[英]JPA (Hibernate) mapping of Map. What annotations should I use for java.util.Map mapping?
表結構:
TABLE products (id (PK), name, price);
TABLE orders (id (PK), customer_id, user_id);
//product_quantity is quantity of product in particular order
TABLE products_to_orders (product_id, order_id, product_quantity
PRIMARY KEY (product_id, order_id),
FOREIGN KEY (product_id) REFERENCES products (id) ON DELETE CASCADE,
FOREIGN KEY (order_id) REFERENCES orders (id) ON DELETE CASCADE
);
這是我的Order.java
:
@Entity
@Table(name = "orders")
public class Order extends BaseEntity {
...
//this map holds Products and their quantities in order;
@ManyToMany(fetch = FetchType.EAGER)
@JoinTable(
name = "products_to_orders"
,joinColumns = @JoinColumn(name = "order_id")
,inverseJoinColumns = @JoinColumn(name = "product_id") //it seems that i don't need this line
)
@MapKeyJoinColumn(name = "product_id")
@Column(name = "product_quantity")
private Map<Product, Integer> productQuantityMap;
...
我使用這些注釋的映射不起作用。 它給出了一個例外:
原因:org.hibernate.AnnotationException:使用@OneToMany或@ManyToMany定位未映射的類:com.malikov.shopsystem.model.Order.productQuantityMap [java.lang.Integer]
因此,我無法管理如何正確注釋此地圖。 非常感謝您的幫助! 這是我在GitHub上的代表的鏈接https://github.com/malikov-yurii/online-shop-management-system.git
UPDATE。 有兩種正確的解決方案(來自Neil和Maciej):
Variation 1:
@ElementCollection(fetch = FetchType.EAGER)
@JoinTable(
name = "products_to_orders"
,joinColumns = @JoinColumn(name = "order_id")
)
@MapKeyJoinColumn(name = "product_id")
@Column(name = "product_quantity")
private Map<Product, Integer> productQuantityMap;
Variation 2
@ElementCollection(fetch = FetchType.EAGER)
@CollectionTable(name = "products_to_orders")
@MapKeyJoinColumn(name = "product_id")
@Column(name = "product_quantity")
private Map<Product, Integer> productQuantityMap;
您選擇的JPA提供程序的文檔中是否包括如何映射“地圖”字段? 您可以在DataNucleus JPA提供的本文檔中看到它的描述。 簡單來說,您需要包括
@ElementCollection
@JoinTable
Map<Product, Integer> productQuantityMap;
(以及要配置架構的所有其他注釋,但這是必不可少的)。
試試這個配置。 @ElementCollection代替@ManyToMany和@CollectionTable代替@JoinTable
@ElementCollection
@CollectionTable(name = "products_to_orders"
@MapKeyJoinColumn(name = "product_id")
@Column(name = "product_quantity")
private Map<Product, Integer> productQuantityMap;
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