Question

我有以下两个jpa hibernate实体，

@Entity
public class Product {

    @Id
    @GeneratedValue(generator = "uuid")
    @GenericGenerator(name="uuid", strategy="uuid2")
    private String id;

    @ManyToOne
    private Type type;

    @ManyToOne
    private Attribute attribute;
}

和

@Entity
public class ProductFamily {

    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(generator = "uuid")
    @GenericGenerator(name="uuid", strategy="uuid2")
    private String id;

    @ManyToMany
    @Formula("("
            + " SELECT t.id "
            + " FROM Type t "
            + " WHERE t.id IN ( "
            + "     SELECT p.type_id "
            + "     FROM product p"
            + "     WHERE p.family_id = id"
            + "     ) "
            + " order by t.value asc "
            + " )")
    private Set<Type> types;

    @ManyToMany()
    @Formula("("
            + " SELECT a.id "
            + " FROM Attribute a "
            + " WHERE a.id IN ( "
            + "     SELECT p.attribute_id "
            + "     FROM product p"
            + "     WHERE p.family_id = id"
            + "     ) "
            + " order by a.value asc "
            + " )")
    private Set<Attribute> attributes;

    @OneToMany(mappedBy="family")
    @LazyCollection(LazyCollectionOption.FALSE)
    private Set<Product> products;

}

我正在尝试在产品系列中生成类型和属性字段，作为家庭产品的类型和属性的集合。（注意，类型和属性类本身就是实体）

不允许使用以下公式，因为我得到以下内容

Caused by: javax.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.persistenceException(EntityManagerFactoryBuilderImpl.java:1225)
... 51 more
Caused by: org.hibernate.MappingException: Could not determine type for: java.util.Set, at table: ProductFamily, for columns: [org.hibernate.mapping.Formula( ( SELECT t.id  FROM Type t  WHERE t.id IN (   SELECT p.type_id    FROM product p      WHERE p.family_id = id  )  ) )]
at org.hibernate.mapping.SimpleValue.getType(SimpleValue.java:336)
... 56 more

这似乎表明将公式的结果映射到一组实体的问题

这可能与公式有关吗？如果是这样的话？

如果没有，有没有一种标准的方法来做这种事情？如果不是，你会建议做什么更好的方法。

最后，我希望尽可能使用jpa，但正如我正在研究公式我已经开放使用hibernate特定的解决方案

Answer 1

5年前，但对于今天读此书的人来说：

在@Formula附近，您应该添加： @ElementCollection(targetClass = X.class)，其中X是集合对象的类型。

如何使用hibernate或jpa生成动态的实体集合？

1 个答案: