flowable/flowable-engine · error · FlowableIllegalStateException

No event defined for taskListener in UserTask '" +…

Error message

No event defined for taskListener in UserTask '" + userTask.getName() + "'. Line: " + listener.getXmlRowNumber()

What it means

When executing task listeners for a user task, ListenerNotificationHelper checks that each FlowableListener declares an event. If listener.getEvent() is null, it throws FlowableIllegalStateException, because without an event the listener can never be matched to a lifecycle moment.

Solutions

Add the event attribute to the taskListener element in the BPMN XML (event="create", "assignment", "complete", "delete", or "all")
If adding listeners in code, call .event(TaskListener.EVENTNAME_ALL_EVENTS) or a specific event on the listener builder
Validate the deployed XML against the flowable XSD before deployment to catch the missing attribute

Example fix

// before
<flowable:taskListener class="com.example.MyListener" />
// after
<flowable:taskListener event="create" class="com.example.MyListener" />

Defensive patterns

Strategy: validation

Validate before calling

for (FlowableListener l : userTask.getTaskListeners()) {
    if (l.getEvent() == null) throw new IllegalStateException("taskListener missing event attr in " + userTask.getId());
}

Type guard

boolean hasEvent(FlowableListener l) { return l.getEvent() != null; }

Try / catch

try {
    runtimeService.startProcessInstanceByKey("myProcess");
} catch (FlowableIllegalStateException e) {
    if (e.getMessage().startsWith("No event defined for taskListener")) {
        log.error("BPMN XML has taskListener without event attribute: {}", e.getMessage());
    }
}

Prevention

Always set event (or "all") on every taskListener element
Validate BPMN XML against the Flowable XSD before deployment
Use the Flowable Modeler which enforces the event attribute

When it happens

Trigger: A <flowable:taskListener> element in the BPMN XML is missing the required 'event' attribute (e.g. <flowable:taskListener class="..."/> with no event="create|assignment|complete|delete|all").

Common situations: Hand-edited or generated BPMN XML omitting the event attribute; modeler export dropping the attribute; listener added programmatically via builder without .event(...).

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/7f5a679bcd917281. Report an issue: GitHub.

Appendix: source

Thrown at modules/flowable-engine/src/main/java/org/flowable/engine/impl/bpmn/listener/ListenerNotificationHelper.java:119

        addTransactionListener(listener, new ExecuteExecutionListenerTransactionListener(executionListener, scope, 
                        CommandContextUtil.getProcessEngineConfiguration().getCommandExecutor()));
    }

    public void executeTaskListeners(TaskEntity taskEntity, String eventType) {
        if (taskEntity.getProcessDefinitionId() != null) {
            org.flowable.bpmn.model.Process process = ProcessDefinitionUtil.getProcess(taskEntity.getProcessDefinitionId());
            FlowElement flowElement = process.getFlowElement(taskEntity.getTaskDefinitionKey(), true);
            if (flowElement instanceof UserTask userTask) {
                executeTaskListeners(userTask, taskEntity, eventType);
            }
        }
    }

    public void executeTaskListeners(UserTask userTask, TaskEntity taskEntity, String eventType) {
        for (FlowableListener listener : userTask.getTaskListeners()) {
            String event = listener.getEvent();
            if (event == null) {
                throw new FlowableIllegalStateException(
                        "No event defined for taskListener in UserTask '" + userTask.getName() + "'. Line: " + listener.getXmlRowNumber());
            }
            if (event.equals(eventType) || event.equals(TaskListener.EVENTNAME_ALL_EVENTS)) {
                BaseTaskListener taskListener = createTaskListener(listener);

                if (listener.getOnTransaction() != null) {
                    ExecutionEntity executionEntity = CommandContextUtil.getExecutionEntityManager().findById(taskEntity.getExecutionId());
                    planTransactionDependentTaskListener(executionEntity, (TransactionDependentTaskListener) taskListener, listener);
                } else {
                    taskEntity.setEventName(eventType);
                    taskEntity.setEventHandlerId(listener.getId());
                    
                    try {
                        CommandContextUtil.getProcessEngineConfiguration().getDelegateInterceptor()
                                .handleInvocation(new TaskListenerInvocation((TaskListener) taskListener, taskEntity));
                    } finally {
                        taskEntity.setEventName(null);
                    }

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