Lightbend Activator

Akka FSM in Java with Lambdas

Activator will be EOL-ed on May 24, 2017.

We’re making it easier and simpler for developers to get started with Lightbend technologies. This unfortunately means that future releases of Play, Akka and Scala will no longer include Activator support, and Lightbend’s Activator server will be decommissioned by the end of 2017. Instead of supporting Activator to create and set up development projects, we'll be supporting standard Giter8 templates for sbt users and Maven archetypes for Maven users. So going forward,

To create new Lightbend projects

Instead of using the Activator command, make sure you have sbt 0.13.13 (or higher), and use the “sbt new” command, providing the name of the template. For example, “$ sbt new akka/hello-akka.g8”. You can find a list of templates here.

Also, as a convenience, the Lightbend Project Starter allows you to quickly create a variety of example projects that you just unzip and run.

To create new templates

If you want to create new templates, you can now do that in Giter8.

To migrate templates from Activator to Giter8

If you created Activator templates in the past, please consider migrating them to Giter8 with this simple process.

Akka FSM in Java with Lambdas

Akka Team
Source
September 30, 2016
akka java java8 sample

Illustrating how to implement a finite state machine in actors.

How to get "Akka FSM in Java with Lambdas" on your computer

There are several ways to get this template.

Option 1: Choose akka-sample-fsm-java-lambda in the Lightbend Activator UI.

Already have Lightbend Activator (get it here)? Launch the UI then search for akka-sample-fsm-java-lambda in the list of templates.

Option 2: Download the akka-sample-fsm-java-lambda project as a zip archive

If you haven't installed Activator, you can get the code by downloading the template bundle for akka-sample-fsm-java-lambda.

  1. Download the Template Bundle for "Akka FSM in Java with Lambdas"
  2. Extract the downloaded zip file to your system
  3. The bundle includes a small bootstrap script that can start Activator. To start Lightbend Activator's UI:

    In your File Explorer, navigate into the directory that the template was extracted to, right-click on the file named "activator.bat", then select "Open", and if prompted with a warning, click to continue:

    Or from a command line:

     C:\Users\typesafe\akka-sample-fsm-java-lambda> activator ui 
    This will start Lightbend Activator and open this template in your browser.

Option 3: Create a akka-sample-fsm-java-lambda project from the command line

If you have Lightbend Activator, use its command line mode to create a new project from this template. Type activator new PROJECTNAME akka-sample-fsm-java-lambda on the command line.

Option 4: View the template source

The creator of this template maintains it at https://github.com/akka/akka.

Option 5: Preview the tutorial below

We've included the text of this template's tutorial below, but it may work better if you view it inside Activator on your computer. Activator tutorials are often designed to be interactive.

Preview the tutorial

Finite State Machine in Actors

This sample is an adaptation of Dining Hakkers. It illustrates how state and behavior can be managed within an Actor with two different approaches; using become and using the AbstractFSM class.

Dining Hakkers with Become

Open DiningHakkersOnBecome.java.

It illustrates how current behavior can be replaced with context.become. Note that no var members are used, instead the state is encoded in the current behavior and its parameters.

Go to the Run tab, and start the application main class sample.become.DiningHakkersOnBecome. In the log output you can see the actions of the Hakker actors.

Read more about become in the documentation.

Dining Hakkers with FSM

Open DiningHakkersOnFsm.java.

It illustrates how the states and transitions can be defined with the akka.actor.AbstractFSM class.

Go to the Run tab, and start the application main class sample.fsm.DiningHakkersOnFsm. In the log output you can see the actions of the Hakker actors.

Read more about akka.actor.FSM in the documentation.