创建一个symfony2服务

services:
    app.my_service:
        class: AppBundle\Service\MyService
        arguments:
            - '@doctrine.orm.entity_manager'

namespace AppBundle\Service;

use Doctrine\ORM\EntityManager;

class MyService
{
    private $em;

    public function __construct(EntityManager $em)
    {
        $this->em = $em;
    }

    public function doSomething()
    {
        // 在这里编写你的服务代码
    }
}

namespace AppBundle\Controller;

use Sensio\Bundle\FrameworkExtraBundle\Configuration\Route;
use Symfony\Bundle\FrameworkBundle\Controller\Controller;
use Symfony\Component\HttpFoundation\Request;
use AppBundle\Service\MyService;

class DefaultController extends Controller
{
    /**
     * @Route("/", name="homepage")
     */
    public function indexAction(Request $request, MyService $myService)
    {
        // 在这里使用你的服务
        $myService->doSomething();

        // ...
    }
}