Console/Symfony Call command from controller

I have some issues with Console when I try to call a Command from a Controller. I found a way in the Symfony CookBook : http://symfony.com/doc/current/cookbook/console/command_in_controller.html

It seems doesn't work... Maybe I forgot something!

Command :

namespace AppBundle\Command;

use Symfony\Component\Console\Command\Command;
use Symfony\Component\Console\Input\InputArgument;
use Symfony\Component\Console\Input\InputInterface;
use Symfony\Component\Console\Input\InputOption;
use Symfony\Component\Console\Output\OutputInterface;

class GreetCommand extends Command
{
    protected function configure()
    {
        $this
            ->setName('demo:greet')
            ->setDescription('Greet someone')
            ->addArgument(
                'name',
                InputArgument::OPTIONAL,
                'Who do you want to greet?'
            )
            ->addOption(
                'yell',
                null,
                InputOption::VALUE_NONE,
                'If set, the task will yell in uppercase letters'
            )
        ;
    }

    protected function execute(InputInterface $input, OutputInterface $output)
    {
        $name = $input->getArgument('name');
        if ($name) {
            $text = 'Hello '.$name;
        } else {
            $text = 'Hello';
        }

        if ($input->getOption('yell')) {
            $text = strtoupper($text);
        }

        $output->writeln($text);
    }
}

(The command works well in cmd)

Controller :

namespace AppBundle\Controller;

use Symfony\Bundle\FrameworkBundle\Controller\Controller;
use Symfony\Component\Console\Application;
use Symfony\Component\Console\Input\ArrayInput;
use Symfony\Component\Console\Output\BufferedOutput;


class MainController extends Controller
{
    public function indexAction()
    {
        $kernel = $this->get('kernel');
        $application = new Application($kernel);
        $application->setAutoExit(false);

        $input = new ArrayInput(array(
            'command' => 'demo:greet'
        ));

        $output = new BufferedOutput();
        $application->run($input, $output);

        $content = $output->fetch();

        dump($content);die;
    }
}

Response

[Symfony\Component\Console\Exception\CommandNotFoundException] There are no commands defined in the "demo" namespace. 

Thank you in advance for your help.