Package org.apache.pekko.actor.typed.javadsl

Class Behaviors

java.lang.Object
org.apache.pekko.actor.typed.javadsl.Behaviors
public class Behaviors extends Object
Factories for pekko.actor.typed.Behavior.

  • Constructor Details

    • Behaviors

      public Behaviors()

  • Method Details

    • setup

      public static <T> Behavior<T> setup(Function<ActorContext<T>,Behavior<T>> factory)
      setup is a factory for a behavior. Creation of the behavior instance is deferred until the actor is started, as opposed to receive(org.apache.pekko.japi.function.Function2<org.apache.pekko.actor.typed.javadsl.ActorContext<T>, T, org.apache.pekko.actor.typed.Behavior<T>>) that creates the behavior instance immediately before the actor is running. The factory function pass the ActorContext as parameter and that can for example be used for spawning child actors.

      setup is typically used as the outer most behavior when spawning an actor, but it can also be returned as the next behavior when processing a message or signal. In that case it will be started immediately after it is returned, i.e. next message will be processed by the started behavior.

    • withStash

      public static <T> Behavior<T> withStash(int capacity, Function<StashBuffer<T>,Behavior<T>> factory)
      Support for stashing messages to unstash at a later time.

    • same

      public static <T> Behavior<T> same()
      Return this behavior from message processing in order to advise the system to reuse the previous behavior. This is provided in order to avoid the allocation overhead of recreating the current behavior where that is not necessary.

    • unhandled

      public static <T> Behavior<T> unhandled()
      Return this behavior from message processing in order to advise the system to reuse the previous behavior, including the hint that the message has not been handled. This hint may be used by composite behaviors that delegate (partial) handling to other behaviors.

    • stopped

      public static <T> Behavior<T> stopped()
      Return this behavior from message processing to signal that this actor shall terminate voluntarily. If this actor has created child actors then these will be stopped as part of the shutdown procedure.

      The PostStop signal that results from stopping this actor will be passed to the current behavior. All other messages and signals will effectively be ignored.

    • stopped

      public static <T> Behavior<T> stopped(Effect postStop)
      Return this behavior from message processing to signal that this actor shall terminate voluntarily. If this actor has created child actors then these will be stopped as part of the shutdown procedure.

      The PostStop signal that results from stopping this actor will first be passed to the current behavior and then the provided postStop callback will be invoked. All other messages and signals will effectively be ignored.

      An example of when the callback can be useful compared to the PostStop signal if you want to send a reply to the message that initiated a graceful stop.

    • empty

      public static <T> Behavior<T> empty()
      A behavior that treats every incoming message as unhandled.

    • ignore

      public static <T> Behavior<T> ignore()
      A behavior that ignores every incoming message and returns &ldquo;same&rdquo;.

    • receive

      public static <T> Behavior<T> receive(Function2<ActorContext<T>,T,Behavior<T>> onMessage)
      Construct an actor behavior that can react to incoming messages but not to lifecycle signals. After spawning this actor from another actor (or as the guardian of an pekko.actor.typed.ActorSystem) it will be executed within an ActorContext that allows access to the system, spawning and watching other actors, etc.

      Compared to using AbstractBehavior this factory is a more functional style of defining the Behavior. Processing the next message results in a new behavior that can potentially be different from this one. State is maintained by returning a new behavior that holds the new immutable state.

    • receiveMessage

      public static <T> Behavior<T> receiveMessage(Function<T,Behavior<T>> onMessage)
      Simplified version of <T>receive(org.apache.pekko.japi.function.Function2<org.apache.pekko.actor.typed.javadsl.ActorContext<T>,T,org.apache.pekko.actor.typed.Behavior<T>>) with only a single argument - the message to be handled. Useful for when the context is already accessible by other means, like being wrapped in an <T>setup(org.apache.pekko.japi.function.Function<org.apache.pekko.actor.typed.javadsl.ActorContext<T>,org.apache.pekko.actor.typed.Behavior<T>>) or similar.

      Construct an actor behavior that can react to incoming messages but not to lifecycle signals. After spawning this actor from another actor (or as the guardian of an pekko.actor.typed.ActorSystem) it will be executed within an ActorContext that allows access to the system, spawning and watching other actors, etc.

      Compared to using AbstractBehavior this factory is a more functional style of defining the Behavior. Processing the next message results in a new behavior that can potentially be different from this one. State is maintained by returning a new behavior that holds the new immutable state.

    • receiveMessageWithSame

      public static <T> Behavior<T> receiveMessageWithSame(Procedure<T> onMessage)
      Simplified version of <T>receiveMessage(org.apache.pekko.japi.function.Function<T,org.apache.pekko.actor.typed.Behavior<T>>) with only a single argument - the message to be handled, but it doesn't produce a return value of next behavior. Useful for when the behavior doesn't want to change in runtime.

      Construct an actor behavior that can react to incoming messages but not to lifecycle signals. After spawning this actor from another actor (or as the guardian of an pekko.actor.typed.ActorSystem) it will be executed within an ActorContext that allows access to the system, spawning and watching other actors, etc.

      Compared to using AbstractBehavior this factory is a more functional style of defining the Behavior. Processing the next message will not result in different behavior than this one

      Since:
      1.1.0

    • receive

      public static <T> Behavior<T> receive(Function2<ActorContext<T>,T,Behavior<T>> onMessage, Function2<ActorContext<T>,Signal,Behavior<T>> onSignal)
      Construct an actor behavior that can react to both incoming messages and lifecycle signals. After spawning this actor from another actor (or as the guardian of an pekko.actor.typed.ActorSystem) it will be executed within an ActorContext that allows access to the system, spawning and watching other actors, etc.

      Compared to using AbstractBehavior this factory is a more functional style of defining the Behavior. Processing the next message results in a new behavior that can potentially be different from this one. State is maintained by returning a new behavior that holds the new immutable state.

    • receive

      public static <T> BehaviorBuilder<T> receive(Class<T> type)
      Constructs an actor behavior builder that can build a behavior that can react to both incoming messages and lifecycle signals.

      Compared to using AbstractBehavior this factory is a more functional style of defining the Behavior. Processing the next message results in a new behavior that can potentially be different from this one. State is maintained by returning a new behavior that holds the new immutable state.

      Parameters:
      type - the supertype of all messages accepted by this behavior
      Returns:
      the behavior builder

    • receiveSignal

      public static <T> Behavior<T> receiveSignal(Function2<ActorContext<T>,Signal,Behavior<T>> handler)
      Construct an actor behavior that can react to lifecycle signals only.

    • intercept

      public static <O, I> Behavior<O> intercept(Supplier<BehaviorInterceptor<O,I>> behaviorInterceptor, Behavior<I> behavior)
      Intercept messages and signals for a behavior by first passing them to a pekko.actor.typed.BehaviorInterceptor

      When a behavior returns a new behavior as a result of processing a signal or message and that behavior already contains the same interceptor (defined by the pekko.actor.typed.BehaviorInterceptor#isSame method) only the innermost interceptor is kept. This is to protect against stack overflow when recursively defining behaviors.

      The interceptor is created with a factory function in case it has state and should not be shared. If the interceptor has no state the same instance can be returned from the factory to avoid unnecessary object creation.

    • monitor

      public static <T> Behavior<T> monitor(Class<T> interceptMessageClass, ActorRef<T> monitor, Behavior<T> behavior)
      Behavior decorator that copies all received message to the designated monitor pekko.actor.typed.ActorRef before invoking the wrapped behavior. The wrapped behavior can evolve (i.e. return different behavior) without needing to be wrapped in a monitor call again.

      Parameters:
      interceptMessageClass - Ensures that the messages of this class or a subclass thereof will be sent to the monitor. Other message types (e.g. a private protocol) will bypass the interceptor and be continue to the inner behavior.
      monitor - The messages will also be sent to this ActorRef
      behavior - The inner behavior that is decorated

    • logMessages

      public static <T> Behavior<T> logMessages(Behavior<T> behavior)
      Behavior decorator that logs all messages to the pekko.actor.typed.Behavior using the provided pekko.actor.typed.LogOptions default configuration before invoking the wrapped behavior. To include an MDC context then first wrap logMessages with withMDC.

    • logMessages

      public static <T> Behavior<T> logMessages(LogOptions logOptions, Behavior<T> behavior)
      Behavior decorator that logs all messages to the pekko.actor.typed.Behavior using the provided pekko.actor.typed.LogOptions configuration before invoking the wrapped behavior. To include an MDC context then first wrap logMessages with withMDC.

    • supervise

      public static <T> Behaviors.Supervise<T> supervise(Behavior<T> wrapped)
      Wrap the given behavior such that it is restarted (i.e. reset to its initial state) whenever it throws an exception of the given class or a subclass thereof. Exceptions that are not subtypes of Thr will not be caught and thus lead to the termination of the actor.

      It is possible to specify different supervisor strategies, such as restart, resume, backoff.

      The SupervisorStrategy is only invoked for "non fatal" (see NonFatal) exceptions.

      Example: 

      
 final Behavior[DbCommand] dbConnector = ...

 final Behavior[DbCommand] dbRestarts =
    Behaviors.supervise(dbConnector)
      .onFailure(SupervisorStrategy.restart) // handle all NonFatal exceptions

 final Behavior[DbCommand] dbSpecificResumes =
    Behaviors.supervise(dbConnector)
      .onFailure[IndexOutOfBoundsException](SupervisorStrategy.resume) // resume for IndexOutOfBoundsException exceptions

    • transformMessages

      public static <Outer, Inner> Behavior<Outer> transformMessages(Class<Outer> interceptMessageClass, Behavior<Inner> behavior, Function<PFBuilder<Outer,Inner>,PFBuilder<Outer,Inner>> selector)
      Transform the incoming messages by placing a funnel in front of the wrapped Behavior: the supplied PartialFunction decides which message to pull in (those that it is defined at) and may transform the incoming message to place them into the wrapped Behavior&rsquo;s type hierarchy. Signals are not transformed.

      Example: 

      
   Behavior<String> s = Behaviors.receive((ctx, msg) -> {
      return Behaviors.same();
    });
   Behavior<Number> n = Behaviors.transformMessages(Number.class, s, pf ->
     pf
         .match(BigInteger.class, i -> "BigInteger(" + i + ")")
         .match(BigDecimal.class, d -> "BigDecimal(" + d + ")")
         // drop all other kinds of Number
       );

      Parameters:
      interceptMessageClass - Ensures that only messages of this class or a subclass thereof will be intercepted. Other message types (e.g. a private protocol) will bypass the interceptor and be continue to the inner behavior untouched.
      behavior - the behavior that will receive the selected messages
      selector - a partial function builder for describing the selection and transformation
      Returns:
      a behavior of the Outer type

    • withTimers

      public static <T> Behavior<T> withTimers(Function<TimerScheduler<T>,Behavior<T>> factory)
      Support for scheduled self messages in an actor. It takes care of the lifecycle of the timers such as cancelling them when the actor is restarted or stopped.

      See Also:

    • withMdc

      public static <T> Behavior<T> withMdc(Class<T> interceptMessageClass, Function<T,Map<String,String>> mdcForMessage, Behavior<T> behavior)
      Per message MDC (Mapped Diagnostic Context) logging.

      Parameters:
      interceptMessageClass - Ensures that only messages of this class or a subclass thereof will be intercepted. Other message types (e.g. a private protocol) will bypass the interceptor and be continue to the inner behavior untouched.
      mdcForMessage - Is invoked before each message is handled, allowing to setup MDC, MDC is cleared after each message processing by the inner behavior is done.
      behavior - The actual behavior handling the messages, the MDC is used for the log entries logged through ActorContext.log

    • withMdc

      public static <T> Behavior<T> withMdc(Class<T> interceptMessageClass, Map<String,String> staticMdc, Behavior<T> behavior)
      Static MDC (Mapped Diagnostic Context)

      Parameters:
      interceptMessageClass - Ensures that only messages of this class or a subclass thereof will be intercepted. Other message types (e.g. a private protocol) will bypass the interceptor and be continue to the inner behavior untouched.
      staticMdc - This MDC is setup in the logging context for every message
      behavior - The actual behavior handling the messages, the MDC is used for the log entries logged through ActorContext.log

    • withMdc

      public static <T> Behavior<T> withMdc(Class<T> interceptMessageClass, Map<String,String> staticMdc, Function<T,Map<String,String>> mdcForMessage, Behavior<T> behavior)
      Combination of static and per message MDC (Mapped Diagnostic Context).

      Each message will get the static MDC plus the MDC returned for the message. If the same key are in both the static and the per message MDC the per message one overwrites the static one in the resulting log entries.

      * The staticMdc or mdcForMessage may be empty.

      Parameters:
      interceptMessageClass - Ensures that only messages of this class or a subclass thereof will be intercepted. Other message types (e.g. a private protocol) will bypass the interceptor and be continue to the inner behavior untouched.
      staticMdc - A static MDC applied for each message
      mdcForMessage - Is invoked before each message is handled, allowing to setup MDC, MDC is cleared after each message processing by the inner behavior is done.
      behavior - The actual behavior handling the messages, the MDC is used for the log entries logged through ActorContext.log