JPA中一对多的子查询过滤器总和

Question

我有 2 个实体：

@Entity
class Order {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;

    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    private Set<Contract> contracts= new HashSet<>();
}

和

@Entity
class Contract {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;

    private Integer numberOfClaims;
}

现在我想建立一个javax.persistence.criteria.Predicate 来查找所有numberOfClaims 大于x 的订单。

Answer 1

试试：

select o from Order o where
(select sum(c.numberOfClaims) from o.contracts c) > x

在以下 cmobilecom-jpa 开发者指南中查看一些相关的子查询示例：

https://cmobilecom.com/docs/jpa/latest/devguide/index.html

使用标准 API：

（请参阅“子查询”一章的“与根相关”部分）

CriteriaQuery<Order> criteriaQuery = criteriaBuilder.createQuery(Order.class);
Root<Order> root = criteriaQuery.from(Order.class);
criteriaQuery.select(root);
criteriaQuery.distinct(true);

// Subquery: correlate the root of parent query
Subquery<Integer> subquery = criteriaQuery.subquery(Integer.class);
Root<Order> subqueryRoot = subquery.correlate(root);
Join<Order, Contract> contracts = subqueryRoot.join("contracts");
subquery.select(criteriaBuilder.sum(contracts.get("numberOfClaims")));

Predicate restriction = criteriaBuilder.greaterThan(subquery, x);
criteriaQuery.where(restriction);