org.axonframework.eventsourcing

Class AbstractAggregateFactory<T>

java.lang.Object

org.axonframework.eventsourcing.AbstractAggregateFactory<T>

Type Parameters:

T - The type of Aggregate created by this factory

All Implemented Interfaces:

AggregateFactory<T>

Direct Known Subclasses:

GenericAggregateFactory

public abstract class AbstractAggregateFactory<T>
extends Object
implements AggregateFactory<T>

Abstract AggregateFactory implementation that is aware of snapshot events. If an incoming event is not a snapshot event, creation is delegated to the subclass.

Since:

2.0

Author:

Allard Buijze

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AbstractAggregateFactory(Class<T> aggregateBaseType) Initialize an aggregateFactory for the given aggregateBaseType.

Method Summary

Modifier and Type	Method and Description
T	createAggregateRoot(String aggregateIdentifier, DomainEventMessage<?> firstEvent) Instantiate the aggregate root using the given aggregate identifier and first event.
protected abstract T	doCreateAggregate(String aggregateIdentifier, DomainEventMessage firstEvent) Create an uninitialized Aggregate instance with the given aggregateIdentifier.
Class<T>	getAggregateType() Returns the type of aggregate this factory creates.
protected T	postProcessInstance(T aggregate) Perform any processing that must be done on an aggregate instance that was reconstructed from a Snapshot Event.

Methods inherited from class java.lang.Object

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

Constructor Detail

AbstractAggregateFactory

protected AbstractAggregateFactory(Class<T> aggregateBaseType)

Initialize an aggregateFactory for the given aggregateBaseType. If a first event is and instance of this aggregateBaseType, it is recognised as a snapshot event. Otherwise, the subclass is asked to instantiate a new aggregate root instance based on the first event.

Parameters:

aggregateBaseType - The base type of the aggregate roots created by this instance.

Method Detail

createAggregateRoot

public final T createAggregateRoot(String aggregateIdentifier,
                                   DomainEventMessage<?> firstEvent)

Description copied from interface: AggregateFactory

Instantiate the aggregate root using the given aggregate identifier and first event. The first event of the event stream is passed to allow the factory to identify the actual implementation type of the aggregate to create. The first event can be either the event that created the aggregate or, when using event sourcing, a snapshot event. In either case, the event should be designed, such that these events contain enough information to deduct the actual aggregate type.

Specified by:

createAggregateRoot in interface AggregateFactory<T>

Parameters:

aggregateIdentifier - the aggregate identifier of the aggregate to instantiate

firstEvent - The first event in the event stream. This is either the event generated during creation of the aggregate, or a snapshot event

Returns:

an aggregate root ready for initialization using a DomainEventStream.

postProcessInstance

protected T postProcessInstance(T aggregate)

Perform any processing that must be done on an aggregate instance that was reconstructed from a Snapshot Event. Implementations may choose to modify the existing instance, or return a new instance.

This method can be safely overridden. This implementation does nothing.

Parameters:

aggregate - The aggregate to post-process.

Returns:

The aggregate to initialize with the Event Stream

doCreateAggregate

protected abstract T doCreateAggregate(String aggregateIdentifier,
                                       DomainEventMessage firstEvent)

Create an uninitialized Aggregate instance with the given aggregateIdentifier. The given firstEvent can be used to define the requirements of the aggregate to create.

The given firstEvent is never a snapshot event.

Parameters:

aggregateIdentifier - The identifier of the aggregate to create

firstEvent - The first event in the Event Stream of the Aggregate

Returns:

The aggregate instance to initialize with the Event Stream

getAggregateType

public Class<T> getAggregateType()

Description copied from interface: AggregateFactory

Returns the type of aggregate this factory creates. All instances created by this factory must be an instanceOf this type.

Specified by:

getAggregateType in interface AggregateFactory<T>

Returns:

The type of aggregate created by this factory