类型，属性，实例和值之间的关系

我正在开发一个通过Hibernate在数据库中存储数据的Java应用程序。

I'm developing an Java-application which stores its data via Hibernate in a database.

此应用程序的一个功能是定义类型等模板。用于重用。例如，该类型具有属性，您可以创建一个具有属性值的类型实例。

One feature of this application is to define templates like types, etc. for reuse. For instance the type has attributes and you can create instances of an type, which has values for the attributes.

问题是，我不知道如何确保只能为属性分配哪个类型定义的值。在我的解决方案中，有一个冗余导致问题，但我不知道如何删除它。

The problem is, that I don't know how to ensure that only values for attributes can assigned which the type defines. In my solution there is a redundancy which cause the problem, but I don't know how to remove it.

我当前（和有问题的）方法看起来像这样： / p>

My current (and problematic) approach looks like this:

@Entity
class Type
{
    @Id
    @Generated
    private Long id;

    @OneToMany(mappedBy="type")
    private List<Attribute> attributes;

    //...
}

@Entity
class Attribute
{
    @Id
    @Generated
    private Long id;

    @ManyToOne
    private Type type;

    //...
}

@Entity
class Instance
{
    @Id
    @Generated
    private Long id;

    @ManyToOne
    private Type type;

    //...
}

@Entity
class AttributeValue
{

    @Id
    @Embedded
    private ResourceAttributValueId id;

    @Column(name="val")
    private String value;

    //...
}

@Embeddable
public class ResourceAttributValueId implements Serializable
{
    @ManyToOne
    private ResourceStateImpl resource;

    @ManyToOne
    private ResourceAttributeImpl attribute;

    //...
}

有定义类型是冗余的：可以通过AttributeValue-> Attribute-> Type和AttributeValue-> Instance-> Type

There the definition of the type is redundant: Type can be reached via AttributeValue->Attribute->Type and AttributeValue->Instance->Type

访问类型另一个想法是使用类型+属性名称作为属性的id和实例+属性名称作为属性值的id，但这不能解决我的问题。

Another idea was to use type + attribute name as id of the attribute and instance + attribute name as id of the attribute value, but that doesn't solves my problem.