Package org.axonframework.modelling.command

Class MetaDataCommandTargetResolver

java.lang.Object

org.axonframework.modelling.command.MetaDataCommandTargetResolver

All Implemented Interfaces:

CommandTargetResolver

public class MetaDataCommandTargetResolver
extends Object
implements CommandTargetResolver

CommandTargetResolver implementation that uses MetaData entries to extract the identifier and optionally the version of the aggregate that the command targets.

While this may require duplication of data (as the identifier is already included in the payload as well), it is a more performing alternative to a reflection based CommandTargetResolvers.

Since:

2.0

Author:

Allard Buijze

Constructor Summary

Constructors

Constructor	Description
MetaDataCommandTargetResolver(String identifierKey)	Initializes the MetaDataCommandTargetResolver to use the given identifierKey as the MetaData key to the aggregate identifier, and a null (ignored) version.
MetaDataCommandTargetResolver(String identifierKey, String versionKey)	Initializes the MetaDataCommandTargetResolver to use the given identifierKey as the MetaData key to the aggregate identifier, and the given versionKey as key to the (optional) version entry.

Method Summary

Modifier and Type	Method	Description
VersionedAggregateIdentifier	resolveTarget(CommandMessage<?> command)	Returns the Aggregate Identifier and optionally the expected version of the aggregate on which the given command should be executed.

Methods inherited from class java.lang.Object

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

Constructor Details

MetaDataCommandTargetResolver

public MetaDataCommandTargetResolver(String identifierKey)

Initializes the MetaDataCommandTargetResolver to use the given identifierKey as the MetaData key to the aggregate identifier, and a null (ignored) version.

When the given identifierKey is not present in a command's MetaData, resolveTarget(CommandMessage) will raise an IllegalArgumentException

Parameters:

identifierKey - The key of the metadata field containing the aggregate identifier

MetaDataCommandTargetResolver

public MetaDataCommandTargetResolver(String identifierKey,
 String versionKey)

Initializes the MetaDataCommandTargetResolver to use the given identifierKey as the MetaData key to the aggregate identifier, and the given versionKey as key to the (optional) version entry.

When the given identifierKey is not present in a command's MetaData, resolveTarget(CommandMessage) will raise an IllegalArgumentException

Parameters:

identifierKey - The key of the metadata field containing the aggregate identifier

versionKey - The key of the metadata field containing the expected aggregate version. A null value may be provided to ignore the version

Method Details

resolveTarget

public VersionedAggregateIdentifier resolveTarget(@Nonnull
 CommandMessage<?> command)

Description copied from interface: CommandTargetResolver

Returns the Aggregate Identifier and optionally the expected version of the aggregate on which the given command should be executed.

The version may be null if no specific version is required. Furthermore, the returned VersionedAggregateIdentifier may be null entirely when the given command is targeted towards a CreationPolicy annotated command handler that (optionally) constructs a new aggregate instance.

Specified by:

resolveTarget in interface CommandTargetResolver

Parameters:

command - The command from which to extract the identifier and version.

Returns:

A VersionedAggregateIdentifier instance reflecting the aggregate to execute the command on, or null when the command is targeted towards a CreationPolicy annotated command handler that constructs a new aggregate instance.

See Also:

• AggregateCreationPolicy.ALWAYS
• AggregateCreationPolicy.CREATE_IF_MISSING