在 JPA 中使用继承时的复合外键问题

Posted 2023-03-28

【中文标题】在 JPA 中使用继承时的复合外键问题

【英文标题】：Composite Foreign Key Issue while using Inheritance in JPA

【发布时间】：2011-12-29 13:52:55

【问题描述】：

我有一个 JPA 实体 StatsEntity，它有一个复合主键，它也是另一个实体名册的外键。这是使用 @JoinColumns(@JoinColumn...) 注释设置为 @OneToOne 关系。

StatsEntity 扩展了另一个实体 CoreStatsEntity，它设置为 @MappedSuperClass 其中 RosterEntity 使用 SINGLE_TABLE 继承策略扩展了另一个实体 CoreRoster。

@Entity
@Table(name = "Stats")
@IdClass(value = StatsEntity.Key.class)
public class StatsEntity extends CoreStatsEntity implements
    Stats 

@Id
private Integer competitionId;

@Id
private Integer playerId;

@Id
private Integer teamId;

@OneToOne
@JoinColumns(
        @JoinColumn(name = "competitionId", referencedColumnName = "competitionId", insertable = false, updatable=false),
        @JoinColumn(name = "playerId", referencedColumnName = "personId", insertable = false, updatable=false),
        @JoinColumn(name = "teamId", referencedColumnName = "teamId", insertable = false, updatable=false) )
private RosterEntity roster;


....

StatsEntity.Key

 @Embeddable
public static class Key implements Serializable 

    private static final long serialVersionUID = -7349082038890396790L;

    @Column(name = "competitionId", insertable = false, updatable = false)
    private Integer competitionId;

    @Column(name = "playerId", insertable = false, updatable = false)
    private Integer playerId;

    @Column(name = "teamId", insertable = false, updatable = false)
    private Integer teamId;

    public Key() 
        super();
    

    public Key(int competitionId, int playerId, int teamId) 
        this.competitionId = Integer.valueOf(competitionId);
        this.playerId = Integer.valueOf(playerId);
        this.teamId = Integer.valueOf(teamId);
    

    public int getTeamId() 
        return teamId.intValue();
    

    public void setTeamId(int teamId) 
        this.teamId = Integer.valueOf(teamId);
    

    public int getPlayerId() 
        return playerId.intValue();
    

    public void setPlayerId(int playerId) 
        this.playerId = Integer.valueOf(playerId);
    

    public int getCompetitionId() 
        return competitionId.intValue();
    

    public void setCompetitionId(int CompetitionId) 
        this.competitionId = Integer.valueOf(CompetitionId);
    

    /*
     * (non-Javadoc)
     * 
     * @see java.lang.Object#equals(java.lang.Object)
     */
    @Override
    public boolean equals(Object object) 
        if (object == this) 
            return true;
        
        if (!(object instanceof Key)) 
            return false;
        

        Key other = (Key) object;
        return Utils.equals(other.getTeamId(), this.getTeamId())
                && Utils.equals(other.getPlayerId(), this.getPlayerId())
                && Utils.equals(other.getCompetitionId(),
                        this.getCompetitionId());
    

    /*
     * (non-Javadoc)
     * 
     * @see java.lang.Object#hashCode()
     */
    @Override
    public int hashCode() 
        return Utils.hashCode(this.teamId, this.playerId,
                this.competitionId);

    

    /*
     * (non-Javadoc)
     * 
     * @see java.lang.Object#toString()
     */
    @Override
    public String toString() 
        return Utils.toString("CompetitionPlayerStatsEntity.Key",
                this.teamId, this.playerId, this.competitionId);
    

CoreStatsEntity.java

@MappedSuperclass
public abstract class CoreStatsEntity

名册实体

 @Entity
 @DiscriminatorValue("20")
  public class RosterEntity extends
    CoreRosterEntity  

    //.... attributes, getters, setters

    

CoreRosterEntity.java

@Entity
@DiscriminatorValue("0")
@Table(name="Roster")
@IdClass(CoreRoster.Key.class)           

@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name="discriminator", discriminatorType=DiscriminatorType.INTEGER)
public class CoreRosterEntity  

        private static final long serialVersionUID = 1521639115446682871L;

@Id
private Integer competitionId;

@Id
private Integer teamId;

@Id
private Integer playerId;

//.. getters, setters and other attributes

CoreRoster.java 中的CoreRoster.Key.class

@Embeddable
public static class Key implements Serializable 

    private static final long serialVersionUID = 2L;

    @Column(name="competitionId", nullable=false)
    private Integer competitionId;

    @Column(name="teamId", nullable=false)
    private Integer teamId;

    @Column(name="personId", nullable=false)
    private Integer playerId;

    public Key() 
        super();
    

    public Key(int competitionId, int teamId, int playerId) 
        this.competitionId = Integer.valueOf(competitionId);
        this.teamId = Integer.valueOf(teamId);
        this.playerId = Integer.valueOf(playerId);
    

    public int getPlayerId() 
        return playerId.intValue();
    

    public void setPlayerId(int playerId) 
        this.playerId = Integer.valueOf(playerId);
    

    public int getTeamId() 
        return teamId.intValue();
    

    public void setTeamId(int teamId) 
        this.teamId = Integer.valueOf(teamId);
    

    public int getCompetitionId() 
        return this.competitionId.intValue();
    

    public void setCompetitionId(int competitionId) 
        this.competitionId = Integer.valueOf(competitionId);
    

    /*
     * (non-Javadoc)
     * @see java.lang.Object#equals(java.lang.Object)
     */
    @Override
    public boolean equals(Object object) 
        if (object == this)  return true; 
        if (!(object instanceof Key))  return false; 

        Key other = (Key) object;
        return Utils.equals(other.getCompetitionId(), this.getCompetitionId()) &&
               Utils.equals(other.getTeamId(), this.getTeamId()) &&
               Utils.equals(other.getPlayerId(), this.getPlayerId());
    

    /*
     * (non-Javadoc)
     * @see java.lang.Object#hashCode()
     */
    @Override
    public int hashCode() 
        return Utils.hashCode(this.competitionId, this.teamId,
                              this.playerId);
    

    /*
     * (non-Javadoc)
     * @see java.lang.Object#toString()
     */
    @Override
    public String toString() 
        return Utils.toString("CoreRoster.Key",
                              this.competitionId, this.teamId,
                              this.playerId);
    

当我持久化 StatsEntity 时，它会被持久化。但是当我尝试使用主键找到它时，它给了我一个错误：

    StatsEntity playerStats = new StatsEntity();
    //set all values
this.persist(playerStats);              
entityManager.find(StatsEntity.class, playerStats.getId()); //getId returns the composite primary key

 java.lang.IllegalArgumentException: Provided id of the wrong type for class   com.sports.RosterEntity. Expected: class com.sports.CoreRoster$Key, got class com.espn.sports.StatsEntity$Key

我的第一个问题是，我给出的@OneToOne 映射是否正确？ 如果正确，那么当我尝试使用主键查找实体时为什么会出现此错误。

【参考方案1】：

您尚未发布完整的源代码，尤其是您的主键类的源代码，但您已将外键映射为只读，这在多次映射单个列时是必需的。

但是，我看到您的 id 列与作为 RosterEntity 的外键的 3 列完全相同，对吗？在这种情况下，这个 RosterEntity 应该是您的 ID，这将简化您的设计。

getId() 方法的返回类型是什么？问题可能与 IdClass 的定义或用法有关。

【讨论】：

已编辑问题。 getId的返回类型是Object，但我返回的是StatsEntity.Key的对象。让我试试你的建议

Roster.Key 不能作为 ID，因为其中的列名称不同。（personId 而不是 playerId）

对 DB 列添加了一个小改动（感谢 DBA），现在我将密钥设置为 RosterEntity。工作。谢谢