pekko/akka-docs/rst/java/code/docs/extension/ExtensionDocTest.java

/**
 * Copyright (C) 2009-2017 Lightbend Inc. <http://www.lightbend.com>
 */
package docs.extension;

//#imports
import akka.actor.*;
import java.util.concurrent.atomic.AtomicLong;

//#imports

import docs.AbstractJavaTest;
import org.junit.Test;

public class ExtensionDocTest extends AbstractJavaTest {

  static
  //#extension
  public class CountExtensionImpl implements Extension {
    //Since this Extension is a shared instance
    // per ActorSystem we need to be threadsafe
    private final AtomicLong counter = new AtomicLong(0);

    //This is the operation this Extension provides
    public long increment() {
      return counter.incrementAndGet();
    }
  }

  //#extension

  static
  //#extensionid
  public class CountExtension extends AbstractExtensionId<CountExtensionImpl>
    implements ExtensionIdProvider {
    //This will be the identifier of our CountExtension
    public final static CountExtension CountExtensionProvider = new CountExtension();

    private CountExtension() {}

    //The lookup method is required by ExtensionIdProvider,
    // so we return ourselves here, this allows us
    // to configure our extension to be loaded when
    // the ActorSystem starts up
    public CountExtension lookup() {
      return CountExtension.CountExtensionProvider; //The public static final
    }

    //This method will be called by Akka
    // to instantiate our Extension
    public CountExtensionImpl createExtension(ExtendedActorSystem system) {
      return new CountExtensionImpl();
    }
  }

  //#extensionid

  static
  //#extension-usage-actor
  public class MyActor extends AbstractActor {
    @Override
    public Receive createReceive() {
      return receiveBuilder()
        .matchAny(msg -> {
          // typically you would use static import of the
          // CountExtension.CountExtensionProvider field
          CountExtension.CountExtensionProvider.get(getContext().system()).increment();
        })
        .build();
    }
  }

  //#extension-usage-actor

  @Test
  public void demonstrateHowToCreateAndUseAnAkkaExtensionInJava() {
    final ActorSystem system = null;
    try {
      //#extension-usage
      // typically you would use static import of the
      // CountExtension.CountExtensionProvider field
      CountExtension.CountExtensionProvider.get(system).increment();
      //#extension-usage
    } catch (Exception e) {
      //do nothing
    }
  }

}