io.simplesource.saga.action.eventsourcing

Interface EventSourcingSpec.UndoFunction<A,K,C>

Enclosing class:

EventSourcingSpec<A,D,K,C>

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 static interface EventSourcingSpec.UndoFunction<A,K,C>

The UndoFunction functional interface.

Method Summary

Modifier and Type	Method and Description
Optional<A>	apply(K aggregateKey, C command) The UndoFunction is a mechanism to take the result of the async invocation and turning it into an undo action command.

Method Detail

apply

Optional<A> apply(K aggregateKey,
                  C command)

The UndoFunction is a mechanism to take the result of the async invocation and turning it into an undo action command. This action command is passed back to the saga coordinator, and if the saga fails, this undo function will be invoked.

The return value of type A must satisfy the following property:

Whatever value command tranforms the aggregate to, if one takes the result of the UndoFunction.apply, decode it, and then apply it to this new aggregate value, it should result in the original aggregate value being restored.

Note that the undo command of an event sourcing action processor must have the same action type.

Parameters:

aggregateKey - the aggregate key

command - the Simple Sourcing command

Returns:

an undo command as an A, or Optional.empty() if no undo function is to be generated