Akka/Scala example source code file (FactorialBackend.java)

This example Akka source code file (FactorialBackend.java) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Akka and Scala source code examples by using tags.

All credit for the original source code belongs to akka.io; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Akka tags/keywords

actor, akka, biginteger, callable, cluster, concurrent, dispatch, factorial, factorialbackend, factorialresult, future, integer, mapper, override, untypedactor

The FactorialBackend.java Akka example source code

package sample.cluster.factorial;

import java.math.BigInteger;
import java.util.concurrent.Callable;
import scala.concurrent.Future;
import akka.actor.UntypedActor;
import akka.dispatch.Mapper;
import static akka.dispatch.Futures.future;
import static akka.pattern.Patterns.pipe;

//#backend
public class FactorialBackend extends UntypedActor {

  @Override
  public void onReceive(Object message) {
    if (message instanceof Integer) {
      final Integer n = (Integer) message;
      Future<BigInteger> f = future(new Callable<BigInteger>() {
        public BigInteger call() {
          return factorial(n);
        }
      }, getContext().dispatcher());

      Future<FactorialResult> result = f.map(
          new Mapper<BigInteger, FactorialResult>() {
            public FactorialResult apply(BigInteger factorial) {
              return new FactorialResult(n, factorial);
            }
          }, getContext().dispatcher());

      pipe(result, getContext().dispatcher()).to(getSender());

    } else {
      unhandled(message);
    }
  }

  BigInteger factorial(int n) {
    BigInteger acc = BigInteger.ONE;
    for (int i = 1; i <= n; ++i) {
      acc = acc.multiply(BigInteger.valueOf(i));
    }
    return acc;
  }
}
//#backend