Question

我正在尝试使用条件（Criteria Builder和CriteriaQuery）获得金额总和

但是我在编写代码时遇到错误; 这是我的代码

    public Long findAmountByCriteria(OrderCriteria orderCriteria) {

  final CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
  final CriteriaQuery<BigDecimal> query = criteriaBuilder.createQuery(BigDecimal.class);
  Root<Order> root = query.from(Order.class);

  query.select(criteriaBuilder.sum(root.get("amount")))
  .where(buildPredicateForOrderResponseCriteria(criteriaBuilder, orderCriteria, root));

  final TypedQuery<BigDecimal> typedQuery = entityManager.createQuery(query);
  return typedQuery.getSingleResult().longValue();
}

金额是BigDecimal值。

在选择mehtod中说，

The method select(Selection<? extends BigDecimal>) in the type CriteriaQuery<BigDecimal> is not applicable for the arguments (Expression<Object>)

总和方法

Bound mismatch: The generic method sum(Expression<N>) of type CriteriaBuilder is not applicable for the arguments (Path<Object>). The inferred type Object is not a valid substitute for the bounded parameter <N extends Number>

如何解决此问题。

Answer 1

而不是你正在做的事情

query.select(criteriaBuilder.sum(root.get("amount")))

尝试这样做

query.select(criteriaBuilder.sum(root.<BigDecimal> get("amount")))

使用CriteriaBuilder获取列的总和

1 个答案: