No entity found for query

getSingleResult()
getSingleResult的源码有一句： @throws EntityNotFoundException if there is no result


查不到结果时，它是抛异常的，不会返回null.
解决方式，将异常捕捉
try{
Query query =this.getJpaTemplate().getEntityManager().createNativeQuery(sql,SmpRole.class);
obj = (SmpRole)query.getSingleResult();

    }catch(NoResultException e){
return null;
    }