Hibernate 使用 ManyToOne 删除所有引用 object 单向的对象关联

Question

I have a ModuleData object and a Setting object that references this ModuleData object, but the ModuleData object does not have any reference to the Setting object. Does Hibernate automatically delete the objects that reference ModuleData and if not, how do I accomplish that Hibernate does this.

ModuleData.java

@Entity
@Table(name = "modules")
public class ModuleData {

    @Id
    @GeneratedValue
    @Column(name = "id", updatable = false, nullable = false)
    private long id;

    @Column(name = "name")
    private String name;

    @Column(name = "version")
    private String version;
}

Setting.java

@Entity
@Table(name = "settings", uniqueConstraints = @UniqueConstraint(columnNames = {"settingKey"}))
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public class Setting {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;

    @Column(name = "settingKey", nullable = false)
    private String key;

    @Column
    private String value;

    @ManyToOne
    @JoinColumn(name = "moduleId", nullable = false)
    private ModuleData module;

I will delete by session.delete(moduleData) .

Answer 1

You can add the other side of the relation (ie add the Setting property to the ModuleData class), and then use Java Persistence 'cascade types' to accomplish this. Specifically the CascadeType.REMOVE will give you the desired behavior. From this great tutorial , your ModuleData class would reference its Setting child similar to this:

@OneToMany(cascade = CascadeType.ALL, mappedBy = "post", orphanRemoval = true)
private List<Comment> comments = new ArrayList<>();

so it would look something like:

@OneToMany(cascade = CascadeType.REMOVE, orphanRemoval = true, ...)
private List<Setting> settings;

Another great tutorial on cascade types:

• https://www.baeldung.com/jpa-cascade-types