JPA / Hibernate嵌入式ID

好的，我们等着瞧

您有一个@AssociationOverride注释，其API指出：

此批注用于 覆盖 实体关系的属性或字段 的多对一或一对一 映射。

和

它可以应用于 扩展映射超类的实体， 以覆盖该映射超类定义的多对一或一对一映射

我没有在您的问题中没有看到@ManyToOne和@OnoToOne。因此，您的问题出了点问题。

但是我已经在您的StackTrace中看到以下日志

从报表引用报表的外键列号错误。应该是2

您有一个 由@EmbeddedId批注定义 的复合主键 ，该批注具有两个属性（fileName和xmlContent）

现在，让我们看看您的@CollectionOfElements

@CollectionOfElements(fetch=FetchType.EAGER)@JoinTable(name="t_reports",     // Your mistake goes here    joinColumns=@JoinColumn(name="log_report"))@Fetch(FetchMode.SELECT)private List<ReportingFile> reports;

它的外键仅包含 一个属性， 而您的复合主键包含 两个属性 。 两者必须匹配 。它解释了为什么您看到此好消息

从报表引用报表的外键列号错误。应该是2

您正确的映射应如下所示

@CollectionOfElements(fetch=FetchType.EAGER)@JoinTable(name="t_reports",     joinColumns={        // The number of columns defined by our Compound primary key (2)        // must match the number of columns defined by its Foreign key (2)        @JoinColumn(name="file_name", referencedColumnName="file_name"),        @JoinColumn(name="xml_content", referencedColumnName="xml_content")})@Fetch(FetchMode.SELECT)private List<ReportingFile> reports;

还有更多：我不知道您的目标数据库是否支持Clob作为主键。因此请记住这一点。

根据您的回复添加到原始答案

1º 第一种情况（ 不带 @CollectionOfElements）

@Entitypublic class Reporting {    // You said you just want a single fileName as primary key    @Id    @Column(name="file_name", nullable=false)    private String fileName;    // You said you still want to have the whole ReportingFile object    @Embedded    private ReportingFile reportingFile;    @Embeddable    public static class ReportingFile implements Serializable {        // You must set up insertable=false, updatable=false        @Column(name="file_name", insertable=false, updatable=false)        private String fileName;        @Column(name="xml_content")        private Clob xmlContent;   }}

请记住以下几点：Hibernate 不允许您定义两个属性，它们都共享同一列 。因此，我必须在fileName属性中定义insertable =
false，updatable = false。

当我执行以下操作时

Reporting reporting = new Reporting();reporting.setFileName("home.pdf");ReportingFile reportingFile = new ReportingFile();// It will not persisted because of insertable=false, updatable=falsereportingFile.setFileName("home.pdf");reportingFile.setXmlContent(someClobObject);session.save(reporting); // It works

2º 第一种情况（ 带有 @CollectionOfElements）

@Entitypublic class Reporting {    // You said you just want a single fileName as primary key    @Id    @Column(name="file_name", nullable=false)    private String fileName;    // You said you still want to have the whole ReportingFile object    @Embedded    private ReportingFile reportingFile;    @CollectionOfElements(fetch=FetchType.EAGER)    @JoinTable(        name="t_reports",        joinColumns=@JoinColumn(name="file_name", referencedColumnName="file_name", insertable=false, updatable=false))    private List<ReportingFile> reports;    @Embeddable    public static class ReportingFile implements Serializable {        // You must set up insertable=false, updatable=false        @Column(name="file_name", insertable=false, updatable=false)        private String fileName;        @Column(name="xml_content")        private Clob xmlContent;   }}

当我执行以下操作时

Reporting reporting = new Reporting();reporting.setFileName("home.pdf");ReportingFile reportingFile = new ReportingFile();// It will not persisted because of insertable=false, updatable=falsereportingFile.setFileName("home.pdf");reportingFile.setXmlContent(someClobObject);reporting.getReports().add(reportingFile);session.save(reporting); // It does not work

hibernate会抱怨

映射中用于收集的重复列：报告列：file_name

因此，当您有一个@CollectionOfElements共享一个外键时， 它将无法按预期工作 。但是您可以采取解决方法

@Entitypublic class Reporting {    // You said you just want a single fileName as primary key    @Id    @Column(name="file_name", nullable=false)    private String fileName;    // You said you still want to have the whole ReportingFile object    @Embedded    private ReportingFile reportingFile;    // Your workaround goes here    @CollectionOfElements(fetch=FetchType.EAGER)    @JoinTable(        name="t_reports",        joinColumns=@JoinColumn(name="file_name", referencedColumnName="file_name"))    private List<Clob> xmlContents;    @Transient    public List<ReportingFile> getReports() {        List<ReportingFile> reports = new ArrayList<ReportingFile>();        for(Clob xmlContent: getXmlContents()) reports.add(new ReportingFile(getFileName(), xmlContent));        return reports;    }    @Embeddable    public static class ReportingFile implements Serializable {        // required no-arg  constructor        public ReportingFile() {}        public ReportingFile(String fileName, Clob xmlContent) { this.fileName = fileName; this.xmlContent = xmlContent;        }        // You must set up insertable=false, updatable=false        @Column(name="file_name", insertable=false, updatable=false)        private String fileName;        @Column(name="xml_content")        private Clob xmlContent;   }}

请注意，在自己的类内部使用时，可以将@Embeddable类定义为静态类。