Subquery filter sum with one to many in JPA

Question

I have 2 entities:

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

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

and

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

    private Integer numberOfClaims;
}

Now I want to build a javax.persistence.criteria.Predicate to find all Orders with numberOfClaims greater then x.

Answer 1

Try:

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

See some correlated subquery examples in the following cmobilecom-jpa developer guide:

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

Using Criteria API:

(refer to the section: "Correlate To Root" of chapter "Subquery")

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);