Package org.axonframework.messaging.eventhandling.sequencing

Class SequentialPolicy

java.lang.Object

org.axonframework.messaging.eventhandling.sequencing.SequentialPolicy

All Implemented Interfaces:

SequencingPolicy

public class SequentialPolicy
extends Object
implements SequencingPolicy

SequencingPolicy that requires sequential handling of all events delivered to an event handler.

Since:

0.3

Author:

Allard Buijze

Field Summary

Fields

Modifier and Type	Field	Description
static final Object	FULL_SEQUENTIAL_POLICY	Object used to represent the full sequential policy.
static final SequentialPolicy	INSTANCE	Singleton instance of the SequentialPolicy.

Method Summary

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

Methods inherited from class java.lang.Object

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

Field Details

INSTANCE

public static final SequentialPolicy INSTANCE

Singleton instance of the SequentialPolicy.

FULL_SEQUENTIAL_POLICY

@Internal
public static final Object FULL_SEQUENTIAL_POLICY

Object used to represent the full sequential policy.

Method Details

getSequenceIdentifierFor

public Optional<Object> getSequenceIdentifierFor(@Nonnull
 EventMessage task,
 @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:

task - 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.