Package org.axonframework.messaging.core.sequencing

Class SequentialPerAggregatePolicy

java.lang.Object

org.axonframework.messaging.core.sequencing.SequentialPerAggregatePolicy

All Implemented Interfaces:

SequencingPolicy<EventMessage>

public class SequentialPerAggregatePolicy
extends Object
implements SequencingPolicy<EventMessage>

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

This policy only applies for event messages.

Since:

0.3.0

Author:

Allard Buijze

Field Summary

Fields

Modifier and Type	Field	Description
static final SequentialPerAggregatePolicy	INSTANCE	Singleton instance of the SequentialPerAggregatePolicy.

Constructor Summary

Constructors

Constructor	Description
SequentialPerAggregatePolicy()

Method Summary

Modifier and Type	Method	Description
Optional<Object>	sequenceIdentifierFor(EventMessage message, ProcessingContext context)	Returns the sequence identifier for the given message.

Methods inherited from class java.lang.Object

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

Field Details

INSTANCE

public static final SequentialPerAggregatePolicy INSTANCE

Singleton instance of the SequentialPerAggregatePolicy.

Constructor Details

SequentialPerAggregatePolicy

public SequentialPerAggregatePolicy()

Method Details

sequenceIdentifierFor

public Optional<Object> sequenceIdentifierFor(EventMessage message,
 ProcessingContext context)

Description copied from interface: SequencingPolicy

Returns the sequence identifier for the given message. When two messages 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 message.

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

Specified by:

sequenceIdentifierFor in interface SequencingPolicy<EventMessage>

Parameters:

message - the message for which to get the sequencing identifier.

context - the processing context in which the message is being handled. There might be limitations to the instance of the ProcessingContext depending on where the SequencingPolicy is being applied. When handling Events for example, 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 message, or Optional#empty() if this policy cannot determine a sequence identifier for the given message.