1.1 在一个网上商城里有订单表，商品表，那么一个订单内能够有多个商品，一个商品能够被多个订单拥有。订单与商品就造成了多对多的关系，那么咱们如何将这个关系经过hibernate映射到数据库呢？java
1.2 解决思路，hibernate为咱们提供了，多对多的映射,web
<set ...>
<many-to-many>
</set>
这个方法的确可行，可是经过这个方法咱们的中间表并不能操做其余数据，如订单记录中还有着数量以及购买单价字段，那么咱们没法操做这些字段。数据库
1.3 经过将多对多，转换为两个一对多的映射完成需求，并为中间表创建对应的实体。session
2.1 商品实体类app
package com.lab9.domain;
import java.util.HashSet;
import java.util.Set;
public class Product {
Integer id;
String name;
double price;
String description;
Set<OrderItem> orderitems = new HashSet<OrderItem>();
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public double getPrice() {
return price;
}
public void setPrice(double price) {
this.price = price;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public Set<OrderItem> getOrderitems() {
return orderitems;
}
public void setOrderitems(Set<OrderItem> orderitems) {
this.orderitems = orderitems;
}
}
2.2 订单实体dom
package com.lab9.domain;
import java.util.HashSet;
import java.util.Set;
public class Order {
private Integer id;
double total;
String realname;
String phone;
String address;
String postcode;
Set<OrderItem> orderitems = new HashSet<OrderItem>();
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public double getTotal() {
return total;
}
public void setTotal(double total) {
this.total = total;
}
public String getRealname() {
return realname;
}
public void setRealname(String realname) {
this.realname = realname;
}
public String getPhone() {
return phone;
}
public void setPhone(String phone) {
this.phone = phone;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
public String getPostcode() {
return postcode;
}
public void setPostcode(String postcode) {
this.postcode = postcode;
}
public Set<OrderItem> getOrderitems() {
return orderitems;
}
public void setOrderitems(Set<OrderItem> orderitems) {
this.orderitems = orderitems;
}
}
2.3 中间表（记录订单，商品，购买数量，购买单价）svg
package com.lab9.domain;
public class OrderItem {
Integer id;
Order order;
Product product;
int quantity;
double purchase;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public Order getOrder() {
return order;
}
public void setOrder(Order order) {
this.order = order;
}
public Product getProduct() {
return product;
}
public void setProduct(Product product) {
this.product = product;
}
public int getQuantity() {
return quantity;
}
public void setQuantity(int quantity) {
this.quantity = quantity;
}
public double getPurchase() {
return purchase;
}
public void setPurchase(double purchase) {
this.purchase = purchase;
}
}
2.4 映射文件post
<!---product.hbm.xml--->
<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.lab9.domain">
<class name="Product" table="product">
<id name="id" column="id" type="integer">
<generator class="native"></generator>
</id>
<property name="name" type="string" length="16" not-null="true" column="name"></property>
<property name="price" type="double" column="price"></property>
<property name="description" type="string" length="16" column="description"></property>
<!-- 一对多 -->
<set name="orderitems" table="orderitem">
<key column="product_id"></key>
<one-to-many class="OrderItem"/>
</set>
</class>
</hibernate-mapping>
<!---order.hbm.xml--->
<hibernate-mapping package="com.lab9.domain">
<class name="Order" table="orders">
<id name="id" column="id" type="integer">
<generator class="native"></generator>
</id>
<property name="total" type="double" not-null="true" column="total"></property>
<property name="realname" type="string" length="8" column="realname"></property>
<property name="phone" type="string" length="16" column="phone"></property>
<property name="address" type="string" length="16" column="address"></property>
<property name="postcode" type="string" length="6" column="postcode"></property>
<!-- 一对多 -->
<set name="orderitems" table="orderitem">
<key column="order_id"></key>
<one-to-many class="OrderItem"/>
</set>
</class>
</hibernate-mapping>
<!---orderitem.hbm.xml--->
<hibernate-mapping package="com.lab9.domain">
<class name="OrderItem" table="orderitem">
<id name="id" column="id" type="integer">
<generator class="native"></generator>
</id>
<many-to-one name="order" class="Order" column="order_id"></many-to-one>
<many-to-one name="product" class="Product" column="product_id" fetch="join"></many-to-one>
<property name="quantity" type="integer" column="quantity" not-null="true"></property>
<property name="purchase" type="double" column="purchase" not-null="true"></property>
</class>
</hibernate-mapping>
2.5测试类测试
public class Client {
private static SessionFactory sf;
private static Session session;
public static void main(String[] args) {
StandardServiceRegistry registy = new StandardServiceRegistryBuilder().configure().build();
sf = new MetadataSources(registy).buildMetadata().buildSessionFactory();
session = sf.openSession();
Transaction tx = session.beginTransaction();
//订单一
Order order = new Order();
order.setTotal(1000);
order.setAddress("华软");
order.setRealname("李浩然");
order.setPostcode("510990");
order.setPhone("87818998");
//订单二
Order order2 = new Order();
order2.setTotal(5000);
order2.setAddress("中大");
order2.setRealname("李明");
order2.setPostcode("510000");
order2.setPhone("38008781");
//产品1
Product pro = new Product();
pro.setName("thinkpad电脑");
pro.setDescription("thinkpad");
pro.setPrice(6780);
//产品2
Product p2 = new Product();
p2.setName("彩电");
p2.setDescription("性价比高");
p2.setPrice(200);
//产品3
Product p3 = new Product();
p3.setName("tcl彩电");
p3.setPrice(3600);
p3.setDescription("tcl彩电");
//订单记录
OrderItem item1 = new OrderItem();
OrderItem item2 = new OrderItem();
OrderItem item3 = new OrderItem();
OrderItem item4 = new OrderItem();
//一个订单有多条商品记录
item1.setOrder(order);
item1.setProduct(pro);
item1.setQuantity(100);
item1.setPurchase(6000);
item2.setOrder(order);
item2.setProduct(p2);
item2.setQuantity(200);
item2.setPurchase(3000);
order.getOrderitems().add(item1);
order.getOrderitems().add(item2);
//一个商品有多条商品记录
item3.setOrder(order2);
item3.setProduct(p3);
item3.setQuantity(30);
item3.setPurchase(3300);
item4.setOrder(order2);
item4.setProduct(pro);
item4.setQuantity(60);
item4.setPurchase(6200);
order2.getOrderitems().add(item3);
order2.getOrderitems().add(item4);
try
{
//保存记录
session.save(order);
session.save(pro);
session.save(p2);
session.save(item1);
session.save(item2);
session.save(order2);
session.save(p3);
session.save(item3);
session.save(item4);
//查询
Order myOrder = (Order)session.get(Order.class, 9);
if(myOrder != null)
{
int costMoney = 0;
for(OrderItem item:myOrder.getOrderitems())
{
costMoney += (item.getQuantity()*item.getPurchase());
}
System.out.println("订单号:"+myOrder.getId());
System.out.println("总花费:"+costMoney+"\n"+"购买了如下商品：");
for(OrderItem item:myOrder.getOrderitems())
{
System.out.println("商品名:"+item.getProduct().getName());
}
}
tx.commit();
}
catch(Exception e)
{
e.printStackTrace();
tx.rollback();
}
session.close();
}
}