=doc #3689 Make activator template for akka.Main

akka-samples/akka-sample-main-java/LICENSE

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+Copyright 2013 Typesafe, Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.

akka-samples/akka-sample-main-java/activator.properties

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+name=akka-sample-main-java
+title=Akka Main in Java
+description=Actor based version of obligatory Hello World program using the generic launcher class akka.Main. 
+tags=Basics,akka,java,java,starter

akka-samples/akka-sample-main-java/build.sbt

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+name := "akka-sample-main-java"
+
+version := "1.0"
+
+scalaVersion := "2.10.3"
+
+libraryDependencies ++= Seq(
+  "com.typesafe.akka" %% "akka-actor" % "2.3-SNAPSHOT"
+)
+

akka-samples/akka-sample-main-java/project/build.properties

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+sbt.version=0.13.0

akka-samples/akka-sample-main-java/src/main/java/sample/hello/Greeter.java

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+/**
+ * Copyright (C) 2009-2013 Typesafe Inc. <http://www.typesafe.com>
+ */
+package sample.hello;
+
+import akka.actor.UntypedActor;
+
+public class Greeter extends UntypedActor {
+
+  public static enum Msg {
+    GREET, DONE;
+  }
+
+  @Override
+  public void onReceive(Object msg) {
+    if (msg == Msg.GREET) {
+      System.out.println("Hello World!");
+      getSender().tell(Msg.DONE, getSelf());
+    } else
+      unhandled(msg);
+  }
+
+}

akka-samples/akka-sample-main-java/src/main/java/sample/hello/HelloWorld.java

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+/**
+ * Copyright (C) 2009-2013 Typesafe Inc. <http://www.typesafe.com>
+ */
+
+package sample.hello;
+
+import akka.actor.Props;
+import akka.actor.UntypedActor;
+import akka.actor.ActorRef;
+
+public class HelloWorld extends UntypedActor {
+
+  @Override
+  public void preStart() {
+    // create the greeter actor
+    final ActorRef greeter = getContext().actorOf(Props.create(Greeter.class), "greeter");
+    // tell it to perform the greeting
+    greeter.tell(Greeter.Msg.GREET, getSelf());
+  }
+
+  @Override
+  public void onReceive(Object msg) {
+    if (msg == Greeter.Msg.DONE) {
+      // when the greeter is done, stop this actor and with it the application
+      getContext().stop(getSelf());
+    } else
+      unhandled(msg);
+  }
+}

akka-samples/akka-sample-main-java/src/main/java/sample/hello/Main.java

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+/**
+ *  Copyright (C) 2009-2013 Typesafe Inc. <http://www.typesafe.com>
+ */
+package sample.hello;
+
+public class Main {
+
+  public static void main(String[] args) {
+    akka.Main.main(new String[] { HelloWorld.class.getName() });
+  }
+}

akka-samples/akka-sample-main-java/src/main/java/sample/hello/Main2.java

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+/**
+ *  Copyright (C) 2009-2013 Typesafe Inc. <http://www.typesafe.com>
+ */
+package sample.hello;
+
+import akka.actor.ActorRef;
+import akka.actor.ActorSystem;
+import akka.actor.Props;
+import akka.actor.Terminated;
+import akka.actor.UntypedActor;
+import akka.event.Logging;
+import akka.event.LoggingAdapter;
+
+public class Main2 {
+
+  public static void main(String[] args) {
+    ActorSystem system = ActorSystem.create("Hello");
+    ActorRef a = system.actorOf(Props.create(HelloWorld.class), "helloWorld");
+    system.actorOf(Props.create(Terminator.class, a), "terminator");
+  }
+
+  public static class Terminator extends UntypedActor {
+
+    private final LoggingAdapter log = Logging.getLogger(getContext().system(), this);
+    private final ActorRef ref;
+
+    public Terminator(ActorRef ref) {
+      this.ref = ref;
+      getContext().watch(ref);
+    }
+
+    @Override
+    public void onReceive(Object msg) {
+      if (msg instanceof Terminated) {
+        log.info("{} has terminated, shutting down system", ref.path());
+        getContext().system().shutdown();
+      } else {
+        unhandled(msg);
+      }
+    }
+
+  }
+}

akka-samples/akka-sample-main-java/tutorial/index.html

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+<!-- <html> -->
+<head>
+    <title>The Obligatory Hello World</title>
+</head>
+
+<body>
+
+<div>
+<h2>The Obligatory Hello World</h2>
+
+<p>
+Since every programming paradigm needs to solve the tough problem of printing a
+well-known greeting to the console we’ll introduce you to the actor-based
+version.
+</p>
+
+<p>
+Open <a href="#code/src/main/java/sample/hello/HelloWorld.java" class="shortcut">HelloWorld.java</a>  
+</p>
+
+<p>
+The <code>HelloWorld</code> actor is the application’s “main” class; when it terminates
+the application will shut down—more on that later. The main business logic
+happens in the <code>preStart</code> method, where a <code>Greeter</code> actor is created
+and instructed to issue that greeting we crave for. When the greeter is done it
+will tell us so by sending back a message, and when that message has been
+received it will be passed into the behavior described by the <code>receive</code>
+method where we can conclude the demonstration by stopping the <code>HelloWorld</code>
+actor. 
+</p>
+
+</div>
+<div>
+
+<h2>The Greeter</h2>
+
+<p>
+You will be very curious to see how the <code>Greeter</code> actor performs the
+actual task. Open <a href="#code/src/main/java/sample/hello/Greeter.java" class="shortcut">Greeter.java</a>.
+</p>
+
+<p>
+
+This is extremely simple now: after its creation this actor will not do
+anything until someone sends it a message, and if that happens to be an
+invitation to greet the world then the <code>Greeter</code> complies and informs the
+requester that the deed has been done.
+</p>
+
+</div>
+<div>
+
+<h2>Main class</h2>
+
+<p>
+Go to the <a href="#run" class="shortcut">Run</a> tab, and start the application main class
+<code>sample.hello.Main</code>. In the log output you can see the "Hello World!" greeting.
+</p>
+
+<p>
+<a href="#code/src/main/java/sample/hello/Main.java" class="shortcut">Main.java</a>
+is actually just a small wrapper around the generic launcher class <code>akka.Main</code>,
+which expects only one argument: the class name of the application’s main actor. This main 
+method will then create the infrastructure needed for running the actors, start the
+given main actor and arrange for the whole application to shut down once the
+main actor terminates. Thus you will be able to run the application with a
+command similar to the following:
+</p>
+
+<pre><code>
+java -classpath <all those JARs> akka.Main sample.hello.HelloWorld
+</code></pre>
+
+<p>
+This conveniently assumes placement of the above class definitions in package
+<code>sample.hello</code> and it further assumes that you have the required JAR files for
+<code>scala-library</code>, <code>typesafe-config</code> and <code>akka-actor</code> available.
+The easiest would be to manage these dependencies with a 
+<a href="http://doc.akka.io/docs/akka/2.3-SNAPSHOT/intro/getting-started.html#Using_a_build_tool" target="_blank">build tool</a>.
+</p>
+
+<p>
+If you need more control of the startup code than what is provided by <code>akka.Main</code>
+you can easily write your own main class such as 
+<a href="#code/src/main/java/sample/hello/Main2.java" class="shortcut">Main2.java</a>
+</p>
+
+<p>
+Try to run the <code>sample.hello.Main2</code> class
+by selecting it in the 'Main class' menu in the <a href="#run" class="shortcut">Run</a> tab.
+</p> 
+  
+</div>
+
+</body>
+</html>