JPA 自關聯 PO 映射

JPA 自關聯 PO映射

數據庫設計：
id關聯Parent_id.

實體類設計：
*CascadeType的各種屬性決定級聯查詢、更新、刪除的方式 *

@ManyToOne(cascade = CascadeType.REFRESH, fetch = FetchType.EAGER)
@JoinColumn(name = "parent_id", referencedColumnName = "id")
private Department parentDepartment;

@OneToMany(cascade = {CascadeType.REMOVE, CascadeType.REFRESH}, fetch = FetchType.EAGER, mappedBy = "parentDepartment")
private List<Department> childDepartment;

邏輯層刪除方法：

Optional<Department> optionalDepartment = departmentDao.findById(departmentVO.getId());
if (optionalDepartment.isPresent()) {
    Department department = optionalDepartment.get();//要先查詢實體並封裝，否則刪除報錯
    departmentDao.delete(department);
}