akka.actor
Interface Stash

All Superinterfaces:

Actor, RequiresMessageQueue<DequeBasedMessageQueueSemantics>, UnrestrictedStash

All Known Subinterfaces:

Creators.ActWithStash

All Known Implementing Classes:

UntypedActorWithStash

public interface Stash
extends UnrestrictedStash, RequiresMessageQueue<DequeBasedMessageQueueSemantics>

The Stash trait enables an actor to temporarily stash away messages that can not or should not be handled using the actor's current behavior.

Example:

    class ActorWithProtocol extends Actor with Stash {
      def receive = {
        case "open" ⇒
          unstashAll()
          context.become({
            case "write" ⇒ // do writing...
            case "close" ⇒
              unstashAll()
              context.unbecome()
            case msg ⇒ stash()
          }, discardOld = false)
        case "done" ⇒ // done
        case msg    ⇒ stash()
      }
    }
  

Note that the Stash trait can only be used together with actors that have a deque-based mailbox. By default Stash based actors request a Deque based mailbox since the stash trait extends RequiresMessageQueue[DequeBasedMessageQueueSemantics]. You can override the default mailbox provided when DequeBasedMessageQueueSemantics are requested via config:

    akka.actor.mailbox.requirements {
      "akka.dispatch.BoundedDequeBasedMessageQueueSemantics" = your-custom-mailbox
    }
  

Alternatively, you can add your own requirement marker to the actor and configure a mailbox type to be used for your marker.

For a Stash that also enforces unboundedness of the deque see UnboundedStash. For a Stash that does not enforce any mailbox type see UnrestrictedStash.

Note that the Stash trait must be mixed into (a subclass of) the Actor trait before any trait/class that overrides the preRestart callback. This means it's not possible to write Actor with MyActor with Stash if MyActor overrides preRestart.

Nested Class Summary

Nested classes/interfaces inherited from interface akka.actor.Actor

Actor.emptyBehavior$

Method Summary

akka.actor.ActorCell	actorCell()
int	capacity()
scala.collection.immutable.Vector<Envelope>	clearStash() INTERNAL API.
ActorContext	context() INTERNAL API.
void	enqueueFirst(Envelope envelope) Enqueues envelope at the first position in the mailbox.
DequeBasedMessageQueueSemantics	mailbox() INTERNAL API.
void	prepend(scala.collection.immutable.Seq<Envelope> others) Prepends others to this stash.
ActorRef	self() INTERNAL API.
void	stash() Adds the current message (the message that the actor received last) to the actor's stash.
scala.collection.immutable.Vector<Envelope>	theStash()
void	unstash() Prepends the oldest message in the stash to the mailbox, and then removes that message from the stash.
void	unstashAll() Prepends all messages in the stash to the mailbox, and then clears the stash.
void	unstashAll(scala.Function1<java.lang.Object,java.lang.Object> filterPredicate) INTERNAL API.

Methods inherited from interface akka.actor.UnrestrictedStash

postStop, preRestart

Methods inherited from interface akka.actor.Actor

aroundPostRestart, aroundPostStop, aroundPreRestart, aroundPreStart, aroundReceive, context, noSender, postRestart, preStart, receive, self, sender, supervisorStrategy, unhandled

Method Detail

context

ActorContext context()

INTERNAL API.

Context of the actor that uses this stash.

self

ActorRef self()

INTERNAL API.

Self reference of the actor that uses this stash.

theStash

scala.collection.immutable.Vector<Envelope> theStash()

actorCell

akka.actor.ActorCell actorCell()

capacity

int capacity()

mailbox

DequeBasedMessageQueueSemantics mailbox()

INTERNAL API.

The actor's deque-based message queue. mailbox.queue is the underlying Deque.

stash

void stash()

Adds the current message (the message that the actor received last) to the actor's stash.

Throws:

StashOverflowException - in case of a stash capacity violation

java.lang.IllegalStateException - if the same message is stashed more than once

prepend

void prepend(scala.collection.immutable.Seq<Envelope> others)

Prepends others to this stash. This method is optimized for a large stash and small others.

unstash

void unstash()

Prepends the oldest message in the stash to the mailbox, and then removes that message from the stash.

Messages from the stash are enqueued to the mailbox until the capacity of the mailbox (if any) has been reached. In case a bounded mailbox overflows, a MessageQueueAppendFailedException is thrown.

The unstashed message is guaranteed to be removed from the stash regardless if the unstash() call successfully returns or throws an exception.

unstashAll

void unstashAll()

Prepends all messages in the stash to the mailbox, and then clears the stash.

Messages from the stash are enqueued to the mailbox until the capacity of the mailbox (if any) has been reached. In case a bounded mailbox overflows, a MessageQueueAppendFailedException is thrown.

The stash is guaranteed to be empty after calling unstashAll().

unstashAll

void unstashAll(scala.Function1<java.lang.Object,java.lang.Object> filterPredicate)

INTERNAL API.

Prepends selected messages in the stash, applying filterPredicate, to the mailbox, and then clears the stash.

Messages from the stash are enqueued to the mailbox until the capacity of the mailbox (if any) has been reached. In case a bounded mailbox overflows, a MessageQueueAppendFailedException is thrown.

The stash is guaranteed to be empty after calling unstashAll(Any => Boolean).

Parameters:

filterPredicate - only stashed messages selected by this predicate are prepended to the mailbox.

clearStash

scala.collection.immutable.Vector<Envelope> clearStash()

INTERNAL API.

Clears the stash and and returns all envelopes that have not been unstashed.

enqueueFirst

void enqueueFirst(Envelope envelope)

Enqueues envelope at the first position in the mailbox. If the message contained in the envelope is a Terminated message, it will be ensured that it can be re-received by the actor.