Package io.simplesource.api

Interface CommandHandler<K,​C,​E,​A>

  • Type Parameters:
    K - the aggregate key type
    C - all commands for this aggregate
    E - all events generated for this aggregate
    A - the aggregate type
    Functional Interface:
    This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.
    @FunctionalInterface
public interface CommandHandler<K,​C,​E,​A>
    A command handler is responsible for accepting or rejecting commands and turning accepted commands into a list of events by applying the appropriate business logic and validations based on the current state. To assist in determining if a command is valid, the command handler has an internal aggregator that parses events as they are generated. The internal aggregator is guaranteed to be fully up-to-date at the point a new command is interpreted with the latest aggregate provided as an argument ready to use for validation and business logic.

    • Method Summary

      Modifier and Type Method Description
      io.simplesource.data.Result<CommandError,​io.simplesource.data.NonEmptyList<E>> interpretCommand​(K key, A currentAggregate, C command)
      Determine whether you will accept the given command given the current aggregate and, if so, transform it into events.

    • Method Detail

      • interpretCommand

        io.simplesource.data.Result<CommandError,​io.simplesource.data.NonEmptyList<E>> interpretCommand​(K key,
                                                                                                      A currentAggregate,
                                                                                                      C command)
        Determine whether you will accept the given command given the current aggregate and, if so, transform it into events.
        Parameters:
        key - the aggregate key the command applies to
        currentAggregate - the aggregate for this aggregate guaranteed to be up to date with all events seen to date
        command - the command to validate and convert into events
        Returns:
        If rejecting, return a failed Result providing one or more Reasons for the rejection. If accepting, return one or more events that represent the command.