Documentation Version: 3.3 - Publication Date : Sep 07, 2014

Execution Callback

ExecutionCallback offered by Hazelcast allows you to asynchronously get notified when the execution is done.

Let's use the Fibonacci series to explain this. Below sample code is the calculation.

public class Fibonacci<Long> implements Callable<Long>, Serializable {
  int input = 0;

  public Fibonacci() {
  }

  public Fibonacci( int input ) {
    this.input = input;
  }

  public Long call() {
    return calculate( input );
  }

  private long calculate( int n ) {
    if (n <= 1) {
      return n;
    } else {
      return calculate( n - 1 ) + calculate( n - 2 );
    }
  }
}

And, below sample code prints the result asynchronously.

import com.hazelcast.core.Hazelcast;
import com.hazelcast.core.ExecutionCallback;
import com.hazelcast.core.IExecutorService;
import java.util.concurrent.Future;

HazelcastInstance hazelcastInstance = Hazelcast.newHazelcastInstance();
IExecutorService es = hazelcastInstance.getExecutorService();
Callable<Long> task = new Fibonacci( 10 );

es.submit(task, new ExecutionCallback<Long> () {

  @Override
  public void onResponse( Long response ) {
    System.out.println( "Fibonacci calculation result = " + response );
  }

  @Override
  public void onFailure( Throwable t ) {
    t.printStackTrace();
  }
};

As it can be seen, ExecutionCallback has the methods onResponse and onFailure. The former one in the above code is called upon a valid response and prints the calculation result, whereas the latter one is called upon a failure and prints the stacktrace.