Question

我有下表...

Object1
-------
id
...

Object2
-------
id
...

AttributeValue      
--------------      
id                  
attribute_id        
object_id  
value         

Attribute    
---------    
id           
name         
type

...和实体类

@Entity
@Table(name = "Attribute")
public class Attribute {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id")
    private Long id;

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

    @Column(name = "type")
    private String type;
}


@Entity
@Table(name = "AttributeValue")
public class AttributeValue {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id")
    private Long id;

    @Column(name = "attribute_id")
    private Long attributeId;

    @Column(name = "object_id")
    private Long objectId;

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


@Entity
@Table(name = "Object1")
public class Object1 {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    // ...    

    // how to annotate to get all matching attribute values?
    private Set<AttributeValue> values;
}

我想让休眠状态的values实例变量充满所有具有相应AttributeValue和属性类型object_id的{{1}}。

如果只是关于object1的标准，我会写例如。

object_id

但是在这种情况下，它还将填写类型为@JoinColumn(insertable = false, updatable = false, name = "object_id") private Set<AttributeValue> values;等的值。

所以我的问题是：这种语义是否可以在Hibernate中表达？如果可以，如何表达？

编辑：我想强调一下，目标是要有多个没有共同层次结构的对象（这里是object2，Object1，... Object2），但都共享具有属性的功能。所有对象的属性将驻留在 one 表中，该表由某种区分符（此处示例为ObjectN）加以区分。

Answer 1

我认为该对象必须是：

@Entity
@Table(name = "AttributeValue")
public class AttributeValue {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id")
    private Long id;

    @Column(name = "attribute_id")
    private Long attributeId;

    @ManyToOne
    @JoinColumn(name="object_id", nullable=false)
    private Object1 object1;

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


@Entity
@Table(name = "Object1")
public class Object1 {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @OneToMany(mappedBy="object1")
    private Set<AttributeValue> values;
}

休眠将仅在AttributeValue表上生成object_id列。

休眠：如何使用第三个表将属性与条件联接

1 个答案: