Package org.axonframework.modelling.entity.child

Class AbstractEntityChildMetamodel<C,P>

java.lang.Object

org.axonframework.modelling.entity.child.AbstractEntityChildMetamodel<C,P>

Type Parameters:

C - the type of the child entity

P - the type of the parent entity

All Implemented Interfaces:

EntityChildMetamodel<C,P>, EntityEvolver<P>

Direct Known Subclasses:

ListEntityChildMetamodel, MapEntityChildMetamodel, SingleEntityChildMetamodel

@Internal
public abstract class AbstractEntityChildMetamodel<C,P>
extends Object
implements EntityChildMetamodel<C,P>

Abstract EntityChildMetamodel that implements common functionality for most implementations.

It defines how to handle commands and events for a child entity. The implementor is responsible for defining how to resolve the child entities from the parent, keyed by an implementation-specific identity (getChildEntities(Object)), and how to apply the evolved child entities to the parent (applyEvolvedChildEntities(Object, Map)).

The keys returned by getChildEntities(Object) are opaque to this class; they only exist so that evolve(Object, EventMessage, ProcessingContext) can preserve the association between a child entity and its identity when a child is evolved or removed, regardless of whether the parent stores its children in a List (keyed by index), as a single field (keyed by a constant), or in a Map (keyed by the map's own keys).

Since:

5.0.0

Author:

Mitchell Herrijgers, Steven van Beelen

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
protected static class	AbstractEntityChildMetamodel.Builder<C,P,R extends AbstractEntityChildMetamodel.Builder<C,P,R>>

Field Summary

Fields

Modifier and Type	Field	Description
protected final CommandTargetResolver<C>	commandTargetResolver
protected final EventTargetMatcher<C>	eventTargetMatcher
protected final EntityMetamodel<C>	metamodel

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	AbstractEntityChildMetamodel(EntityMetamodel<C> metamodel, CommandTargetResolver<C> commandTargetResolver, EventTargetMatcher<C> eventTargetMatcher)

Method Summary

Modifier and Type	Method	Description
protected abstract P	applyEvolvedChildEntities(P entity, Map<Object,C> evolvedChildEntities)	Applies the evolved child entities, keyed by the same implementation-specific identity returned by getChildEntities(Object), to the given entity.
boolean	canHandle(CommandMessage message, P parentEntity, ProcessingContext context)	Checks if this child can handle the given CommandMessage for the given parent entity, and a child entity is available to handle it.
Class<C>	entityType()	Returns the Class of the child entity this metamodel describes.
P	evolve(P entity, EventMessage event, ProcessingContext context)	Evolve the given entity by applying the given event to it.
protected abstract Map<Object,C>	getChildEntities(P parent)	Resolves the child entities of the given parent, keyed by an implementation-specific identity.
MessageStream.Single<CommandResultMessage>	handle(CommandMessage message, P parentEntity, ProcessingContext context)	Handles the given CommandMessage for the given child entity, using the provided parent entity.
Set<QualifiedName>	supportedCommands()	Returns the set of all QualifiedNames that this metamodel supports for command handlers.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.axonframework.modelling.entity.child.EntityChildMetamodel

entityMetamodel

Field Details

metamodel

protected final EntityMetamodel<C> metamodel

commandTargetResolver

protected final CommandTargetResolver<C> commandTargetResolver

eventTargetMatcher

protected final EventTargetMatcher<C> eventTargetMatcher

Constructor Details

AbstractEntityChildMetamodel

protected AbstractEntityChildMetamodel(EntityMetamodel<C> metamodel,
 CommandTargetResolver<C> commandTargetResolver,
 EventTargetMatcher<C> eventTargetMatcher)

Method Details

supportedCommands

public Set<QualifiedName> supportedCommands()

Description copied from interface: EntityChildMetamodel

Returns the set of all QualifiedNames that this metamodel supports for command handlers.

Specified by:

supportedCommands in interface EntityChildMetamodel<C,P>

Returns:

a set of QualifiedName instances representing the supported command names

canHandle

public boolean canHandle(CommandMessage message,
 P parentEntity,
 ProcessingContext context)

Description copied from interface: EntityChildMetamodel

Checks if this child can handle the given CommandMessage for the given parent entity, and a child entity is available to handle it.

Specified by:

canHandle in interface EntityChildMetamodel<C,P>

Parameters:

message - the CommandMessage to check

parentEntity - the parent entity instance to check against

context - the ProcessingContext for the command

Returns:

true if this child can handle the command, false otherwise

handle

public MessageStream.Single<CommandResultMessage> handle(CommandMessage message,
 P parentEntity,
 ProcessingContext context)

Description copied from interface: EntityChildMetamodel

Handles the given CommandMessage for the given child entity, using the provided parent entity.

Specified by:

handle in interface EntityChildMetamodel<C,P>

Parameters:

message - the CommandMessage to handle

parentEntity - the child entity instance to handle the command for

context - the ProcessingContext for the command

Returns:

the result of the command handling, which may be a CommandResultMessage or an error message

evolve

public P evolve(P entity,
 EventMessage event,
 ProcessingContext context)

Description copied from interface: EntityEvolver

Evolve the given entity by applying the given event to it.

Specified by:

evolve in interface EntityEvolver<C>

Parameters:

entity - The current entity to evolve with the given event.

event - The event that might adjust the entity.

context - The context within which to evolve the entity by the given event.

Returns:

The evolved entity based on the given event, or the same entity when nothing happened.

getChildEntities

protected abstract Map<Object,C> getChildEntities(P parent)

Resolves the child entities of the given parent, keyed by an implementation-specific identity.

The returned immutable Map must preserve iteration order (e.g. LinkedHashMap), as that order determines the order in which candidates are offered to the CommandTargetResolver and EventTargetMatcher.

Parameters:

parent - the parent entity to resolve the child entities from

Returns:

the child entities of the given parent, keyed by an implementation-specific identity

applyEvolvedChildEntities

protected abstract P applyEvolvedChildEntities(P entity,
 Map<Object,C> evolvedChildEntities)

Applies the evolved child entities, keyed by the same implementation-specific identity returned by getChildEntities(Object), to the given entity. A key that was present in getChildEntities(Object) but is absent from evolvedChildEntities indicates that the corresponding child entity was evolved to null and should be removed.

Parameters:

entity - the parent entity to apply the evolved child entities to

evolvedChildEntities - the evolved child entities, keyed by the same identity as getChildEntities(Object)

Returns:

the evolved parent entity

entityType

public Class<C> entityType()

Description copied from interface: EntityChildMetamodel

Returns the Class of the child entity this metamodel describes.

Specified by:

entityType in interface EntityChildMetamodel<C,P>

Returns:

the Class of the child entity this metamodel describes