Documentation Version: 3.3-EA - Publication Date : May 22, 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;
import com.hazelcast.config.Config;

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

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

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

    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.