README.md

Book Akka Essentials ⬆

Directory akka-essentials\ contains Akka code examples from Gupta's book Akka Essentials (Packt, 2012). It also includes different build scripts for experimenting with Akka on a Windows machine.

The code examples presented below are written both in Java and in Scala and can be built/run with the following tools:

Build tool	Build file	Parent file	Environment(s)
ant.bat	build.xml	build.xml	Any a)
gradle.bat	build.gradle	common.gradle	Any
make.exe b)	Makefile	Makefile.inc	Any
mvn.cmd	pom.xml	pom.xml	Any
sbt.bat	build.sbt		Any
cmd.exe	build.bat		Windows only

^a) Here "Any" means "tested on Windows, Cygwin, MSYS2 and UNIX".
^b) Default shell is /bin/sh as described in the online document Choosing the Shell.
 

FirstAkkaApplication Example

Code example FirstAkkaApplication¹ is an Akka application written in Java (e.g. MapReduceApplication.java, MasterActor.java²).

Batch file build.bat matches what the user would run from the command prompt (use option -debug to see the execution details):

> build -verbose run
Compile 9 Java source files to directory "target\classes"
[MapReduceApp-akka.actor.default-dispatcher-4] INFO akka.event.slf4j.Slf4jLogger - Slf4jLogger started
{over=1, quick=1, belong=1, lazy=1, best=1, man's=1, brown=1, fox=2, fell=1, tried=1, same=1, friend=1, family=1, dog=4, jump=1}

Commands ant.bat (build.xml), gradle.bat (build.gradle), make (Makefile), mvn (pom.xml) and sbt (build.sbt) produce the same output; for instance :

> make -s run
{over=1, quick=1, belong=1, lazy=1, best=1, man's=1, brown=1, fox=2, fell=1, tried=1, same=1, friend=1, family=1, dog=4, jump=1}

🔎 FirstAkkaApplicationScala is the same Akka application written in Scala (e.g. MapReduceApplication.scala, MasterActor.scala). For instance build.bat generates the following output:  

> build run
[MapReduceApp-akka.actor.default-dispatcher-4] INFO akka.event.slf4j.Slf4jLogger - Slf4jLogger started
HashMap(over -> 1, quick -> 1, belong -> 1, lazy -> 1, best -> 1, man's -> 1, brown -> 1, fox -> 2, fell -> 1, tried -> 1, same -> 1, friend -> 1, family -> 1, dog -> 4, jump -> 1)

ProcessOrder Example ▴

Code example ProcessOrder is an Akka application written in Java (e.g. ProcessOrderApp.java, ProcessOrderActor.java).

Batch file build.bat matches what the user would run from the command prompt (use option -debug to see the execution details):

> build -verbose run
Compile 8 Java source files to directory "target\classes"
[ProcessOrder-akka.actor.default-dispatcher-5] INFO akka.event.slf4j.Slf4jLogger - Slf4jLogger started
OrderActor: userId=1
OrderAggregate: akka.actor.Status$Failure

🔎 Code example ProcessOrderScala is the same Akka application written in Scala (e.g. MapReduceApplication.scala, MasterActor.scala). For instance build.bat generates the following output :  

> build run
...

PingPong Example ▴

Code example PingPong is an Akka application written in Java (e.g. PingPongApp.java, PingPongActor.java).

Batch file build.bat matches what the user would run from the command prompt (use option -debug to see the execution details):

> build -verbose run
Compile 2 Java source files to directory "target\classes"
[PingPong-akka.actor.default-dispatcher-5] INFO akka.event.slf4j.Slf4jLogger - Slf4jLogger started
PING
PONG
PING
PONG
PING
PONG
PING
PONG
PING
PONG
PING

🔎 PingPongScala is the same Akka application written in Scala (e.g. MapReduceApplication.scala, PingPongActor.scala). For instance build.bat generates the following output :  

> build run
[PingPong-akka.actor.default-dispatcher-4] INFO akka.event.slf4j.Slf4jLogger - Slf4jLogger started
PING
PONG
PING
PONG
PING
PONG
PING
PONG
PING
PONG
PING

Footnotes ▴

[1] Source code updates ↩

We have updated several deprecated code in the original examples of Gupta's book:

Original source code	Updated source code a)
(≤2.5) akka.actor.UntypedActor	akka.actor.UntypedAbstractActor
(≤2.3) akka.routing.RoundRobinRouter	akka.routing.RoundRobinPool
akka.dispatch.Await	scala.concurrent.Awaitb)
akka.dispatch.Future	scala.concurrent.Futurec)
(≤2.4) _system.shutdown()	_system.terminate()

^a) Akka version 2.6.x
^b) Object Await is defined in file scala/concurrent/package.scala since Scala 2.10.
^c) Trait/object Future is defined in file scala/concurrent/Future.scala since Scala 2.10.

See the online documentation for further informations:

• Migration Guide 2.8.x to 2.9.x
• Migration Guide 2.7.x to 2.8.x
• Migration Guide 2.6.x to 2.7.x
• Migration Guide 2.5.x to 2.6.x
• Migration Guide 2.4.x to 2.5.x
• Migration Guide 2.3.x to 2.4.x

[2] FirstAkkaApplication: 2 versions ↩

We actually provide two versions of FirstAkkaApplication:

• in FirstAkkaApplication the 4 actors are defined as subclasses of UntypedAbstractActor and do overwrite method onReceive(Object message).

  public class MapActor extends UntypedAbstractActor {
      // ...
      @Override
      public void onReceive(Object message) throws Exception {
          if (message instanceof String) {
              // ...
          } else
              unhandled(message);
      }
  }
  

• in FirstAkkaApplication2 the 4 actors are defined as subclasses of akka.actor.AbstractActor and do implement method createReceive().

  public class MapActor extends AbstractActor {
      // ...
      public Receive createReceive() {
          return receiveBuilder()
              .match(String.class, word -> { /* ... */ })
              .matchAny(message -> { unhandled(message); })
              .build();
      }
  }
  

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mics/May 2024 ▲