JPA（Hibernate、EclipseLink）映射：为什么这段代码不起作用（使用 JPA 2.0、@EmbeddedId 复合 PK-FK 的 2 个关系链）？

Question

我有三张桌子：

CREATE TABLE PostAddresses
(
  contact_id INTEGER NOT NULL,
  ordinal_nbr SMALLINT NOT NULL,
  PRIMARY KEY (contact_id, ordinal_nbr)
);

CREATE TABLE Foos
(
  contact_id INTEGER NOT NULL,
  ordinal_nbr SMALLINT NOT NULL,
  PRIMARY KEY (contact_id, ordinal_nbr),
  FOREIGN KEY (contact_id, ordinal_nbr) REFERENCES PostAddresses (contact_id, ordinal_nbr)
);

CREATE TABLE Bars
(
  contact_id INTEGER NOT NULL,
  ordinal_nbr SMALLINT NOT NULL,
  numba INTEGER NOT NULL,
  PRIMARY KEY (contact_id, ordinal_nbr, numba),
  FOREIGN KEY (contact_id, ordinal_nbr) REFERENCES Foos (contact_id, ordinal_nbr)
);

简单的逻辑：Bars -> Foos -> PostAddresses all by (contact_id, ordinal_nbr)，不管是什么意思。

这里是六个实体和各自的组合键类。

@Entity
@Table(name = "PostAddresses")
public class PostAddress implements Serializable
{
    @EmbeddedId
    private PostAddressId embeddedId;

    ...
}

@Embeddable
public class PostAddressId implements Serializable
{
    @Column(name = "contact_id")
    private Integer contactId;

    @Column(name = "ordinal_nbr")
    private Integer ordinalNbr = 1;

    ...
}

@Entity
@Table(name = "Foos")
public class Foo implements Serializable
{
    @EmbeddedId
    private FooId embeddedId;

    @MapsId(value = "postAddressId")
    @OneToOne
    @JoinColumns(value = {@JoinColumn(name = "contact_id", referencedColumnName = "contact_id"), @JoinColumn(name = "ordinal_nbr", referencedColumnName = "ordinal_nbr")})
    private PostAddress postAddress = null;

    ...
}

@Embeddable
public class FooId implements Serializable
{
    @Embedded
    private PostAddressId postAddressId; //just one field!

    ...
}

@Entity
@Table(name = "Bars")
public class Bar implements Serializable
{
    @EmbeddedId
    private BarId embeddedId;

    ...
}

@Embeddable
public class BarId implements Serializable
{
    @Embedded
    private FooId fooId;

    @Column(name = "numba")
    private Integer numba;

    ...
}

其实没什么特别的，Bar 引用 Foo，Foo 引用 PostAddress，都是通过复合键类。由于外键是组合的并且是 PK 的一部分，因此我必须将 ID 类嵌套到 ID 类中。我认为这是正确的。但是，我使用 Hibernate 3.6 和 EclipseLink 2.2.0 得到以下堆栈跟踪

休眠：

org.hibernate.AssertionFailure: Unexpected nested component on the referenced entity when mapping a @MapsId: tld.transmuc.model.Foo
    at org.hibernate.cfg.CopyIdentifierComponentSecondPass.doSecondPass(CopyIdentifierComponentSecondPass.java:101)
    at org.hibernate.cfg.Configuration.processSecondPassesOfType(Configuration.java:1424)
    at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1388)
    at org.hibernate.cfg.Configuration.buildMappings(Configuration.java:1345)
    at org.hibernate.ejb.Ejb3Configuration.buildMappings(Ejb3Configuration.java:1477)
    at org.hibernate.ejb.EventListenerConfigurator.configure(EventListenerConfigurator.java:193)
    at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:1096)
    at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:278)
    at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:362)
    at org.hibernate.ejb.HibernatePersistence.createEntityManagerFactory(HibernatePersistence.java:56)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:48)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:32)
    at tld.transmuc.Main.main(Main.java:27)
Exception in thread "main" javax.persistence.PersistenceException: [PersistenceUnit: transmuc] Unable to configure EntityManagerFactory
    at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:374)
    at org.hibernate.ejb.HibernatePersistence.createEntityManagerFactory(HibernatePersistence.java:56)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:48)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:32)
    at tld.transmuc.Main.main(Main.java:27)
Caused by: org.hibernate.AssertionFailure: Unexpected nested component on the referenced entity when mapping a @MapsId: tld.transmuc.model.Foo
    at org.hibernate.cfg.CopyIdentifierComponentSecondPass.doSecondPass(CopyIdentifierComponentSecondPass.java:101)
    at org.hibernate.cfg.Configuration.processSecondPassesOfType(Configuration.java:1424)
    at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1388)
    at org.hibernate.cfg.Configuration.buildMappings(Configuration.java:1345)
    at org.hibernate.ejb.Ejb3Configuration.buildMappings(Ejb3Configuration.java:1477)
    at org.hibernate.ejb.EventListenerConfigurator.configure(EventListenerConfigurator.java:193)
    at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:1096)
    at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:278)
    at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:362)
    ... 4 more

Eclipse 链接：

Exception in thread "main" Local Exception Stack: 
Exception [EclipseLink-30005] (Eclipse Persistence Services - 2.2.0.v20101118-r8514): org.eclipse.persistence.exceptions.PersistenceUnitLoadingException
Exception Description: An exception was thrown while searching for persistence archives with ClassLoader: sun.misc.Launcher$AppClassLoader@1f7182c1
Internal Exception: javax.persistence.PersistenceException: Exception [EclipseLink-28018] (Eclipse Persistence Services - 2.2.0.v20101118-r8514): org.eclipse.persistence.exceptions.EntityManagerSetupException
Exception Description: Predeployment of PersistenceUnit [transmuc] failed.
Internal Exception: java.lang.NullPointerException
    at org.eclipse.persistence.exceptions.PersistenceUnitLoadingException.exceptionSearchingForPersistenceResources(PersistenceUnitLoadingException.java:126)
    at org.eclipse.persistence.jpa.PersistenceProvider.createEntityManagerFactory(PersistenceProvider.java:136)
    at org.eclipse.persistence.jpa.PersistenceProvider.createEntityManagerFactory(PersistenceProvider.java:65)
    at javax.persistence.Persistence.createEntityManagerFactory(Unknown Source)
    at javax.persistence.Persistence.createEntityManagerFactory(Unknown Source)
    at tld.transmuc.Main.main(Main.java:27)
Caused by: javax.persistence.PersistenceException: Exception [EclipseLink-28018] (Eclipse Persistence Services - 2.2.0.v20101118-r8514): org.eclipse.persistence.exceptions.EntityManagerSetupException
Exception Description: Predeployment of PersistenceUnit [transmuc] failed.
Internal Exception: java.lang.NullPointerException
    at org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.predeploy(EntityManagerSetupImpl.java:1021)
    at org.eclipse.persistence.internal.jpa.deployment.JPAInitializer.callPredeploy(JPAInitializer.java:95)
    at org.eclipse.persistence.jpa.PersistenceProvider.createEntityManagerFactory(PersistenceProvider.java:127)
    ... 4 more
Caused by: Exception [EclipseLink-28018] (Eclipse Persistence Services - 2.2.0.v20101118-r8514): org.eclipse.persistence.exceptions.EntityManagerSetupException
Exception Description: Predeployment of PersistenceUnit [transmuc] failed.
Internal Exception: java.lang.NullPointerException
    at org.eclipse.persistence.exceptions.EntityManagerSetupException.predeployFailed(EntityManagerSetupException.java:210)
    ... 7 more
Caused by: java.lang.NullPointerException
    at org.eclipse.persistence.internal.jpa.metadata.accessors.mappings.EmbeddedIdAccessor.process(EmbeddedIdAccessor.java:189)
    at org.eclipse.persistence.internal.jpa.metadata.MetadataDescriptor.processMappingAccessors(MetadataDescriptor.java:1417)
    at org.eclipse.persistence.internal.jpa.metadata.accessors.classes.ClassAccessor.processMappingAccessors(ClassAccessor.java:1405)
    at org.eclipse.persistence.internal.jpa.metadata.accessors.classes.EntityAccessor.processMappingAccessors(EntityAccessor.java:1061)
    at org.eclipse.persistence.internal.jpa.metadata.accessors.classes.EntityAccessor.process(EntityAccessor.java:601)
    at org.eclipse.persistence.internal.jpa.metadata.MetadataProject.processStage2(MetadataProject.java:1464)
    at org.eclipse.persistence.internal.jpa.metadata.MetadataProcessor.processORMMetadata(MetadataProcessor.java:483)
    at org.eclipse.persistence.internal.jpa.deployment.PersistenceUnitProcessor.processORMetadata(PersistenceUnitProcessor.java:453)
    at org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.predeploy(EntityManagerSetupImpl.java:975)
    ... 6 more

EclipseLink 绝对没有提示我哪个类是有问题的。至少 Hibernate 告诉我 @MapsId 注释和 Foo 类的问题：

org.hibernate.AssertionFailure: Unexpected nested component on the referenced entity when mapping a @MapsId: tld.transmuc.model.Foo

这里有什么问题？

PS：我可以整理一个 SSCCE，请问您是否需要一个（JavaSE、HSQLDB、Ant、Hibernate 3.6）。

Answer 1

只需从引用依赖 EmbeddedId 的 EmbeddedId 类型中删除 @Embedded 注释即可解决您的问题。：

@可嵌入 公共类 FooId 实现 Serializable { // 没有注释。 私人 PostAddressId postAddressId; //只有一个字段！ ... } ... @MapsId(value = "postAddressId") @OneToOne @JoinColumns(value = {@JoinColumn(name = "contact_id", referencedColumnName = "contact_id"), @JoinColumn(name = "ordinal_nbr", referencedColumnName = "ordinal_nbr")}) 私人邮政地址 postAddress = null;

（编辑）：另一个问题是 FooId 的使用。不应使用此类。 Foo 实体的 ID 类是 PostAddressId，OneToOne“postAddress”应该简单地标记为@Id 而不是@MapsId。同样，BarId 不应定义 Embedded，但应直接引用 PostAddressId。引用 PostAddress 的 Bar Mapping 应使用 MapsId。

请针对可怕的异常提交一个针对 EclipseLink 的错误，如果删除 @Embedded 和编辑中的其他更新不能解决您的问题，请同时提交一个 EclipseLink 错误。