parameters:
    darvin_admin.administrator.metadata.class:  Darvin\AdminBundle\Metadata\Metadata
    darvin_admin.administrator.metadata.entity: Darvin\AdminBundle\Entity\Administrator
    darvin_admin.administrator.metadata.config: @@DarvinAdminBundle/Resources/config/admin/administrator.yml

    darvin_admin.administrator.subscriber.class: Darvin\AdminBundle\EventListener\AdministratorSubscriber

services:
    darvin_admin.administrator.metadata:
        class:   %darvin_admin.administrator.metadata.class%
        factory: [ "@darvin_admin.metadata.factory", create ]
        arguments:
            - %darvin_admin.administrator.metadata.entity%
            - %darvin_admin.administrator.metadata.config%
        tags:
            - { name: darvin_admin.metadata }

    darvin_admin.administrator.subscriber:
        class: %darvin_admin.administrator.subscriber.class%
        arguments:
            - "@security.encoder_factory"
        tags:
            - { name: doctrine.event_subscriber }

parameters:
    darvin_admin.administrator.metadata.class:  Darvin\AdminBundle\Metadata\Metadata
    darvin_admin.administrator.metadata.entity: Darvin\AdminBundle\Entity\Administrator
    darvin_admin.administrator.metadata.config: @@DarvinAdminBundle/Resources/config/admin/administrator.yml

    darvin_admin.administrator.subscriber.class: Darvin\AdminBundle\EventListener\AdministratorSubscriber

services:
    darvin_admin.administrator.metadata:
        class:   %darvin_admin.administrator.metadata.class%
        factory: [ "@darvin_admin.metadata.factory", create ]
        arguments:
            - %darvin_admin.administrator.metadata.entity%
            - %darvin_admin.administrator.metadata.config%
        tags:
            - { name: darvin_admin.metadata }

    darvin_admin.administrator.subscriber:
        class:  %darvin_admin.administrator.subscriber.class%
        public: false
        arguments:
            - "@security.encoder_factory"
        tags:
            - { name: doctrine.event_subscriber }

Make Doctrine event subscriber service private.
Make Doctrine event subscriber service private.
