Hibernate中的@onetomany注释不正确

Question

我正在研究Hibernate，并且遇到了与Hibernate注释相关的非明确情况。

假设我们有两个实体：

主题和发言人

一个话题可能与许多发言者有关。一个主题可能有几个发言者。 一位发言者可以参加几个主题。

如下所示：

我的普通应用程序包含两个实体类：主题类和扬声器类

Topic类包含注释，通过TOPIC_SPEAKERS表声明与SPEAKERS的一对多关系。如果TOPIC_SPEAKERS表不存在，则会在运行时生成。

Topic.class（跳过不相关的代码）

@Entity
@Table(name="TOPICS")
public class Topic implements Serializable {

    @Id
    @GeneratedValue
    private long topicId;      

    @OneToMany(cascade = CascadeType.ALL)
    @JoinTable(name = "TOPIC_SPEAKERS",
    joinColumns = {
        @JoinColumn(name = "topicId")},
    inverseJoinColumns = {
        @JoinColumn(name = "speakerId")})
    private List<Speaker> speakersList;

和扬声器类标题：

@Entity
@Table(name="SPEAKERS")
public class Speaker implements Serializable {

    @Id
    @GeneratedValue
    private long speakerId;

    private String speakerName;

我在SPEAKERS表中添加了两条记录，它看起来像是：

然后我参考第一位发言人（John Doe）向TOPICS表添加了一个主题。

TOPICS table:

and TOPIC_SPEAKERS table:

一切正常，直到我试图添加另一个话题，指的是第一个发言者（John Doe）。即，将第二个主题添加到TOPICS表中，将“TOPIC_SPEAKERS”中的“第二个主题”引用到第一个发言者（John Doe）。

产生的TOPIC_SPEAKERS应该是这样的（65536 - John Doe的id）：

#     TOPICID     SPEAKERID
1      131072       65536
2      132111       65536

但是Hibernate不允许向具有重复SPEAKERID值的TOPIC_SPEAKERS插入记录。

我收到以下错误：

could not insert collection: [simpledbtest.model.Topic.speakersList#163840]
SEVERE: The statement was aborted because it would have caused a duplicate key value 
in a unique or primary key constraint or unique index identified by 'SQL130314230217010' 
defined on 'TOPIC_SPEAKERS'.

....
Caused by: java.sql.SQLIntegrityConstraintViolationException: The statement was aborted because 
it would have caused a duplicate key value in a unique or primary key constraint or unique 
index identified by 'SQL130314230217010' defined on 'TOPIC_SPEAKERS'.

....

Caused by: org.apache.derby.client.am.SqlException: The statement was aborted because it 
would have caused a duplicate key value in a unique or primary key constraint or unique index 
identified by 'SQL130314230217010' defined on 'TOPIC_SPEAKERS'.

我的问题 - 如何更改Topic类中的注释以允许生成的TOPIC_SPEAKERS表中的重复列值？

谢谢。

Answer 1

您正在描述ManyToMany关系，并且必须使用@ManyToMany注释。像这样：

@Entity
@Table(name="TOPICS")
public class Topic implements Serializable {

    @Id
    @GeneratedValue
    private long topicId;      

    @ManyToMany(cascade = CascadeType.ALL)
    @JoinTable(name = "TOPIC_SPEAKERS",
    joinColumns = {
        @JoinColumn(name = "topicId")},
    inverseJoinColumns = {
        @JoinColumn(name = "speakerId")})
    private Set<Speaker> speakersList;




@Entity
@Table(name="SPEAKERS")
public class Speaker implements Serializable {

    @Id
    @GeneratedValue
    private long speakerId;

    @ManyToMany(mappedBy = "speakersList")
    private Set<Topic> topics;

    private String speakerName;