嵌入式 ID 映射失败并出现 DescriptorException：应该为主键字段定义一个非只读映射 (EclipseLink)

Question

我有以下非常简单的设计：

一个俱乐部有多个团队，每个团队都有一个团队类型代码（性别 - 年龄组代码）加上一个序数（团队）编号，例如20 岁以上的男性将是“MO20”，序号代表该年龄组的第一、第二等团队。这是Teams 的PK。你明白了。

俱乐部映射：

@Entity
@Table(name = "Clubs")
public class Club implements Serializable
{
    private static final long serialVersionUID = 1L;

    @Id
    @Column
    private Integer id;

    @Basic(optional = false)
    @Column
    private String name;

    @Basic(optional = false)
    @Column
    private String code;

    @OneToMany(mappedBy = "club")
    private List<Team> teams;

    ...
}

团队映射：

@Entity
@Table(name = "Teams")
public class Team implements Serializable
{
    private static final long serialVersionUID = 1L;

    @EmbeddedId
    private TeamPk embeddedId;

    @MapsId("clubId")
    @ManyToOne(optional = false, fetch = FetchType.EAGER)
    @JoinColumn(name = "club_id", insertable = false, updatable = false)
    private Club club;

    ...
}

@Embeddable
public class TeamPk implements Serializable
{
    private static final long serialVersionUID = 1L;

    @Column(name = "club_id")
    private Integer clubId;

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

    @Column(name = "ordinal_nbr")
    private Integer ordinalNbr;

    ...
}

例外：

Caused by: Exception [EclipseLink-28019] (Eclipse Persistence Services - 2.7.7.v20200504-69f2c2b80d): org.eclipse.persistence.exceptions.EntityManagerSetupException
Exception Description: Deployment of PersistenceUnit [BBStatsPU] failed. Close all factories for this PersistenceUnit.
Internal Exception: Exception [EclipseLink-0] (Eclipse Persistence Services - 2.7.7.v20200504-69f2c2b80d): org.eclipse.persistence.exceptions.IntegrityException
Descriptor Exceptions: 
---------------------------------------------------------

Exception [EclipseLink-46] (Eclipse Persistence Services - 2.7.7.v20200504-69f2c2b80d): org.eclipse.persistence.exceptions.DescriptorException
Exception Description: There should be one non-read-only mapping defined for the primary key field [Teams.club_id].
Descriptor: RelationalDescriptor(net.bbstatstest.i265.entity.Team --> [DatabaseTable(Teams)])

Runtime Exceptions: 
---------------------------------------------------------

    at org.eclipse.persistence.exceptions.EntityManagerSetupException.deployFailed(EntityManagerSetupException.java:241)
    ... 182 more
Caused by: Exception [EclipseLink-0] (Eclipse Persistence Services - 2.7.7.v20200504-69f2c2b80d): org.eclipse.persistence.exceptions.IntegrityException
Descriptor Exceptions: 
---------------------------------------------------------

Exception [EclipseLink-46] (Eclipse Persistence Services - 2.7.7.v20200504-69f2c2b80d): org.eclipse.persistence.exceptions.DescriptorException
Exception Description: There should be one non-read-only mapping defined for the primary key field [Teams.club_id].
Descriptor: RelationalDescriptor(net.bbstatstest.i265.entity.Team --> [DatabaseTable(Teams)])

Runtime Exceptions: 
---------------------------------------------------------

    at org.eclipse.persistence.internal.sessions.DatabaseSessionImpl.initializeDescriptors(DatabaseSessionImpl.java:762)
    at org.eclipse.persistence.internal.sessions.DatabaseSessionImpl.initializeDescriptors(DatabaseSessionImpl.java:698)
    at org.eclipse.persistence.internal.sessions.DatabaseSessionImpl.initializeDescriptors(DatabaseSessionImpl.java:629)
    at org.eclipse.persistence.internal.sessions.DatabaseSessionImpl.postConnectDatasource(DatabaseSessionImpl.java:868)
    at org.eclipse.persistence.internal.sessions.DatabaseSessionImpl.loginAndDetectDatasource(DatabaseSessionImpl.java:811)
    at org.eclipse.persistence.internal.jpa.EntityManagerFactoryProvider.login(EntityManagerFactoryProvider.java:256)
    at org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.deploy(EntityManagerSetupImpl.java:772)
    ... 180 more

EclipseLink 抱怨 Teams.club_id 的列映射：

There should be one non-read-only mapping defined for the primary key field [Teams.club_id].

但是为什么呢？

嵌入的 ID 字段或更确切地说是 ID 类在 clubId 字段上具有 @Column 而没有 insertable = true, updatable = true，因此它默认为可写，至少这是文档所说的：https://javaee.github.io/javaee-spec/javadocs/javax/persistence/Column.html#insertable--

因此，所有其他 club_id 映射必须为 insertable = true, updatable = true 才能为只读，例如 Team.club 关系。

问题：

这里有什么问题？

请注意，当在 Team.club 和 TeamPk.clubId 之间切换 insertable = ..., updatable = ... 时，整个事情都会起作用。

为什么 EclipseLink 在这里阻塞？对我来说似乎是一个错误。

PS：我使用的是 EclipseLink 2.7.7。 （hibernate标签只是为了吸引更多关注）

Answer 1

通过将@MapsId("clubId") 放在关联上，您是在说“clubId 是否不提供自己的映射。相反，这里应该使用此属性上的映射来映射clubId 属性'。

这意味着当持久化实体时，Eclipselink 将使用Team.club 的 id 来填充 club_id 连接列，然后，它将使用该连接列的值来填充 Java 属性 Team.embeddedId.clubId，每当获取/刷新实体时。 您在Team.embeddedId.clubId 上放置的任何映射都将被忽略。

这个错误来自于 Eclipselink 不认为club_id 被映射两次。相反，只考虑Team.club 上的映射。作为主键属性的唯一映射，它可能不是insertable = false, updatable = false。

解决方法很简单：

1. 如果您希望Team.club 控制club_id 列的值，请删除insertable = false, updatable = false
2. 相反，如果您希望Team.embeddedId.clubId 控制club_id，则完全放弃@MapsId