Question

我正在尝试创建OneToMany / ManyToOne关系。除删除操作外，所有操作都按预期工作，这意味着，当删除OwningSide时，NonOwningSide也会被删除。

有没有办法防止这种行为，所以如果删除OwningSide，NonOwningSide的owningSide_id将被设置为NULL？

伪代码

public class OwningSide {

  @OneToMany(
      cascade = {CascadeType.ALL},
      mappedBy = "owningSide")
  @LazyCollection(LazyCollectionOption.FALSE)
  @JsonManagedReference  
  private List<NonOwningSide> nonOwningSide;

}

public class NonOwningSide {

  @ManyToOne(
      cascade = {CascadeType.ALL},
      fetch = FetchType.EAGER)
  @JoinColumn(name = "owningSide_id")
  @JsonBackReference
  private OwningSide owningSide;

}

Answer 1

首先在自己身边更改 cascade = CascadeType.PERSIST 。

public class OwningSide {

  @OneToMany(
      cascade = {CascadeType.PERSIST}, mappedBy = "owningSide")
  @LazyCollection(LazyCollectionOption.FALSE)
  @JsonManagedReference  
  private List<NonOwningSide> nonOwningSide;

}

public class NonOwningSide {

  @ManyToOne(
      cascade = {CascadeType.ALL}, fetch = FetchType.EAGER)
  @JoinColumn(name = "owningSide_id")
  @JsonBackReference
  private OwningSide owningSide;

}

JPA中的CascadeType。值cascade=ALL相当于 * cascade={PERSIST, MERGE, REMOVE, REFRESH, DETACH}。

/** Cascade all operations */
ALL,

/** Cascade persist operation */
PERSIST,

/** Cascade merge operation */
MERGE,

/** Cascade remove operation */
REMOVE,

/** Cascade refresh operation */
REFRESH

要执行此操作，在创建表并向NonOwningSide添加外键时，请提及级联类型为set null以删除owningSide，如下所示。

- 这次，使用 on delete set null ：

创建它

alter table NonOwningSide add constraint constraintName 
foreign key (id) references OwningSide(id) on delete set null

Answer 2

你必须将cjild的对象设置为null

for (NonOwningSide child : OwningSide.getChildren()) {
child.setNonOwningSide(null);

} 使用Session.delete（OwningSide）;

Hibernate OneToMany / ManyToOne删除Cascade

2 个答案: