Documentation Version: 3.4 - Publication Date : Dec 24, 2014

Execution Callback

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

Let's use the Fibonacci series to explain this. The example code below 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 );
    }
  }
}

The example code below 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();
  }
};

ExecutionCallback has the methods onResponse and onFailure. In the above code, onResponse is called upon a valid response and prints the calculation result, whereas onFailure is called upon a failure and prints the stacktrace.