jpa一對多查詢

Specification<Customer> spec = new Specification<Customer>() {
            @Override
            public Predicate toPredicate(Root<Customer> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder criteriaBuilder) {
                Path<Object> custName = root.get("custName");//客戶名
               
                Predicate predicate1 = criteriaBuilder.equal(custName, "紅");
               
                return p;
            }
        };
        Customer customer = customerDao.findOne(spec);
        return customer.isPresent() ? customer.get() : null;