Package org.axonframework.modelling.command

Class AggregateAnnotationCommandHandler<T>

java.lang.Object

org.axonframework.modelling.command.AggregateAnnotationCommandHandler<T>

Type Parameters:

T - the type of aggregate this handler handles commands for

All Implemented Interfaces:

CommandMessageHandler, MessageHandler<CommandMessage<?>>

public class AggregateAnnotationCommandHandler<T>
extends Object
implements CommandMessageHandler

Command handler that registers a set of CommandHandler based on annotations of an aggregate. Those annotations may appear on methods, in which case a specific aggregate instance needs to be targeted by the command, or on the constructor. The latter will create a new Aggregate instance, which is then stored in the repository.

Despite being an CommandMessageHandler it does not actually handle the commands. During registration to the CommandBus it registers the CommandMessageHandlers directly instead of itself so duplicate command handlers can be detected and handled correctly.

Since:

1.2

Author:

Allard Buijze

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	AggregateAnnotationCommandHandler.Builder<T>	Builder class to instantiate a AggregateAnnotationCommandHandler.

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	AggregateAnnotationCommandHandler(AggregateAnnotationCommandHandler.Builder<T> builder)	Instantiate a AggregateAnnotationCommandHandler based on the fields contained in the AggregateAnnotationCommandHandler.Builder.

Method Summary

Modifier and Type	Method	Description
static <T> AggregateAnnotationCommandHandler.Builder<T>	builder()	Instantiate a Builder to be able to create a AggregateAnnotationCommandHandler.
boolean	canHandle(CommandMessage<?> message)	Indicates whether this handler can handle the given message
Object	handle(CommandMessage<?> commandMessage)	Handles the given message.
protected Object	resolveReturnValue(CommandMessage<?> command, Aggregate<T> createdAggregate)	Resolves the value to return when the given command has created the given aggregate.
Registration	subscribe(CommandBus commandBus)	Subscribe this command handler to the given commandBus.
Set<String>	supportedCommandNames()	Returns the set of command names this handler supports.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.axonframework.messaging.MessageHandler

canHandleType, getTargetType

Constructor Details

AggregateAnnotationCommandHandler

protected AggregateAnnotationCommandHandler(AggregateAnnotationCommandHandler.Builder<T> builder)

Instantiate a AggregateAnnotationCommandHandler based on the fields contained in the AggregateAnnotationCommandHandler.Builder.

Will assert that the Repository and CommandTargetResolver are not null, and will throw an AxonConfigurationException if either of them is null. Next to that, the provided Builder's goal is to create an AggregateModel (describing the structure of a given aggregate). To instantiate this AggregateModel, either an AggregateModel can be provided directly or an aggregateType of type Class can be used. The latter will internally resolve to an AggregateModel. Thus, either the AggregateModel or the aggregateType should be provided. An AxonConfigurationException is thrown if this criteria is not met.

Parameters:

builder - the AggregateAnnotationCommandHandler.Builder used to instantiate a AggregateAnnotationCommandHandler instance

Method Details

builder

public static <T>
AggregateAnnotationCommandHandler.Builder<T> builder()

Instantiate a Builder to be able to create a AggregateAnnotationCommandHandler.

The CommandTargetResolver is defaulted to a AnnotationCommandTargetResolver. The Repository is a hard requirement and as such should be provided. Next to that, this Builder's goal is to provide an AggregateModel (describing the structure of a given aggregate). To instantiate this AggregateModel, either an AggregateModel can be provided directly or an aggregateType of type Class can be used. The latter will internally resolve to an AggregateModel. Thus, either the AggregateModel or the aggregateType should be provided.

Type Parameters:

T - the type of aggregate this AggregateAnnotationCommandHandler handles commands for

Returns:

a Builder to be able to create a AggregateAnnotationCommandHandler

subscribe

public Registration subscribe(CommandBus commandBus)

Subscribe this command handler to the given commandBus. The command handler will be subscribed for each of the supported commands.

Parameters:

commandBus - The command bus instance to subscribe to

Returns:

A handle that can be used to unsubscribe

handle

public Object handle(CommandMessage<?> commandMessage)
              throws Exception

Description copied from interface: MessageHandler

Handles the given message.

Specified by:

handle in interface MessageHandler<T>

Parameters:

commandMessage - The message to be processed.

Returns:

The result of the message processing.

Throws:

Exception - any exception that occurs during message handling

canHandle

public boolean canHandle(CommandMessage<?> message)

Description copied from interface: MessageHandler

Indicates whether this handler can handle the given message

Specified by:

canHandle in interface MessageHandler<T>

Parameters:

message - The message to verify

Returns:

true if this handler can handle the message, otherwise false

resolveReturnValue

protected Object resolveReturnValue(CommandMessage<?> command,
 Aggregate<T> createdAggregate)

Resolves the value to return when the given command has created the given aggregate. This implementation returns the identifier of the created aggregate.

This method may be overridden to change the return value of this Command Handler

Parameters:

command - The command being executed

createdAggregate - The aggregate that has been created as a result of the command

Returns:

The value to report as result of the command

supportedCommandNames

public Set<String> supportedCommandNames()

Description copied from interface: CommandMessageHandler

Returns the set of command names this handler supports.

Specified by:

supportedCommandNames in interface CommandMessageHandler

Returns:

the set of supported command names