org.axonframework.eventhandling

Class AbstractEventBus

java.lang.Object

org.axonframework.eventhandling.AbstractEventBus

All Implemented Interfaces:

EventBus, MessageDispatchInterceptorSupport<EventMessage<?>>, StreamableMessageSource<TrackedEventMessage<?>>, SubscribableMessageSource<EventMessage<?>>

Direct Known Subclasses:

AbstractEventStore, SimpleEventBus

public abstract class AbstractEventBus
extends Object
implements EventBus

Base class for the Event Bus. In case events are published while a Unit of Work is active the Unit of Work root coordinates the timing and order of the publication.

This implementation of the EventBus directly forwards all published events (in the callers' thread) to subscribed event processors. Event processors are expected to implement asynchronous handling themselves or alternatively open an event stream using EventBus.openStream(TrackingToken).

Since:

3.0

Author:

Allard Buijze, René de Waele

Constructor Summary

Constructors

Constructor and Description
AbstractEventBus() Initializes an event bus with a NoOpMessageMonitor.
AbstractEventBus(MessageMonitor<? super EventMessage<?>> messageMonitor) Initializes an event bus.

Method Summary

Modifier and Type	Method and Description
protected void	afterCommit(List<? extends EventMessage<?>> events) Process given events after the Unit of Work has been committed.
protected void	commit(List<? extends EventMessage<?>> events) Process given events while the Unit of Work root is being committed.
protected List<? extends EventMessage<?>>	intercept(List<? extends EventMessage<?>> events) Invokes all the dispatch interceptors.
protected void	prepareCommit(List<? extends EventMessage<?>> events) Process given events while the Unit of Work root is preparing for commit.
void	publish(List<? extends EventMessage<?>> events) Publish a collection of events on this bus (one, or multiple).
protected List<EventMessage<?>>	queuedMessages() Returns a list of all the events staged for publication in this Unit of Work.
Registration	registerDispatchInterceptor(MessageDispatchInterceptor<? super EventMessage<?>> dispatchInterceptor) Register the given interceptor with this bus.
Registration	subscribe(Consumer<List<? extends EventMessage<?>>> eventProcessor) Subscribe the given messageProcessor to this message source.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.axonframework.eventhandling.EventBus

openStream, publish

Methods inherited from interface org.axonframework.messaging.StreamableMessageSource

createHeadToken, createTailToken, createTokenAt, createTokenSince

Constructor Detail

AbstractEventBus

public AbstractEventBus()

Initializes an event bus with a NoOpMessageMonitor.

AbstractEventBus

public AbstractEventBus(MessageMonitor<? super EventMessage<?>> messageMonitor)

Initializes an event bus. Uses the given messageMonitor to report ingested messages and report the result of processing the message.

Parameters:

messageMonitor - The monitor used to monitor the ingested messages

Method Detail

subscribe

public Registration subscribe(Consumer<List<? extends EventMessage<?>>> eventProcessor)

Description copied from interface: SubscribableMessageSource

Subscribe the given messageProcessor to this message source. When subscribed, it will receive all messages published to this source.

If the given messageProcessor is already subscribed, nothing happens.

Specified by:

subscribe in interface SubscribableMessageSource<EventMessage<?>>

Parameters:

eventProcessor - The message processor to subscribe

Returns:

a handle to unsubscribe the messageProcessor. When unsubscribed it will no longer receive messages.

registerDispatchInterceptor

public Registration registerDispatchInterceptor(MessageDispatchInterceptor<? super EventMessage<?>> dispatchInterceptor)

Register the given interceptor with this bus. When subscribed it will intercept any event messages published on this bus.

If the given interceptor is already registered, nothing happens.

In case a Unit of Work is active, the preprocessor is not invoked by this Event Bus until the Unit of Work root is committed.

Specified by:

registerDispatchInterceptor in interface EventBus

Specified by:

registerDispatchInterceptor in interface MessageDispatchInterceptorSupport<EventMessage<?>>

Parameters:

dispatchInterceptor -

Returns:

a handle to unregister the dispatchInterceptor. When unregistered it will no longer be given event messages published on this bus.

publish

public void publish(List<? extends EventMessage<?>> events)

Description copied from interface: EventBus

Publish a collection of events on this bus (one, or multiple). The events will be dispatched to all subscribed listeners.

Implementations may treat the given events as a single batch and distribute the events as such to all subscribed EventListeners.

Specified by:

publish in interface EventBus

Parameters:

events - The collection of events to publish

queuedMessages

protected List<EventMessage<?>> queuedMessages()

Returns a list of all the events staged for publication in this Unit of Work. Changing this list will not affect the publication of events.

Returns:

a list of all the events staged for publication

intercept

protected List<? extends EventMessage<?>> intercept(List<? extends EventMessage<?>> events)

Invokes all the dispatch interceptors.

Parameters:

events - The original events being published

Returns:

The events to actually publish

prepareCommit

protected void prepareCommit(List<? extends EventMessage<?>> events)

Process given events while the Unit of Work root is preparing for commit. The default implementation signals the registered MessageMonitor that the given events are ingested and passes the events to each registered event processor.

Parameters:

events - Events to be published by this Event Bus

commit

protected void commit(List<? extends EventMessage<?>> events)

Process given events while the Unit of Work root is being committed. The default implementation does nothing.

Parameters:

events - Events to be published by this Event Bus

afterCommit

protected void afterCommit(List<? extends EventMessage<?>> events)

Process given events after the Unit of Work has been committed. The default implementation does nothing.

Parameters:

events - Events to be published by this Event Bus