symfony空白捆绑类加载器

Question

我无法弄清楚为什么symfony2加载一个像Bundle这样的Bundle的空类： AppKernel.php

<?php

use Symfony\Component\HttpKernel\Kernel;
use Symfony\Component\Config\Loader\LoaderInterface;

class AppKernel extends Kernel
{
    public function registerBundles()
    {
        $bundles = array(
            new Symfony\Bundle\FrameworkBundle\FrameworkBundle(),
            new Symfony\Bundle\SecurityBundle\SecurityBundle(),
            new Symfony\Bundle\TwigBundle\TwigBundle(),
            new Symfony\Bundle\MonologBundle\MonologBundle(),
            new Symfony\Bundle\SwiftmailerBundle\SwiftmailerBundle(),
            new Symfony\Bundle\AsseticBundle\AsseticBundle(),
            new Doctrine\Bundle\DoctrineBundle\DoctrineBundle(),
            new Sensio\Bundle\FrameworkExtraBundle\SensioFrameworkExtraBundle(),
            new AppBundle\AppBundle(),
        );

与最后一行new AppBundle\AppBundle()

一样

src/AppBundle/AppBundle.php看起来像这样：

<?php

namespace AppBundle;

use Symfony\Component\HttpKernel\Bundle\Bundle;

class AppBundle extends Bundle
{
}

我真的不明白。我读了两本Symfony2书（书和食谱），我找不到答案。

谢谢。