akka.agent
Class Agent<T>

java.lang.Object
  extended by akka.agent.Agent<T>

public abstract class Agent<T>
extends java.lang.Object

The Agent class was inspired by agents in Clojure.

Agents provide asynchronous change of individual locations. Agents are bound to a single storage location for their lifetime, and only allow mutation of that location (to a new state) to occur as a result of an action. Update actions are functions that are asynchronously applied to the Agent's state and whose return value becomes the Agent's new state. The state of an Agent should be immutable.

While updates to Agents are asynchronous, the state of an Agent is always immediately available for reading by any thread (using ''get'' or ''apply'') without any messages.

Agents are reactive. The update actions of all Agents get interleaved amongst threads in a thread pool. At any point in time, at most one ''send'' action for each Agent is being executed. Actions dispatched to an agent from another thread will occur in the order they were sent, potentially interleaved with actions dispatched to the same agent from other sources.

Example of usage:


 val agent = Agent(5)

 agent send (_ * 2)

 ...

 val result = agent()
 // use result ...

 

Agent is also monadic, which means that you can compose operations using for-comprehensions. In monadic usage the original agents are not touched but new agents are created. So the old values (agents) are still available as-is. They are so-called 'persistent'.

Example of monadic usage:


 val agent1 = Agent(3)
 val agent2 = Agent(5)

 for (value <- agent1) {
   result = value + 1
 }

 val agent3 = for (value <- agent1) yield value + 1

 val agent4 = for {
   value1 <- agent1
   value2 <- agent2
 } yield value1 + value2

 

==DEPRECATED STM SUPPORT==

Agents participating in enclosing STM transaction is a deprecated feature in 2.3.

If an Agent is used within an enclosing transaction, then it will participate in that transaction. Agents are integrated with the STM - any dispatches made in a transaction are held until that transaction commits, and are discarded if it is retried or aborted.


Constructor Summary
Agent()
           
 
Method Summary
abstract  scala.concurrent.Future<T> alter(scala.Function1<T,T> f)
          Dispatch a function to update the internal state, and return a Future where that new state can be obtained.
abstract  scala.concurrent.Future<T> alter(T newValue)
          Dispatch an update to the internal state, and return a Future where that new state can be obtained.
abstract  scala.concurrent.Future<T> alterOff(scala.Function1<T,T> f, scala.concurrent.ExecutionContext ec)
          Dispatch a function to update the internal state but on its own thread, and return a Future where that new state can be obtained.
 T apply()
          Read the internal state of the agent.
static
<T> Agent<T>
create(T initialValue, scala.concurrent.ExecutionContext context)
          Java API: Factory method for creating an Agent.
abstract
<B> Agent<B>
flatMap(scala.Function1<T,Agent<B>> f)
          Flatmap this agent to a new agent, applying the function to the internal state.
abstract
<U> void
foreach(scala.Function1<T,U> f)
          Applies the function to the internal state.
abstract  scala.concurrent.Future<T> future()
          A future to the current value that will be completed after any currently queued updates.
abstract  T get()
          Java API: Read the internal state of the agent.
abstract
<B> Agent<B>
map(scala.Function1<T,B> f)
          Map this agent to a new agent, applying the function to the internal state.
abstract  void send(scala.Function1<T,T> f)
          Dispatch a function to update the internal state.
abstract  void send(T newValue)
          Dispatch a new value for the internal state.
abstract  void sendOff(scala.Function1<T,T> f, scala.concurrent.ExecutionContext ec)
          Dispatch a function to update the internal state but on its own thread.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

Agent

public Agent()
Method Detail

create

public static <T> Agent<T> create(T initialValue,
                                  scala.concurrent.ExecutionContext context)
Java API: Factory method for creating an Agent.


get

public abstract T get()
Java API: Read the internal state of the agent.


apply

public T apply()
Read the internal state of the agent.


send

public abstract void send(T newValue)
Dispatch a new value for the internal state. Behaves the same as sending a function (x => newValue).


send

public abstract void send(scala.Function1<T,T> f)
Dispatch a function to update the internal state. In Java, pass in an instance of akka.dispatch.Mapper.


sendOff

public abstract void sendOff(scala.Function1<T,T> f,
                             scala.concurrent.ExecutionContext ec)
Dispatch a function to update the internal state but on its own thread. This does not use the reactive thread pool and can be used for long-running or blocking operations. Dispatches using either sendOff or send will still be executed in order. In Java, pass in an instance of akka.dispatch.Mapper.


alter

public abstract scala.concurrent.Future<T> alter(T newValue)
Dispatch an update to the internal state, and return a Future where that new state can be obtained. In Java, pass in an instance of akka.dispatch.Mapper.


alter

public abstract scala.concurrent.Future<T> alter(scala.Function1<T,T> f)
Dispatch a function to update the internal state, and return a Future where that new state can be obtained. In Java, pass in an instance of akka.dispatch.Mapper.


alterOff

public abstract scala.concurrent.Future<T> alterOff(scala.Function1<T,T> f,
                                                    scala.concurrent.ExecutionContext ec)
Dispatch a function to update the internal state but on its own thread, and return a Future where that new state can be obtained. This does not use the reactive thread pool and can be used for long-running or blocking operations. Dispatches using either alterOff or alter will still be executed in order. In Java, pass in an instance of akka.dispatch.Mapper.


future

public abstract scala.concurrent.Future<T> future()
A future to the current value that will be completed after any currently queued updates.


map

public abstract <B> Agent<B> map(scala.Function1<T,B> f)
Map this agent to a new agent, applying the function to the internal state. Does not change the value of this agent. In Java, pass in an instance of akka.dispatch.Mapper.


flatMap

public abstract <B> Agent<B> flatMap(scala.Function1<T,Agent<B>> f)
Flatmap this agent to a new agent, applying the function to the internal state. Does not change the value of this agent. In Java, pass in an instance of akka.dispatch.Mapper.


foreach

public abstract <U> void foreach(scala.Function1<T,U> f)
Applies the function to the internal state. Does not change the value of this agent. In Java, pass in an instance of akka.dispatch.Foreach.