namespace AppBundleEntity;

use DoctrineORMMapping as ORM;

/**
 * @ORMEntity
 * @ORMTable(name="user")
 */
class User
{
    /**
     * @ORMColumn(type="integer")
     * @ORMId
     * @ORMGeneratedValue(strategy="AUTO")
     */
    private $id;

    /**
     * @ORMColumn(type="string", length=100)
     */
    private $username;
 ...

...
/**
     * @Route("/", name="homepage")
     * @param Request $request
     * @return Response
     */
    public function indexAction(Request $request)
    {
        $manager = $this->getDoctrine()->getManager();

        $user = new User();
        $user->setUsername('jiro');
        $user->setPassword('fantozzi');

        try{
            $manager->persist($user);
            $manager->flush();

        }catch (Exception $exception){
            var_dump($exception->getMessage());
        }
        return new Response("<h1>It works</h1>");
    }
...

doctrine:
    dbal:
        driver: pdo_mysql
        host: '%database_host%'
        port: '%database_port%'
        dbname: '%database_name%'
        user: '%database_user%'
        password: '%database_password%'
        charset: utf8mb4
        default_table_options:
          charset: utf8mb4
          collate: utf8mb4_unicode_ci
    orm:
        auto_generate_proxy_classes: '%kernel.debug%'
        naming_strategy: doctrine.orm.naming_strategy.underscore
        auto_mapping: true