Package org.axonframework.eventsourcing

Class AggregateSnapshotter

java.lang.Object

org.axonframework.eventsourcing.AbstractSnapshotter

org.axonframework.eventsourcing.AggregateSnapshotter

All Implemented Interfaces:

Snapshotter

Direct Known Subclasses:

SpringAggregateSnapshotter

public class AggregateSnapshotter
extends AbstractSnapshotter

Implementation of a snapshotter that uses the actual aggregate and its state to create a snapshot event. The motivation is that an aggregate always contains all relevant state. Therefore, storing the aggregate itself inside an event should capture all necessary information.

Since:

0.6

Author:

Allard Buijze

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	AggregateSnapshotter.Builder	Builder class to instantiate a AggregateSnapshotter.

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	AggregateSnapshotter(AggregateSnapshotter.Builder builder)	Instantiate a AggregateSnapshotter based on the fields contained in the AggregateSnapshotter.Builder.

Method Summary

Modifier and Type	Method	Description
static AggregateSnapshotter.Builder	builder()	Instantiate a Builder to be able to create a AggregateSnapshotter.
protected DomainEventMessage	createSnapshot(Class<?> aggregateType, String aggregateIdentifier, DomainEventStream eventStream)	Creates a snapshot event for an aggregate of which passed events are available in the given eventStream.
protected AggregateFactory<?>	getAggregateFactory(Class<?> aggregateType)	Returns the AggregateFactory registered for the given aggregateType, or null if no such AggregateFactory is known.
protected void	registerAggregateFactory(AggregateFactory<?> aggregateFactory)	Registers the given aggregateFactory with this snapshotter.

Methods inherited from class org.axonframework.eventsourcing.AbstractSnapshotter

createSnapshotterTask, getEventStore, getExecutor, scheduleSnapshot

Methods inherited from class java.lang.Object

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

Constructor Details

AggregateSnapshotter

protected AggregateSnapshotter(AggregateSnapshotter.Builder builder)

Instantiate a AggregateSnapshotter based on the fields contained in the AggregateSnapshotter.Builder.

Will assert that the EventStore, ParameterResolverFactory and HandlerDefinition are not null, and will throw an AxonConfigurationException if any of them is null. The SpanFactory is defaulted to a NoOpSpanFactory.

Parameters:

builder - the AggregateSnapshotter.Builder used to instantiate a AggregateSnapshotter instance

Method Details

builder

public static AggregateSnapshotter.Builder builder()

Instantiate a Builder to be able to create a AggregateSnapshotter.

The Executor is defaulted to an DirectExecutor.INSTANCE and the TransactionManager defaults to a NoTransactionManager. Additionally, this Builder has convenience functions to default the ParameterResolverFactory and HandlerDefinition based on instances of these available on the classpath in case these are not provided (respectively AggregateSnapshotter.Builder.buildParameterResolverFactory() and AggregateSnapshotter.Builder.buildHandlerDefinition()). Upon instantiation of a AggregateSnapshotter, it is recommended to use these function to set those fields.

The EventStore is a hard requirement and as such should be provided.

Returns:

a Builder to be able to create a AggregateSnapshotter

See Also:

• ClasspathParameterResolverFactory
• ClasspathHandlerDefinition

createSnapshot

protected DomainEventMessage createSnapshot(Class<?> aggregateType,
 String aggregateIdentifier,
 DomainEventStream eventStream)

Description copied from class: AbstractSnapshotter

Creates a snapshot event for an aggregate of which passed events are available in the given eventStream. May return null to indicate a snapshot event is not necessary or appropriate for the given event stream.

Specified by:

createSnapshot in class AbstractSnapshotter

Parameters:

aggregateType - The aggregate's type identifier

aggregateIdentifier - The identifier of the aggregate to create a snapshot for

eventStream - The event stream containing the aggregate's past events

Returns:

the snapshot event for the given events, or null if none should be stored.

getAggregateFactory

protected AggregateFactory<?> getAggregateFactory(Class<?> aggregateType)

Returns the AggregateFactory registered for the given aggregateType, or null if no such AggregateFactory is known.

Subclasses may override this method to enhance how AggregateFactories are retrieved. They may choose to registerAggregateFactory(AggregateFactory) if it hasn't been found using this implementation.

Parameters:

aggregateType - The type to get the AggregateFactory for

Returns:

the appropriate AggregateFactory, or null if not found

registerAggregateFactory

protected void registerAggregateFactory(AggregateFactory<?> aggregateFactory)

Registers the given aggregateFactory with this snapshotter. If a factory for this type was already registered, it is overwritten with this one.

Parameters:

aggregateFactory - the AggregateFactory to register