我想通过 JPA 映射 Map<Long, List<POJO>>

Question

我想在 @Entity 类中映射一个 Map<Long, List<ItemAttribute>>，其中 ItemAttribute 本身是一个单独定义的 @Entity。

这是我用于映射的代码：

@Entity
@Table(name = "ITEM_ATTRIBUTE_GROUP")
public class ItemAttributeGroup implements Cloneable, Serializable
{
      @ElementCollection
      @MapKeyColumn(name="groupId")
      @JoinTable(name = "ATTRIBUTES_IN_GROUP", joinColumns = @JoinColumn(name = "groupId"),
                        inverseJoinColumns = @JoinColumn(name = "ID"))
      private Map<Long, List<ItemAttribute>> attributes = new HashMap<Long, List<ItemAttribute>>();
     //getters and setters........
}

ItemAttribute 是下面提到的一个单独的类：

@Entity
@Table(name = "ITEM_ATTRIBUTE")
public class ItemAttribute implements Cloneable, Serializable {
    private static final long serialVersionUID = -8017036630979138942L;

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

    @ElementCollection // this is a collection of primitives
    @JoinTable(name="ATTRIBUTE_VALUE_RANGE", joinColumns=@JoinColumn(name="ID"))
    @MapKeyColumn (name="RANGE_ID")// column name for map "key"
    @Column(name="VALUE")//  column name for map "value"
    private Map<String, String> attributeValueRange = new HashMap<String, String>();

    @ElementCollection // this is a collection of primitives
    @JoinTable(name="QUALIFIER_VALUE_RANGE", joinColumns=@JoinColumn(name="ID"))
    @MapKeyColumn (name="RANGE_ID")// column name for map "key"
    @Column(name="VALUE")//  column name for map "value"
    private Map<String, String> qualifierValueRange = new HashMap<String, String>();

    public Map<String, String> getAttributeValueRange() {
        return attributeValueRange;
    }

    public void setAttributeValueRange(Map<String, String> attributeValueRange) {
        this.attributeValueRange = attributeValueRange;
    }

    public Map<String, String> getQualifierValueRange() {
        return qualifierValueRange;
    }

    public void setQualifierValueRange(Map<String, String> qualifierValueRange) {
        this.qualifierValueRange = qualifierValueRange;
    }
}

问题出在我无法识别的代码中。 我收到此错误

使用@JoinTable.inverseJoinColumns 定位未映射的类： ItemAttributeGroup.attributes[java.util.List]

Answer 1

你需要创建一个中间类ItemAttributes。

@Entity
public class ItemAttributes {

   @OneToMany
   private List<ItemAttribute> attributes;
}

@Entity
public class ItemAttributeGroup implements Cloneable, Serializable {

   @OneToMany
   private Map<Long, ItemAttributes> attributesMap;
}