Handler (eventsourced-aggregates 0.9.15 API)

Type Parameters:

COMMAND - The type of Commands that the handle(Object, Object) can process

EVENT - The type of Events that can be returned by handle(Object, Object) and applied in the StateEvolver.applyEvent(Object, Object)

ERROR - The type of Error that can be returned by the handle(Object, Object) method

STATE - The type of Aggregate State that this Decider works with in handle(Object, Object), InitialStateProvider.initialState(), StateEvolver.applyEvent(Object, Object) and IsStateFinalResolver.isFinal(Object)

All Known Subinterfaces:

Decider<COMMAND,EVENT,ERROR,STATE>

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 Handler<COMMAND,EVENT,ERROR,STATE>
```
Decider related interface that is responsible for handling COMMAND(s),whose side effect is either an ERROR or a List of EVENT's (can be an empty list)

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`HandlerResult<ERROR,EVENT>`	`handle(COMMAND cmd, STATE state)`	The `execute` method is responsible for handling a `COMMAND`, which can either result in an `ERROR` or a list of `EVENT`'s (can be an empty list). Note: This method is called `decide` in the decider pattern Idempotent handling of a `COMMAND` will result in an empty list of `EVENT`'s

- Method Detail
  - handle
```
HandlerResult<ERROR,EVENT> handle(COMMAND cmd,
                                        STATE state)
```
    The execute method is responsible for handling a COMMAND, which can either result in an ERROR or a list of EVENT's (can be an empty list).
    Note: This method is called decide in the decider pattern
    Idempotent handling of a COMMAND will result in an empty list of EVENT's
    
    Parameters:
    
    cmd - the command to handle
    
    state - the state of the aggregate
    
    Returns:
    
    either an ERROR or a list of EVENT's.
    Idempotent handling of a COMMAND will result in an empty list of EVENT's