如何删除spring data jpa中位于多个侧面的项？

Question

部门和员工之间存在双向的一对多关系。

@Setter
@Getter
@Entity
@Table(name = "t_department")
public class Department {
    @Id
    private String id;

    private String name;

    @OneToMany(mappedBy = "department",fetch = FetchType.EAGER,cascade = CascadeType.ALL)
    private List<Employee> employees;
}


@Setter
@Getter
@Entity
@Table(name = "t_employee")
public class Employee {
    @Id
    private String id;

    private String name;

    @ManyToOne(fetch = FetchType.EAGER)
    @JoinColumn(name = "dept_id")
    private Department department;
}

@Repository
public interface EmployeeRepository extends JpaRepository<Employee, String> {

}

在数据库中，我有这些记录。

t_department:
+----+------------+
| id | name       |
+----+------------+
| 2  | accounting |
| 3  | logistics  |
+----+------------+

t_employee:
+----+------+---------+
| id | name | dept_id |
+----+------+---------+
| 3  | Tom  | 2       |
| 4  | Tina | 3       |
+----+------+---------+

当我试图删除员工（id=“3”）时，

    @Test
    @Transactional
    public void should_delete_employee_success_when_delete_employee_given_a_exist_employee_id_in_DB() {
        employeeRepository.delete("3");
    }

但在控制台中，它只打印了2条select语句，没有删除：

Hibernate: select employee0_.id as id1_2_0_, employee0_.dept_id as dept_id3_2_0_, employee0_.name as name2_2_0_, department1_.id as id1_1_1_, department1_.name as name2_1_1_ from t_employee employee0_ left outer join t_department department1_ on employee0_.dept_id=department1_.id where employee0_.id=?
Hibernate: select employees0_.dept_id as dept_id3_2_0_, employees0_.id as id1_2_0_, employees0_.id as id1_2_1_, employees0_.dept_id as dept_id3_2_1_, employees0_.name as name2_2_1_ from t_employee employees0_ where employees0_.dept_id=?

我去看了数据库，什么都没做。

spring data jpa是如何工作的？我困惑了好几天。

提前感谢您的回答。

Answer 1

我发现，一旦部门知道谁与之相关，就不能删除与该部门相关的员工。我使用fetch=FetchType。双方都很急切，所以当我删除员工时，它将加载部门和该部门的员工。正确的做法是，您需要从部门的员工中删除该员工，然后将其删除。你可以试试这个：

    Optional<Employee> employeeOpt = employeeRepository.findById("3");
    if (employeeOpt.isPresent()) {
        Employee employee = employeeOpt.get();
        employee.getDepartment().getEmployees().removeIf(emp -> emp.getId().equals("3"));
        employeeRepository.deleteById("3");
    }

Answer 2

因为默认情况下，Spring测试被标记为仅回滚，并且SQL更改通常仅在事务提交时刷新到数据库。

然后，您需要（1）手动刷新更改以强制数据库写入：

public class SomeTest{

    @PersistenceContext 
    private EntityManager em;

    @Test
    @Transactional
    public void should_delete_employee_success_when_delete_employee_given_a_exist_employee_id_in_DB() {
        employeeRepository.delete("3");
        em.flush(); //force db update however transaction will still be rolled back
    }

或（2）

将事务设置为不仅用于回滚，您可以通过各种方式进行回滚，包括使用“提交”和“回滚”注释：

https://docs.spring.io/spring/docs/current/spring-framework-reference/testing.html#integration-测试注释spring

Answer 3

CrudRepository有方法删除（