Question

通过了解hibernate如何映射集合bidiractional，我有一点问题。

通缉如下：表模式：

事件（e_id，date，i_id）

info（i_id，detailDesc）

我有多个事件和一些信息对象，它们将详细信息汇总到x事件。作为对象，我有不同的事件对象和一些应该包含事件对象列表的Info对象。与Info Object相关的Event Objects应该有一个相关的info对象，请参阅下面的类信息。

@Entity
@Table(name = "info")
public class Info {
    @Id
    @GenericGenerator(name = "gen", strategy = "increment")
    @GeneratedValue(generator = "gen")
    @Column(name = "i_id")
    private long id;

    @JoinTable(name = "events",
            joinColumns = @JoinColumn(name = "e_id"),
            inverseJoinColumns = @JoinColumn(name = "i_id"))
    @OneToMany(targetEntity = Event.class, cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    private List<Event> events;

    String detailDesc;

}


@Entity
    @Table(name = "event") 
    public class Event {
        @Id
        @GenericGenerator(name = "gen", strategy = "increment")
        @GeneratedValue(generator = "gen")
        @Column(name = "e_id")
        private long id;

        // Can be NULL 
        @ManyToOne(targetEntity = Info.class, fetch = FetchType.EAGER, cascade = CascadeType.ALL, optional = true)
        @JoinColumn(name = "i_id")
        private Info info;

       private Date date;

    }

就像现在一样，hibernate表示重复条目或外键约束失败（event，CONSTRAINT FK_r9sdjn6nelyo5be86vu0b2prs FOREIGN KEY（e_id）参考info（{{1} }））

Answer 1

您的映射不正确。鉴于您的架构，您没有使用JoinTable，因此在@ManyToOne侧设置@JoinColumn（就像您所拥有的那样）并简单地使用＆＃39; mappedBy＆＃39;相反的。确保关系的两侧都设置为确保级联按预期工作。

如果您确实想要使用连接表（而不是事件＆gt;信息中的FK），那么您可以将现有的@JoinTable移动到@ManyToOne并删除@JoinColumn。无论您使用的是@JoinTable还是@JoinColumn，反面都将保持如下。

@Entity
@Table(name = "info")
public class Info {

    @Id
    @GenericGenerator(name = "gen", strategy = "increment")
    @GeneratedValue(generator = "gen")
    @Column(name = "i_id")
    private long id;


    @OneToMany(mappedBy="info" cascade = CascadeType.ALL)
    private List<Event> events;

    String detailDesc;

    //set both sides of the relationship
    public void addEvent(Event event){
        event.setInfo(this);
        events.add(event);
    }

    public List<Event> getEvents(){
        //return unmodifiable list or iterator to force clients through addEvent() method
    }

}


@Entity
@Table(name = "event") 
 public class Event {
    @Id
    @GenericGenerator(name = "gen", strategy = "increment")
    @GeneratedValue(generator = "gen")
    @Column(name = "e_id")
    private long id;

    @ManyToOne(cascade = CascadeType.ALL, optional = true)
    @JoinColumn(name = "i_id")
    private Info info;

   private Date date;

 }

Hibernate Mapping理解

1 个答案: