Package groovy.concurrent

Interface StatefulHandler<S,T>

Type Parameters:

S - the state type

T - the message 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 StatefulHandler<S,T>

Context-aware handler for stateful actors. Receives the actor context, the current state, and the incoming message; returns the new state, which is also bound to the reply for Actor.sendAndGet(T) callers.

To stop the actor from inside the handler, call ctx.self().stop().

Known limitation around behaviour swaps. If a handler calls ctx.become(...) with a StatefulHandler whose S type is incompatible with the actor's current state, the ClassCastException surfaces on the next dispatch — not at the become call site. The actor's S is erased at construction and cannot be re-checked at the swap site; see ActorContext.become(StatefulHandler) for the full discussion.

Since:

6.0.0

See Also:

• Actor.stateful(Object, StatefulHandler)

Method Summary

Modifier and Type	Method	Description
S	apply(ActorContext<T> ctx, S state, T message)	Processes a single message and returns the new state.

Method Details

apply

S apply(ActorContext<T> ctx,
 S state,
 T message)

Processes a single message and returns the new state.

Parameters:

ctx - the actor context

state - the current state

message - the incoming message

Returns:

the new state