在@OneToMany中,在hibernate中删除set null

Question

我有一个部门实体,其关系如下:

1. 许多部门可以在一个父部门:

   @ManyToOne
   @JoinColumn(name = "ik_parent_department_id")
   private Department parentDepartment;
   

2. 一个父部门可以有很多部门:

   @OneToMany(mappedBy = "parentDepartment")
   private Set<Department> children = new HashSet<Department>(0);
   

我想实现下一个:当我删除一个部门时,该部门所有子项的ik_parent_department_id参数都设置为null.任何想法如何做到这一点？

Answer 1

您必须ik_parent_department_id明确地将子项设置为null.

Department parentDepartment = (Department) session.load(Department.class, id);
session.delete(parentDepartment);
for (Department child : parentDepartment.getChildren()){
    child.setParentDepartment(null);
} 
session.flush();

通过级联,您只能设法删除子级Departments.

Answer 2

使用 JPA，在父母中Entity你可能有类似的东西

@OneToMany(mappedBy="parent", cascade={CascadeType.PERSIST})
Collection<Child> children;

而为了避免可能出现的重复着“集零码”及完整性违反了父去除异常父落实Entity还

@PreRemove
private void preRemove() {
   children.forEach( child -> child.setParent(null));
}

Answer 3

只需编码:

for (Department child : parent.getChildren()) {
    child.setParentDepartment(null);
}
session.delete(parent);