@Service
public class TestDaoImpl implements TestDao {
    private static final Logger logger = LoggerFactory.getLogger(TestDaoImpl.class);

    protected EntityManager entityManager = null;


    @PersistenceContext
public void setEntityManager(EntityManager entityManager) {
        this.entityManager 
 
= entityManager;
    }

    @Override
public void save(TestEntity entity) {
        entityManager.persist(entity);
    }

    public void clear(){
        try {
            HibernateEntityManager hEntityManager = (HibernateEntityManager)entityManager;
            Session session = hEntityManager.getSession();
            Query query = session.createSQLQuery("delete from test"
 
);
            query.executeUpdate();
        }catch (Exception e){
            logger.error(e.getMessage(),e);
        }
    }

}

當然，別忘了，在service層，得加上@Transactional註解（因為hibernate預設，autocommit=false）