A Java actor library for parallel execution. Modernize common concurrency patterns with JavaActors, a lightweight Java actor library.
JavaActors is built around three core interfaces:
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Message is a message sent between actors. Message is a container for three (optional) values and some behavior:
- source is the sending actor.
- subject is a string defining the meaning of the message (also known as a command).
- data is any parameter data for the message; often a map, list, or array. Parameters can be data to process and/or other actors to interact with.
- subjectMatches() checks to see if the message subject matches a string or regular expression.
The default message class for the JavaActors package is DefaultMessage.
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ActorManager is a manager of actors. It is responsible for allocating threads (and thus processors) to actors to process messages. ActorManager has the following key behaviors or characteristics:
- createActor() creates an actor and associates it with this manager.
- startActor() starts an actor.
- detachActor() stops an actor and disassociates it from this manager.
- send()/broadcast() sends a message to an actor, a set of actors, any actor for a category, or all actors.
In most programs, there is a single ActorManager, although multiple are allowed if you want to manage multiple thread and/or actor pools. The default implementation of this interface is DefaultActorManager.
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Actor is a unit of execution that processes messages one at a time. Actors have the following key behaviors or characteristics:
- Each actor has a name, which must be unique per ActorManager.
- Each actor belongs to a category; categories are a means to send messages to one member of a group of actors. An actor can belong to only one category at a time.
- receive() is called whenever the ActorManager can provide a thread to execute the actor on. It is called only when a message for the actor exists. To be most effective, an actor should process messages quickly and not enter long waits (such as for human input).
- willReceive() allows the actor to filter potential message subjects.
- peek() allows the actor and others to see if there are pending messages, possibly for select subjects.
- remove() allows the actor and others to remove or cancel any yet unprocessed messages.
- getMessageCount() allows the actor and others to get the number of pending messages.
- getMaxMessageCount() allows the actor to limit how many pending messages are supported; this method can be used to prevent runaway sends.
Most programs have many actors, often of different types. Actors can be created at the start of a program or created (and destroyed) as a program executes. The actor package in this article includes an abstract class called AbstractActor, on which actor implementations are based.
Original Author:
Barry Feigenbaum, software engineer currently (30 May 2012) working at Dell and previously at IBM and Amazon. He is a Sun (now Oracle) Certified Java Programmer, Developer and Architect. Barry has authored several other developerWorks articles and presented at conferences such as JavaOne, as well as authoring several technical books. He holds a Ph.D. in Computer Engineering.
Original Source:
http://www.ibm.com/developerworks/java/library/j-javaactors/
Original License:
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