当使用继承和ManyToOne与JPA的关系时如何级联删除 [英] How to cascade delete when using inheritance and ManyToOne relationship with JPA

问题描述

我正在用spring实现一个简单的用户管理系统。为了实现更好的模型结构，我使用继承。该系统建立在三个班级上。包含一般信息的 userdata 类。继承并扩展用户类的父类类，最后是包含父对象的子类类。

我想要做的是通过删除父来删除所有的孩子（被称为父母）对象。

我已经能够通过我的视图在mySQL-DB上保存/删除对象，因此存储库/服务/控制器似乎可以工作。 / b>

为了让您更好地理解我的情况，我在下面加了一些代码。

我的用户类：

  @Entity 
 @Inheritance（strategy = InheritanceType.JOINED）
 public class UserData实现了Persistable< String> {
 
 private static final long serialVersionUID = 1L; 
 
 @Id 
 @NotNull 
私人字符串用户名; 
 @NotNull 
私人字符串密码; 
 @NotNull 
 private String firstName; 
 @NotNull 
私人字符串姓氏; 
  

我的父母继承自User的类和持有一组Child：

  @Entity 
公共类父扩展用户数据{
 
 private static final long serialVersionUID = 1L; 
 
私人字符串imgName; 
 @OneToMany（fetch = FetchType.EAGER）
 @ElementCollection 
私人设置< Child>儿童; 
  

我的 Child

  @Entity 
 @Transactional 
 public class Child实现Persistable< Long> {
 
 private static final long serialVersionUID = 1L; 
 
 @Id 
 @GeneratedValue（strategy = GenerationType.AUTO）
私有长ID; 
 @NotNull 
 private String firstName; 
 @NotNull 
私人字符串姓氏; 
 @NotNull 
私人字符串生日; 
 @NotNull 
 @ManyToOne（可选= false）
私有父亲1; 
  

希望任何人都能告诉我如何实现 DELETE ON CASCADE 在我的系统中。

解决方案

添加 mappedBy =parent1，cascade = CascadeType.ALL ，添加到父中的@OneToMany注释 Set< Child>子女可以工作。

I'm implementing a simple user managment system with spring. To achieve better model structure I use inheritance. The system is build on three classes. The userdata class which holds general information. The parent class which inherits and extends the user class and finally a child class which holds a parent object.

What I'm trying to do is to get all children (who are referred to a parent) deleted by deleting the parent object.

I'm already able to save/delete objects to/from my mySQL-DB over my view, so the repositories/services/controllers seem to work.

To give you better understanding of my situation I put some code below.

My User Class:

@Entity
@Inheritance(strategy = InheritanceType.JOINED)
public class UserData implements Persistable<String> {

private static final long serialVersionUID = 1L;

@Id
@NotNull
private String username;
@NotNull
private String password;
@NotNull
private String firstName;
@NotNull
private String lastName;

My Parent Class which inherits from User and holds a set of Child:

@Entity
public class Parent extends UserData {

private static final long serialVersionUID = 1L;

private String imgName;
@OneToMany(fetch = FetchType.EAGER)
@ElementCollection
private Set<Child> children;

My Child class which holds a Parent object

@Entity
@Transactional
public class Child implements Persistable<Long> {

private static final long serialVersionUID = 1L;

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
@NotNull
private String firstName;
@NotNull
private String lastName;
@NotNull
private String birthday;
@NotNull
@ManyToOne(optional = false)
private Parent parent1;

Hope anyone can tell me how I achieve DELETE ON CASCADE in my system.

解决方案

Adding mappedBy = "parent1", cascade = CascadeType.ALL, orphanRemoval = true to the @OneToMany annotation in parent by Set<Child> children works.

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