Package org.axonframework.messaging.eventhandling.sequencing

Class SequentialPerAggregatePolicy

java.lang.Object

org.axonframework.messaging.eventhandling.sequencing.SequentialPerAggregatePolicy

All Implemented Interfaces:

SequencingPolicy

public class SequentialPerAggregatePolicy
extends Object
implements SequencingPolicy

Concurrency policy that requires sequential processing of events raised by the same aggregate. Events from different aggregates may be processed in different threads.

Since:

0.3.0

Author:

Allard Buijze

Constructor Summary

Constructors

Constructor	Description
SequentialPerAggregatePolicy()

Method Summary

Modifier and Type	Method	Description
Optional<Object>	getSequenceIdentifierFor(EventMessage event, ProcessingContext context)	Returns the sequence identifier for the given event.
static SequentialPerAggregatePolicy	instance()	Return a singleton instance of the SequentialPerAggregatePolicy.

Methods inherited from class java.lang.Object

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

Constructor Details

SequentialPerAggregatePolicy

public SequentialPerAggregatePolicy()

Method Details

instance

public static SequentialPerAggregatePolicy instance()

Return a singleton instance of the SequentialPerAggregatePolicy.

Returns:

A singleton SequentialPerAggregatePolicy.

getSequenceIdentifierFor

public Optional<Object> getSequenceIdentifierFor(@Nonnull
 EventMessage event,
 @Nonnull
 ProcessingContext context)

Description copied from interface: SequencingPolicy

Returns the sequence identifier for the given event. When two events have the same identifier (as defined by their equals method), they will be executed sequentially. A Optional#empty() value indicates that there are no sequencing requirements for the handling of this event.

The Optional#empty() should ONLY be returned when the policy cannot determine a sequence identifier for the given event. This typically happens when the policy is not applicable for the specific event type. When Optional#empty() is returned, it is up to the component using this policy to provide a default behavior, use another policy, or throw an exception / react in any other way - as appropriate.

Specified by:

getSequenceIdentifierFor in interface SequencingPolicy

Parameters:

event - The event for which to get the sequencing identifier.

context - The processing context in which the event is being handled. This instance of the ProcessingContext doesn't allow you to register phases actions by for example ProcessingLifecycle.on(org.axonframework.messaging.core.unitofwork.ProcessingLifecycle.Phase, java.util.function.Function<org.axonframework.messaging.core.unitofwork.ProcessingContext, java.util.concurrent.CompletableFuture<?>>) or retrieving components by ApplicationContext.component(java.lang.Class<C>).

Returns:

A sequence identifier for the given event, or Optional#empty() if this policy cannot determine a sequence identifier for the given event.