@Override @Transactional public void deleteMultimedia(Multimedia multimedia) { Validate.notNull(multimedia, "multimedia can not be null"); final EntityManager entityManager = this.getEntityManager(); final MultimediaImpl multimediaImpl = entityManager.find(MultimediaImpl.class, multimedia.getMultimediaId()); final ConferenceUser creator = multimediaImpl.getCreator(); final ConferenceUserImpl creatorImpl = this.conferenceUserDao.getUser(creator.getUserId()); creatorImpl.getMultimedias().remove(multimediaImpl); entityManager.remove(multimediaImpl); // entityManager.remove(creatorImpl); }