flowable/flowable-engine · error · ActivitiIllegalArgumentException

event is null

Error message

event is null

What it means

DispatchEventCommand dispatches a FlowableEvent through the engine's event dispatcher. Before dispatching, it validates that the event supplied to the command is not null; a null event would otherwise cause a NullPointerException deep inside the dispatcher, so an ActivitiIllegalArgumentException is thrown explicitly.

Solutions

1. Ensure the event passed to runtimeService.dispatchEvent() is non-null before calling it
2. Verify the event factory (e.g. FlowableEventBuilder) call used to create the event actually succeeded
3. Check that variables holding the event are initialized before the dispatch call
4. Wrap the dispatch call in a null check or Objects.requireNonNull with a clear message

Example fix

// before
runtimeService.dispatchEvent(event);
// after
if (event != null) {
    runtimeService.dispatchEvent(event);
} else {
    throw new IllegalArgumentException("Cannot dispatch: event is null");
}

if (event == null) { throw new IllegalArgumentException("event must not be null before dispatch"); }

boolean isDispatchable(ActivitiEvent e) { return e != null; }

try { runtimeService.dispatchEvent(event); } catch (ActivitiIllegalArgumentException e) { LOGGER.error("Null event passed to dispatch", e); }

When it happens

Trigger: Calling RuntimeService.dispatchEvent(event) (or DispatchEventCmd via the command API) with a null ActivitiEvent, e.g. a variable holding the event was never initialized or a builder/factory returned null.

Common situations: Custom event listeners or integration code that builds events conditionally and passes the result straight to dispatchEvent; refactors where an event-creation helper silently started returning null.

Related errors

• comment is null
• Deployment id is null
• executionId is null
• Invalid case definition id : null
• model is null

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/d08bcda338cca4ff. Report an issue: GitHub.

Appendix: source

Thrown at modules/flowable5-engine/src/main/java/org/activiti/engine/impl/cmd/DispatchEventCommand.java:38

import org.flowable.common.engine.impl.interceptor.EngineConfigurationConstants;

/**
 * Command that dispatches an event.
 * 
 * @author Frederik Heremans
 */
public class DispatchEventCommand implements Command<Void> {

    protected FlowableEvent event;

    public DispatchEventCommand(FlowableEvent event) {
        this.event = event;
    }

    @Override
    public Void execute(CommandContext commandContext) {
        if (event == null) {
            throw new ActivitiIllegalArgumentException("event is null");
        }

        if (commandContext.getEventDispatcher().isEnabled()) {
            commandContext.getEventDispatcher().dispatchEvent(event, EngineConfigurationConstants.KEY_PROCESS_ENGINE_CONFIG);
        } else {
            throw new ActivitiException("Message dispatcher is disabled, cannot dispatch event");
        }

        return null;
    }

}

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