hibernate - JPA + Hibernate 扩展表映射

Question

对于我们项目中的其中一项要求，我们遵循:

http://msdn.microsoft.com/en-us/library/aa479086.aspx#mlttntda_nvp管理多个租户。

表结构图片请引用上面的链接。

我需要帮助来管理映射。这是我的想法:

    @Entity
    @Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
    public abstract class AbstractEntity {
    @Id @GeneratedValue(strategy = GenerationType.TABLE)
    private Long id;

    @OneToMany(mappedBy="entities")
    private Set<ExtensionTable> extensionTable = new HashSet<ExtensionTable>();

    ....
}


@Entity
public class ExtensionTable {
    @Id @GeneratedValue
    private Long id;

    @ManyToOne
    private Set<AbstractEntity> entities = new HashSet<AbstractEntity>();

    ...
}

@Entity
public class Employee extends AbstractEntity {
    ...
}

我发现很难定义元数据表的映射。

Answer 1

来自规范 11.1.26:ManyToOne 注释定义与另一个具有多对一多重性的实体类的单值关联。 我认为您不能将 @ManyToOne 与 Set 一起使用。 我会尝试这样的事情:

@Entity
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS) // Depending on your provider, I generally use JOINED or SINGLE_TABLE
public abstract class AbstractEntity {
    @Id @GeneratedValue(strategy = GenerationType.TABLE)
    private Long id;

    @OneToMany(mappedBy="entity")
    private Set<ExtensionTable> extensionTable = new HashSet<ExtensionTable>();

    ....
}


@Entity
public class ExtensionTable {
    @Id @GeneratedValue
    private Long id;

    @ManyToOne
    private AbstractEntity entity;

    @ManyToOne
    private Metadata metadata;    

    @Column
    private String value;

    ...
}

@Entity
public class Metadata {
    @Id @GeneratedValue
    private Long id;

    @ManyToOne
    private AbstractEntity entity;

    @Column
    private String extLabel;        

    @Column
    private String extDataType; // So, here is a problem, you'll have to find an efficient way to deal with the data type.
    ...
}

@Entity
public class Employee extends AbstractEntity {
    ...
}