Java 多对多表中的多对多
我有一个表Orders,其中包含产品的列表。对于与特定订单相对应的每个产品,我需要存储一个地址列表,其中单个产品(每个订单,每个产品)应交付给Java 多对多表中的多对多,java,mysql,hibernate,jpa,many-to-many,Java,Mysql,Hibernate,Jpa,Many To Many,我有一个表Orders,其中包含产品的列表。对于与特定订单相对应的每个产品,我需要存储一个地址列表,其中单个产品(每个订单,每个产品)应交付给 +----------------+------------+ | Order_ID | Product_ID | +----------------+------------+ | 1 | 1000 | | 2 | 1000 | | 2 |
+----------------+------------+
| Order_ID | Product_ID |
+----------------+------------+
| 1 | 1000 |
| 2 | 1000 |
| 2 | 1001 |
+----------------+------------+
因此,我有一个关于订单和产品的多对多表,我需要将上表中的每个条目映射到地址列表。所以我需要像这样的东西
|PK|Order_ID |Product_ID |
| 1| 1 | 1000 |
| 2| 2 | 1000 |
| 3| 2 | 1001 |
要将上表中的条目映射到地址列表,我需要在上面的PK和地址ID(我的地址表的主键)上再创建一个多对多表
这里PK_Order_Product是上一个表主键(PK)上的外键
我使用JPA来持久化我的MYSQL数据库,如果我的设计是正确的,请帮助我编写一个代码片段。如何在Java中使用JPA注释来实现这一点,这实际上是一个值得研究和实验的好问题。有许多方法可以进行映射。提出更好的设计实际上取决于您的应用程序需求。但以下是我认为实施映射的有效方法: 我将为
订单
、产品
和地址
创建3个单独的实体
我们不会在两个实体之间实现通常的多对多关系,订单
和产品
,其中每一方都有另一方的集合。相反,我将创建另一个实体来表示Order
和Product
之间的关系,并将其命名为ProductOrder
。以下是它们之间关系的映射方式:
与Order
有一对多关系ProductOrder
与ProductOrder
有多对一关系Order
与产品
有一对多关系产品订单
与ProductOrder
有多对一关系Product
ProductOrder
的主键将由Order
的主键和Product
的主键组成-因此这将是一个复合键。因此,我们需要使用@IdClass
来映射复合键
现在,以下是在多对多关系中实现多对多的诀窍:
ProductOrder
与地址有多对多关系
参见上述各实体的示例代码:
订单实体
@Entity
@Table(name = "ORDERS")
public class Order {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "ORDER_ID")
private Long id;
private int quantity;
@OneToMany(mappedBy = "order")
private List<ProductOrder> productOrderList = new ArrayList<ProductOrder>();
...
}
@Entity
@Table(name="PRODUCT")
public class Product {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "PRODUCT_ID")
private Long id;
private String name;
@OneToMany(mappedBy = "product")
private List<ProductOrder> productOrderList = new ArrayList<ProductOrder>();
...
}
@Entity
@Table(name="ADDRESS")
public class Address {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "ADDRESS_ID")
private Long id;
private String state;
@ManyToMany(mappedBy = "addressList")
private List<ProductOrder> productOrderList = new ArrayList<ProductOrder>();
...
}
@Entity
@Table(name="PRODUCT_ORDER")
@IdClass(ProductOrderId.class)
public class ProductOrder {
@Id
@ManyToOne
@JoinColumn(name="ORDER_ID")
private Order order;
@Id
@ManyToOne
@JoinColumn(name="PRODUCT_ID")
private Product product;
@ManyToMany
@JoinTable(name="PRODUCT_ORDER_ADDRESS",
joinColumns={@JoinColumn(name="ORDER_ID", referencedColumnName="ORDER_ID"),
@JoinColumn(name="PRODUCT_ID", referencedColumnName="PRODUCT_ID")},
inverseJoinColumns=@JoinColumn(name="ADDRESS_ID", referencedColumnName="ADDRESS_ID"))
private List<Address> addressList = new ArrayList<Address>();
...
}
下面是创建实体并持久化它们的示例代码:
EntityManager em = emf.createEntityManager();
em.getTransaction().begin();
Order order = new Order();
order.setQuantity(10);
em.persist(order);
Product product = new Product();
product.setName("Coffee");
em.persist(product);
Address address = new Address();
address.setState("CA");
em.persist(address);
ProductOrder productOrder = new ProductOrder();
productOrder.setOrder(order);
productOrder.setProduct(product);
productOrder.getAddressList().add(address);
address.getProductOrderList().add(productOrder);
em.persist(productOrder);
em.getTransaction().commit();
以下是在MySQL数据库中如何生成架构:
Hibernate:
create table ADDRESS (
ADDRESS_ID bigint not null auto_increment,
state varchar(255),
primary key (ADDRESS_ID)
)
Hibernate:
create table ORDERS (
ORDER_ID bigint not null auto_increment,
quantity integer not null,
primary key (ORDER_ID)
)
Hibernate:
create table PRODUCT (
PRODUCT_ID bigint not null auto_increment,
name varchar(255),
primary key (PRODUCT_ID)
)
Hibernate:
create table PRODUCT_ORDER (
ORDER_ID bigint,
PRODUCT_ID bigint,
primary key (ORDER_ID, PRODUCT_ID)
)
Hibernate:
create table PRODUCT_ORDER_ADDRESS (
ORDER_ID bigint not null,
PRODUCT_ID bigint not null,
ADDRESS_ID bigint not null
)
Hibernate:
alter table PRODUCT_ORDER
add constraint FK_sl39bwx60xjbvoiujpaes74ty
foreign key (ORDER_ID)
references ORDERS (ORDER_ID)
Hibernate:
alter table PRODUCT_ORDER
add constraint FK_n0i7uxq6rxsc0mcred1cds4m9
foreign key (PRODUCT_ID)
references PRODUCT (PRODUCT_ID)
Hibernate:
alter table PRODUCT_ORDER_ADDRESS
add constraint FK_kad6crei9lgrv1nuuuff42vs8
foreign key (ADDRESS_ID)
references ADDRESS (ADDRESS_ID)
Hibernate:
alter table PRODUCT_ORDER_ADDRESS
add constraint FK_hpx0e467dvpqi5i6kxmujns2b
foreign key (ORDER_ID, PRODUCT_ID)
references PRODUCT_ORDER (ORDER_ID, PRODUCT_ID)
你的问题是什么?这个设计正确吗?能给我一个更好的设计吗。如果是,我如何使用JPAJPA实现这一点是围绕类设计的。发布您的类类顺序{long orderId;}我收到以下错误,原因是:org.hibernate.MappingException:在org.hibernate.mapping.Table(ADDRESS)及其相关的超表和辅助表中找不到逻辑名称为ADDRESS_ID的列。您能帮我解决这个问题吗@Entity@Table(name=“ADDRESS”)公共类地址实现了可序列化的,IEntity{private static final long serialVersionUID=1L;@Id@GeneratedValue(strategy=GenerationType.IDENTITY)@Column(name=“Address_Id”)private long pk;@Column(name=“Address_name”,nullable=false,length=255)private String addressName;}
是否使用hbm2ddl auto?是否设置为创建或更新?好的,请更新问题并发布所有实体的代码,以便我们可以看到所有映射(如果它们被正确声明)。注释部分中的张贴代码不可读。或者任何您认为更快共享信息的方法…上面提供的解决方案的复制粘贴是您提供的解决方案吗?
EntityManager em = emf.createEntityManager();
em.getTransaction().begin();
Order order = new Order();
order.setQuantity(10);
em.persist(order);
Product product = new Product();
product.setName("Coffee");
em.persist(product);
Address address = new Address();
address.setState("CA");
em.persist(address);
ProductOrder productOrder = new ProductOrder();
productOrder.setOrder(order);
productOrder.setProduct(product);
productOrder.getAddressList().add(address);
address.getProductOrderList().add(productOrder);
em.persist(productOrder);
em.getTransaction().commit();
Hibernate:
create table ADDRESS (
ADDRESS_ID bigint not null auto_increment,
state varchar(255),
primary key (ADDRESS_ID)
)
Hibernate:
create table ORDERS (
ORDER_ID bigint not null auto_increment,
quantity integer not null,
primary key (ORDER_ID)
)
Hibernate:
create table PRODUCT (
PRODUCT_ID bigint not null auto_increment,
name varchar(255),
primary key (PRODUCT_ID)
)
Hibernate:
create table PRODUCT_ORDER (
ORDER_ID bigint,
PRODUCT_ID bigint,
primary key (ORDER_ID, PRODUCT_ID)
)
Hibernate:
create table PRODUCT_ORDER_ADDRESS (
ORDER_ID bigint not null,
PRODUCT_ID bigint not null,
ADDRESS_ID bigint not null
)
Hibernate:
alter table PRODUCT_ORDER
add constraint FK_sl39bwx60xjbvoiujpaes74ty
foreign key (ORDER_ID)
references ORDERS (ORDER_ID)
Hibernate:
alter table PRODUCT_ORDER
add constraint FK_n0i7uxq6rxsc0mcred1cds4m9
foreign key (PRODUCT_ID)
references PRODUCT (PRODUCT_ID)
Hibernate:
alter table PRODUCT_ORDER_ADDRESS
add constraint FK_kad6crei9lgrv1nuuuff42vs8
foreign key (ADDRESS_ID)
references ADDRESS (ADDRESS_ID)
Hibernate:
alter table PRODUCT_ORDER_ADDRESS
add constraint FK_hpx0e467dvpqi5i6kxmujns2b
foreign key (ORDER_ID, PRODUCT_ID)
references PRODUCT_ORDER (ORDER_ID, PRODUCT_ID)