Akka basic program not working

Question

I have just started learning AKKA and written a sample program from the book Learning AKKA but the program does not run and it does not produce any useful information for further debugging. I am pasting the code files below please take a look and provide

SetRequest.java

package com.akkademy.messages;

public class SetRequest {
    private  String key;
    private  String value;

    public  SetRequest(String key, String value) {
        this.key = key;
        this.value = value;
    }

    public String getKey() {
        return key;
    }

    public String getValue() {
        return value;
    }
}

AkkademyDB.java

package com.akkademy;

import akka.actor.AbstractActor;
import akka.event.Logging;
import akka.event.LoggingAdapter;
import akka.japi.pf.ReceiveBuilder;
import com.akkademy.messages.SetRequest;

import java.util.HashMap;
import java.util.Map;

public class AkkademyDB extends AbstractActor{

    protected final LoggingAdapter log  = Logging.getLogger(context().system(),this);
    protected final Map<String,Object> map = new HashMap<>();

    private AkkademyDB(){
        receive(ReceiveBuilder.match(SetRequest.class,message->{
            log.info("Received set request-key:{} value: {}",message.getKey(),message.getValue());
        }).matchAny(o->log.info("received unknown message {}",o)).build()
        );
    }


}

AkkademyDBTest.java

package com.akkademy;

import akka.actor.ActorSystem;
import akka.actor.Props;
import akka.testkit.TestActorRef;
import com.akkademy.messages.SetRequest;
import akka.actor.ActorRef;
import org.junit.Test;

import static junit.framework.Assert.assertEquals;


public class AkkademyDBTest {

    ActorSystem system =  ActorSystem.create();

    @Test
    public void itShouldPlaceKeyValueFromSetMessageIntoMap() {
        TestActorRef<AkkademyDB> actorRef = TestActorRef.create(system, Props.create(AkkademyDB.class));
        actorRef.tell(new SetRequest("key","value"),ActorRef.noSender());
        AkkademyDB akkademyDB = actorRef.underlyingActor();
        assertEquals(akkademyDB.map.get("key"),"value");


    }
}

build.sbt

name := """akkademy-db"""

version := "1.0"

scalaVersion := "2.11.1"

libraryDependencies ++= Seq(
  "com.typesafe.akka" % "akka-actor_2.11" % "2.3.6",
  "com.typesafe.akka" % "akka-testkit_2.11" % "2.5.6" % "test",
  "junit" % "junit" % "4.12" % "test",
  "com.novocode" % "junit-interface" % "0.10" % "test")

Error Message received when running the test file is

/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/bin/java -ea -Didea.test.cyclic.buffer.size=1048576 -Dfile.encoding=UTF-8 -classpath "/Applications/IntelliJ IDEA.app/Contents/lib/idea_rt.jar:/Applications/IntelliJ IDEA.app/Contents/plugins/junit/lib/junit-rt.jar:/Applications/IntelliJ IDEA.app/Contents/plugins/junit/lib/junit5-rt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/charsets.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/deploy.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/ext/cldrdata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/ext/dnsns.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/ext/jaccess.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/ext/jfxrt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/ext/localedata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/ext/nashorn.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/ext/sunec.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/ext/sunjce_provider.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/ext/sunpkcs11.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/ext/zipfs.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/javaws.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/jce.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/jfr.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/jfxswt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/jsse.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/management-agent.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/plugin.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/resources.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/rt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/lib/ant-javafx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/lib/dt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/lib/javafx-mx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/lib/jconsole.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/lib/packager.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/lib/sa-jdi.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/lib/tools.jar:/Users/madhurjain/akkademy-db/target/scala-2.11/test-classes:/Users/madhurjain/akkademy-db/target/scala-2.11/classes:/Users/madhurjain/.ivy2/cache/org.scala-lang/scala-library/jars/scala-library-2.11.2.jar:/Users/madhurjain/.ivy2/cache/com.typesafe.akka/akka-actor_2.11/jars/akka-actor_2.11-2.3.6.jar:/Users/madhurjain/.ivy2/cache/com.typesafe/config/bundles/config-1.2.1.jar:/Users/madhurjain/.ivy2/cache/org.scala-tools.testing/test-interface/jars/test-interface-0.5.jar:/Users/madhurjain/.ivy2/cache/junit/junit-dep/jars/junit-dep-4.10.jar:/Users/madhurjain/.ivy2/cache/com.novocode/junit-interface/jars/junit-interface-0.10.jar:/Users/madhurjain/.ivy2/cache/com.typesafe/config/bundles/config-1.3.1.jar:/Users/madhurjain/.ivy2/cache/com.typesafe.akka/akka-actor_2.11/jars/akka-actor_2.11-2.5.6.jar:/Users/madhurjain/.ivy2/cache/com.typesafe.akka/akka-testkit_2.11/jars/akka-testkit_2.11-2.5.6.jar:/Users/madhurjain/.ivy2/cache/org.scala-lang/scala-library/jars/scala-library-2.11.11.jar:/Users/madhurjain/.ivy2/cache/org.scala-lang.modules/scala-java8-compat_2.11/bundles/scala-java8-compat_2.11-0.7.0.jar:/Users/madhurjain/.ivy2/cache/junit/junit/jars/junit-4.12.jar:/Users/madhurjain/.ivy2/cache/org.hamcrest/hamcrest-core/jars/hamcrest-core-1.3.jar" com.intellij.rt.execution.junit.JUnitStarter -ideVersion5 -junit4 com.akkademy.AkkademyDBTest
[INFO] [10/25/2017 17:59:59.509] [main] [akka://default/user/$$a] Received set request-key:key value: value

junit.framework.AssertionFailedError: 
Expected :null
Actual   :value
 <Click to see difference>


    at junit.framework.Assert.fail(Assert.java:50)
    at junit.framework.Assert.failNotEquals(Assert.java:287)
    at junit.framework.Assert.assertEquals(Assert.java:67)
    at junit.framework.Assert.assertEquals(Assert.java:74)
    at com.akkademy.AkkademyDBTest.itShouldPlaceKeyValueFromSetMessageIntoMap(AkkademyDBTest.java:22)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:45)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:42)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:263)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:68)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:157)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
    at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)

Answer 1

When the AcademyDB actor receives a SetRequest message, it doesn't put the message's key and value in its internal map but simply logs the key and value. Your test fails because it inspects the actor's map for the key-value pair and finds nothing.

Change your actor to put the SetRequest message's key-value pair in its map:

public class AkkademyDB extends AbstractActor {
    protected final LoggingAdapter log = Logging.getLogger(getContext().getSystem(), this);
    protected final Map<String, Object> map = new HashMap<>();

    @Override
    public Receive createReceive() {
        return receiveBuilder()
            .match(SetRequest.class, message -> {
                log.info("Received set request-key:{} value: {}", message.getKey(), message.getValue());
                map.put(message.getKey(), message.getValue()); // <--- put in map
            })
            .matchAny(o -> log.info("received unknown message {}", o))
            .build();
    }
}

Also, adjust your build.sbt to consistently use version 2.5.6 of the Akka jars:

name := "akkademy-db"

version := "1.0"

scalaVersion := "2.11.11"

val akkaVersion = "2.5.6"

libraryDependencies ++= Seq(
  "com.typesafe.akka" %% "akka-actor" % akkaVersion,
  "com.typesafe.akka" %% "akka-testkit" % akkaVersion,
  "junit" % "junit" % "4.12" % "test",
  "com.novocode" % "junit-interface" % "0.10" % "test")