Supported Parameters for annotated handlers

By default, @CommandHandler annotated methods allow the following parameter types:

  • The first parameter is the payload of the command message. It may also be of type Message or CommandMessage, if the @CommandHandler annotation explicitly defined the name of the command the handler can process.

    By default, a command name is the fully qualified class name of the command its payload.

  • Parameters annotated with @MetaDataValue will resolve to the metadata value with the key as indicated on the annotation. If required is false (default), null is passed when the metadata value is not present.

    If required is true, the resolver will not match and prevent the method from being invoked when the metadata value is not present.

  • Parameters of type MetaData will have the entire MetaData of a CommandMessage injected.

  • Parameters of type UnitOfWork get the current unit of work injected. This allows command handlers to register actions to be performed at specific stages of the Unit of Work, or gain access to the resources registered with it.

  • Parameters of type Message, or CommandMessage will get the complete message, with both the payload and the metadata.

    This is useful if a method needs several metadata fields, or other properties of the wrapping Message.