Running multiple threads in web application

I need to execute parallel tasks in a web application. Right now, I have a java class that implements a Callable, where DMI is an object that I use in a JSF bean.

The problem is that all Callable objects are running in the same thread, then only after a complete execution of all of them, the thread changes. I want to run every object on a different thread. What am I doing wrong?

Class Callable

 public class ModuloCallable implements Callable<DMI> {

    private final String NOME;
    private final String URL;

    public ModuloCallable(String nome, String url) {
        this.NOME = nome;
        this.URL = url;
    }

    @Override
    public DMI call() {

        try {   

                /* Some code here to generate a DMI object */

                System.out.println("Thread number: " + Thread.currentThread().getId());

                return dmi;

            }

        } catch (NullPointerException e) {                

            return null;

        }

        return null;

    }
}

JSF Bean

@Named(value = "dmiBean")
@RequestScoped
public class DmiBean {

private DMI geradorG1;
private DMI geradorG2;
private DMI geradorG3;

/**
 * Creates a new instance of DmiBean
 */
public DmiBean() {
}

@PostConstruct
public void buscar() {
        ExecutorService executor = Executors.newCachedThreadPool();
        ModuloCallable G1C = new ModuloCallable("n1", "url1") 
        ModuloCallable G2C = new ModuloCallable("n2","url2");
        ModuloCallable G3C = new ModuloCallable("n3","url3");
        geradorG1 = getFutureValue(G1C, executor);
        geradorG2 = getFutureValue(G2C, executor);
        geradorG3 = getFutureValue(G3C, executor);
        executor.shutdown();
    }
   public DMI getFutureValue(ModuloCallable mc, ExecutorService e) {
        Future<DMI> f = e.submit(mc);
        DMI dmi;
        try {
            dmi = f.get();
            return dmi;
        } catch (InterruptedException | ExecutionException ex) {
            System.out.println(ex.getMessage());
            return null;
        }
    }
}

Example of output

Thread number: 150
Thread number: 150
Thread number: 150

If i use a p:poll to call the PostConstruct method continuously, than i would have something like:

Thread number: 150
Thread number: 150
Thread number: 150
Thread number: 151
Thread number: 151
Thread number: 151

I want something like:

Thread number: 148
Thread number: 149
Thread number: 150