按相关实体筛选无联接的JPA条件

Question

我想知道如何使用JPA标准API通过相关实体的外键过滤实体。

假设我有两个实体如下：

public class Employee {
    @Id
    private Long id;
    ...
    @ManyToOne
    private Department department;
    ...
}

public class Department {
    @Id
    private Long id;
}

我想查询ID(1,2,3）部门下的员工。

select e.* from employee e where e.department_id in (1,2,3)

In<Object> inClause = criteriaBuilder.in(root.get(<attr>);
for (Long id : ids) {
    inClause.value(id);
}

Answer 1

Set<Integer> departments = new HashSet<Integer>();
departments.add(1);
departments.add(2);
departments.add(3);

CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Employee> cq = cb.createQuery(Employee.class);
Root<Employee> r = cq.from(Employee.class);
cq.select(r).where(r.get(Employee_.department).get(Department_.id).in(departments));
TypedQuery<Employee> query = em.createQuery(cq);
List<Employee> result = query.getResultList();