如何使用hibernate从java中的Jcombobox中检索主键id，它具有一对多关系？

我有实体项和单元，单元中的项是一对多相关的，我很难将数据输入到项中，其中项需要单元上的主键，而我不理解Jcombobox如何获取主键或ID

项目类实体

@Entity()
@Table(name = "item")
public class Item extends Record{   

    @Column(unique = false, nullable = false, length = 100)
    public String name;

    @Column(unique = false, nullable = false, length = 50)
    public double stock; // untuk menambah terus data jumlah  item dari supplier

    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "unit_id")
    public Unit unit;

@Entity()
@Table(name = "unit")
public class Unit extends Record {

    @Column(unique = false, nullable = false, length = 100)
    public String name;
    @Column(unique = false, nullable = false, length = 100)
    public String description;
    
  @OneToMany(mappedBy = "unit", cascade = { CascadeType.PERSIST, CascadeType.MERGE, CascadeType.DETACH,
      CascadeType.REFRESH })
    private List<Item> item;

类单位实体

@Entity()
@Table(name = "item")
public class Item extends Record{   

    @Column(unique = false, nullable = false, length = 100)
    public String name;

    @Column(unique = false, nullable = false, length = 50)
    public double stock; // untuk menambah terus data jumlah  item dari supplier

    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "unit_id")
    public Unit unit;

@Entity()
@Table(name = "unit")
public class Unit extends Record {

    @Column(unique = false, nullable = false, length = 100)
    public String name;
    @Column(unique = false, nullable = false, length = 100)
    public String description;
    
  @OneToMany(mappedBy = "unit", cascade = { CascadeType.PERSIST, CascadeType.MERGE, CascadeType.DETACH,
      CascadeType.REFRESH })
    private List<Item> item;

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如何在按钮上保存一对多？

不清楚。是否希望

JComboBox

显示不同“单元”名称的列表？我想在单元id项不是所需单元名称时存储2个相关实体，但不清楚。是否希望

JComboBox

显示不同“单元”名称的列表？我想存储2个相关实体，而单元id项不是所需的单元名称