Package org.axonframework.modelling.entity

Interface PolymorphicEntityMetamodelBuilder<E>

Type Parameters:

E - The type of the polymorphic entity this metamodel represents.

All Superinterfaces:

EntityMetamodelBuilder<E>

public interface PolymorphicEntityMetamodelBuilder<E>
extends EntityMetamodelBuilder<E>

Builder for a polymorphic EntityMetamodel, where a parent entity can have multiple concrete child entities. Command handlers of concrete types take precedence over the parent entity's command handlers. Event handlers are invoked on both, with the super entity's event handlers being invoked first.

Since:

5.0.0

Author:

Mitchell Herrijgers

See Also:

• PolymorphicEntityMetamodel

Method Summary

Modifier and Type	Method	Description
PolymorphicEntityMetamodelBuilder<E>	addChild(EntityChildMetamodel<?,E> child)	Adds a EntityChildMetamodel to this metamodel.
PolymorphicEntityMetamodelBuilder<E>	addConcreteType(EntityMetamodel<? extends E> metamodel)	Adds a concrete type to this metamodel.
PolymorphicEntityMetamodelBuilder<E>	creationalCommandHandler(QualifiedName qualifiedName, CommandHandler messageHandler)	Adds a CommandHandler to this metamodel for the given QualifiedName that is in charge of creation of the entity.
PolymorphicEntityMetamodelBuilder<E>	entityEvolver(EntityEvolver<E> entityEvolver)	Adds a EntityEvolver to this metamodel.
PolymorphicEntityMetamodelBuilder<E>	instanceCommandHandler(QualifiedName qualifiedName, EntityCommandHandler<E> messageHandler)	Adds an EntityCommandHandler to this metamodel for the given QualifiedName.

Methods inherited from interface org.axonframework.modelling.entity.EntityMetamodelBuilder

build

Method Details

instanceCommandHandler

@Nonnull
PolymorphicEntityMetamodelBuilder<E> instanceCommandHandler(@Nonnull
 QualifiedName qualifiedName,
 @Nonnull
 EntityCommandHandler<E> messageHandler)

Description copied from interface: EntityMetamodelBuilder

Adds an EntityCommandHandler to this metamodel for the given QualifiedName. The command handler will be invoked when a command with the given QualifiedName is received by the metamodel.

The entity should not exist for this command handler to be invoked. A non-null initial state is considered to be an existing entity. As such, only register this command if the Repository.loadOrCreate(Object, ProcessingContext) will always return a non-null entity for the given qualifiedName when the entity is not yet created.

You can register the same QualifiedName for both instance and creational command handlers. See the EntityMetamodelBuilder class documentation for more information on how this works.

Specified by:

instanceCommandHandler in interface EntityMetamodelBuilder<E>

Parameters:

qualifiedName - The QualifiedName of the command this handler handles.

messageHandler - The EntityCommandHandler to handle the command.

Returns:

This builder for further configuration.

creationalCommandHandler

@Nonnull
PolymorphicEntityMetamodelBuilder<E> creationalCommandHandler(@Nonnull
 QualifiedName qualifiedName,
 @Nonnull
 CommandHandler messageHandler)

Description copied from interface: EntityMetamodelBuilder

Adds a CommandHandler to this metamodel for the given QualifiedName that is in charge of creation of the entity. The handler is expected to create the entity.

The entity needs to not exist for this command handler to be invoked. A null initial state is considered to be a non-existing entity. As such, only register this command if the Repository.load(Object, ProcessingContext) will always return a null entity for the given qualifiedName when the entity is not yet created.

You can register the same QualifiedName for both instance and creational command handlers. See the EntityMetamodelBuilder class documentation for more information on how this works.

Note: If this metamodel is added as a child to another entity metamodel and has a creational command handler, it will result in an exception as child entities cannot be created through a creational command handler.

Specified by:

creationalCommandHandler in interface EntityMetamodelBuilder<E>

Parameters:

qualifiedName - The QualifiedName of the command this handler handles.

messageHandler - The CommandHandler to handle the command.

Returns:

This builder for further configuration.

addChild

@Nonnull
PolymorphicEntityMetamodelBuilder<E> addChild(@Nonnull
 EntityChildMetamodel<?,E> child)

Description copied from interface: EntityMetamodelBuilder

Adds a EntityChildMetamodel to this metamodel. The child metamodel will be used to handle commands for the child entity. You can build a tree of entities by adding child metamodels to the parent metamodel. Children command handlers take precedence over the parent command handlers. Event handlers will be invoked on both the parent and child metamodels, but the child metamodels will be invoked first.

There are various types of children that can be added to an entity metamodel:

• Single instances: For a field with a single instance, use the EntityChildMetamodel.single(Class, EntityMetamodel).
• List instances: For a list, use the EntityChildMetamodel.list(Class, EntityMetamodel).

When multiple children that can handle the same command are present, the children will be filtered based on EntityChildMetamodel.canHandle(CommandMessage, Object, ProcessingContext), and thus only invoke the child with a matching entity. If no child can handle the command, an exception will be thrown. If after filtering, multiple children can handle the command, an exception will be thrown.

Specified by:

addChild in interface EntityMetamodelBuilder<E>

Parameters:

child - The EntityChildMetamodel to add.

Returns:

This builder for further configuration.

entityEvolver

@Nonnull
PolymorphicEntityMetamodelBuilder<E> entityEvolver(@Nullable
 EntityEvolver<E> entityEvolver)

Description copied from interface: EntityMetamodelBuilder

Adds a EntityEvolver to this metamodel. This evolver will be called upon applying an event to the entity. The evolver is responsible for evolving the entity state based on the event. Note that providing an evolver is optional. However, if no evolver is provided, the entity state can only be changed through command handlers.

Calling this method a second time will override the previously set evolver.

Specified by:

entityEvolver in interface EntityMetamodelBuilder<E>

Parameters:

entityEvolver - The EntityEvolver to use.

Returns:

This builder for further configuration.

addConcreteType

@Nonnull
PolymorphicEntityMetamodelBuilder<E> addConcreteType(@Nonnull
 EntityMetamodel<? extends E> metamodel)

Adds a concrete type to this metamodel. The concrete type must be a subclass of the parent entity type.

Parameters:

metamodel - The EntityMetamodel for the concrete type.

Returns:

This builder for further configuration.