VirtualizationConnectorEntityMgr.java 文件源码

public static boolean isControllerTypeUsed(String controllerType, EntityManager em) {

        Long count = 0L;
        try {
            CriteriaBuilder cb = em.getCriteriaBuilder();

            CriteriaQuery<Long> query = cb.createQuery(Long.class);

            Root<VirtualizationConnector> root = query.from(VirtualizationConnector.class);

            query = query.select(cb.count(root))
                    .where(cb.equal(root.get("controllerType"), controllerType));

            count = em.createQuery(query).getSingleResult();
        } catch (Exception e) {
            // Ignore this exception
        }

        return count > 0;
    }