Hibernate CriteriaQuery where - ManyToOne 字段

Question

那是我的员工的片段 entity/class:

@Entity
@Table
public class Employee {
   ...
   @ManyToOne(.....)
   @JoinColumn(name="department_id")
   private Department department;
}

现在，我想获取特定部门的所有员工（具有特定 department_id 的员工）：

CriteriaBuilder builder = session.getCriteriaBuilder();
CriteriaQuery<Employee> criteriaQuery = builder.createQuery(Employee.class);
Root<Employee> employeeRoot = criteriaQuery.from(Employee.class);

criteriaQuery.select(employeeRoot);
criteriaQuery.where(builder.equal(employeeRoot.get(????????????), id));

这是我的问题。如何访问 Department.id？我知道我必须得到（{特定字段}）但我不知道如何。我应该先以某种方式加入那些表吗？期待您的回答！

Answer 1

您需要与您的亲戚 table 建立连接。例如：

CriteriaBuilder builder = session.getCriteriaBuilder();
CriteriaQuery<Employee> criteriaQuery = builder.createQuery(Employee.class);
Root<Employee> employeeRoot = criteriaQuery.from(Employee.class);

Join<Employee, Departament> join = from.join("department", JoinType.INNER);
criteriaQuery.where(builder.equal(join.get("specific_fied"), your_specific_fied));

TypedQuery<Employee> typedQuery = session.createQuery(criteriaQuery);

List<Employee> employees = typedQuery.getResultList();
for (Employee e : employees) {
    System.out.println(e.getName());
}

session.getTransaction().commit();
session.close();
entityManagerFactory.close();

如果您想要与此查询相同的内容：

SELECT c, p.name FROM Country c LEFT OUTER JOIN c.capital p

你可以构建这个：

  CriteriaQuery<Country> q = cb.createQuery(Country.class);
  Root<Country> c = q.from(Country.class);
  Join<Country> p = c.join("capital", JoinType.LEFT);
  q.multiselect(c, p.get("name"));

如果您构建与此查询相同的内容：

SELECT c FROM Country c JOIN FETCH c.capital

你可以构建这个：

  CriteriaQuery<Country> q = cb.createQuery(Country.class);
  Root<Country> c = q.from(Country.class);
  Fetch<Country,Capital> p = c.fetch("capital");
  q.select(c);

有关更多示例，请参阅 FROM clause (JPQL / Criteria API)

Hibernate CriteriaQuery where - ManyToOne 字段

Hibernate CriteriaQuery where - ManyToOne field

spring

hibernate

jpa

criteriaquery