValue} to type 'json'
• Error writing app model to json
• Failed to parse jase
• Cannot convert event payload ${payloadInstanceValue} to type
• Cannot convert event payload ${payloadInstanceValue} to type

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/7e4d67bf457f57b5. Report an issue: GitHub.