问Symfony2 Redis Validator，string而不是ClassMetadata

EN

framework:
    validation:
        cache: validator.mapping.cache.redis
    serializer:
        cache: serializer.mapping.cache.redis
    session:
        handler_id: session.handler.redis

doctrine:
    orm:
        auto_mapping: true
        metadata_cache_driver:
            type: redis
            host: "%redis.ip%"
            port: "%redis.port%"
            instance_class: Redis
            class: RedisCache
        query_cache_driver:
            type: redis
            host: "%redis.ip%"
            port: "%redis.port%"
            instance_class: Redis
            class: RedisCache
        result_cache_driver:
            type: redis
            host: "%redis.ip%"
            port: "%redis.port%"
            instance_class: Redis
            class: RedisCache

services:
    serializer.mapping.cache.redis:
        class: Doctrine\Common\Cache\RedisCache

    validator.mapping.cache.redis:
        class: Symfony\Component\Validator\Mapping\Cache\DoctrineCache
        arguments: ['@doctrine.cache.redis']

    redis:
        class: Redis
        calls:
            - [ connect, [ '%redis.ip%', '%redis.port%' ]]

    doctrine.cache.redis:
        class: Doctrine\Common\Cache\RedisCache
        calls:
            - [setRedis, ["@redis"]]

    session.handler.redis:
        class: Symfony\Component\HttpFoundation\Session\Storage\Handler\NativeSessionHandler

    serializer.mapping.cache.memcached:
        class: Doctrine\Common\Cache\MemcachedCache


doctrine_cache:
    providers:
        redis_cache:
            redis:
                connection_id: redis