Package com.reallifedeveloper.common.domain.event

Class ThreadLocalDomainEventPublisher

java.lang.Object

com.reallifedeveloper.common.domain.event.ThreadLocalDomainEventPublisher

All Implemented Interfaces:

DomainEventPublisher

public class ThreadLocalDomainEventPublisher
extends Object
implements DomainEventPublisher

A publisher of domain events that keeps track of subscribers on a per-thread basis. It is assumed that subscription and publishing are done by the same thread, and publishing is handled synchronously. To handle events asynchronously, a subscriber could send a message to a message queue, or store the event for later processing.

If threads are reused, it is important to call the reset() method to clear any previous subscribers.

The normal use-case for this class is as follows:

• A request comes in to an application service.
• The application service creates or retrieves an instance of this class and calls the reset() method.
• The application service registers all necessary subscribers using the subscribe(DomainEventSubscriber) method.
• The application service delegates to domain services or aggregates, which publish events when something interesting happens in the domain, using the publish(DomainEvent) method.

Author:

RealLifeDeveloper

Constructor Summary

Constructors

Constructor	Description
ThreadLocalDomainEventPublisher()

Method Summary

Modifier and Type	Method	Description
void	publish(DomainEvent event)	Publishes a domain event, i.e., calls the DomainEventSubscriber.handleEvent(DomainEvent) method for each registered subscriber.
void	reset()	Removes all subscribers.
void	subscribe(DomainEventSubscriber<? extends DomainEvent> subscriber)	Registers an event handler with this publisher.

Methods inherited from class java.lang.Object

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

Constructor Details

ThreadLocalDomainEventPublisher

public ThreadLocalDomainEventPublisher()

Method Details

subscribe

public void subscribe(DomainEventSubscriber<? extends DomainEvent> subscriber)

Registers an event handler with this publisher.

Specified by:

subscribe in interface DomainEventPublisher

Parameters:

subscriber - the event handler to register

Throws:

IllegalStateException - if called while publishing events

publish

public void publish(DomainEvent event)

Publishes a domain event, i.e., calls the DomainEventSubscriber.handleEvent(DomainEvent) method for each registered subscriber.

Specified by:

publish in interface DomainEventPublisher

Parameters:

event - the domain event to publish

Throws:

IllegalStateException - if called while already publishing events

reset

public void reset()

Removes all subscribers. Since subscribers are stored on a per-thread basis, and since threads may be reused, this method should be called when starting to handle a new request.

Throws:

IllegalStateException - if called while publishing events