数据库的设计及hibernate实体映射
以《商品案例数据库为例》
首先
商品案例数据库设计：
管理员表：
??????? id???? ：递增序列
??????? name? ：管理员
??????? pass?? ：密码
客户表
??????? id???? ：递增序列
??????? name? ：登录名称
??????? pass?? ：登录密码
??????? sex??? ： 性别??????? //enum
??????? email? ：注册邮箱???
??????? rdate?? ：注册日期??? //BeanUtils
??????? state?? ：是否被激活的状态? 0 1
商品表
??????? id???? ：递增序列
??????? name? ： 商品的名称
??????? type?? ： 商品的类型
??????? price?? ：商品的价格
订单表：
??????? Id???????? ：递增序列
??????? number??? ：订单编号
? customerid? ：客户名称
??????? odate????? ：订单时间
??????? state?????? ：订单的状态 //已发货? 未发货? 0 1
??????? ostate????? ：确认订单是否订购???????????? 0 1
??? 订单明细表
??????? id
??????? goodid?? ：商品的名称
??????? num???? ：商品数量
??????? total???? ：商品的总价格
??????? ordersid? ：订单
一张订单可以有多个商品，一个商品可以有多个订单
所以：订单表和商品表是多对多的关系
一个顾客可以有多个订单，一个订单只能属于一个顾客
所以：顾客表和订单表是一对多的关系
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要实现Hibernate实体映射首先要导入hibernate所需要的包
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接下来用hibernate的映射实现数据表的生成
首先先生成管理员表
代码如下：
public class Admin implements Serializable{
?????? private static final long serialVersionUID = 1L;
?????? private int id;
?????? private String name;
?????? private String pass;
?????? public Admin() {}
?????? public Admin(String name, String pass) {
?????????? this.name = name;
?????????? this.pass = pass;
?????? }
????? 省略 Get，set方法
}
映射文件中的代码：
<hibernate-mapping>
?????? <class name="cn.csdn.domain.Admin" table="admins" catalog="db">
???????????? <id name="id">
???????????? <generator type="string" length="30"/>
???????????? <property name="pass" type="string" length="12"/>
?????? </class>
</hibernate-mapping>
接下来生成顾客表和订单表
?????? 顾客表：顾客表和订单表是一对多的关系
public class Customer implements Serializable {
??? private static final long serialVersionUID = 1L;
??? private int id;
??? private String name;
??? private String pass;
??? private Sex sex; //enum
??? private String email;
??? private Date rdate; //BeanUtils
??? private int state;
??? private Set<Orders> orders = new HashSet<Orders>();
??? public Customer(String name, String pass, Sex sex, String email,
?????????? Date rdate, int state, Set<Orders> orders) {
?????? this.name = name;
?????? this.pass = pass;
?????? this.sex = sex;
?????? this.email = email;
?????? this.rdate = rdate;
?????? this.state = state;
?????? this.orders = orders;
??? }
??? public Customer() {}
省略 Get，set方法
}
映射文件中的代码：
? <class name="cn.csdn.domain.Customer" table="customers" catalog="db">
?????? <id name="id">
????????? <generator type="string" length="30" />
?????? <property name="pass" type="string" length="12" />
?????? <property name="sex" type="string" length="4" />
?????? <property name="email" type="string" length="30" />
?????? <property name="rdate" type="timestamp" />
?????? <property name="state" type="integer" />
???? <set name="orders" table="orders">
?????????? <key column="cid" />//cid是订单表的外键，顾客表的主键
?????????? <one-to-many />
???? </set>
??? </class>
订单表：
顾客表和订单表是一对多的关系；
??????? 订单表和商品表是多对多的关系，所以要加一个表，变成两一对多的实体映射
??????? 订单表和订单明细表是一对多的关系，商品表和订单明细表是一对多的关系
所以就加了一个订单明细表
public class Orders implements Serializable{
??? private static final long serialVersionUID = 1L;
??? private int id;
??? private String number;
??? private Customer customer;
??? private Date odate;
??? private int state;
??? private int Qstate;
??? private Set<OrdersItem> ordersItem = new HashSet<OrdersItem>();
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??? public Orders() { }
??? public Orders(int id, String number, Customer customer, Date odate,
?????????? int state, int qstate, Set<OrdersItem> ordersItem) {
?????? this.id = id;
?????? this.number = number;
?????? this.customer = customer;
?????? this.odate = odate;
?????? this.state = state;
?????? Qstate = qstate;
?????? this.ordersItem = ordersItem;
??? }
省略 Get，set方法
}
映射文件中的代码：
<class name="cn.csdn.domain.Orders" table="orders" catalog="db">
?????? <id name="id">
????????? <generator type="string" length="30"/>
?<many-to-one name="customer"
column="cid"/>
//订单表和顾客表是多对一的关系
?????? <property name="odate" type="timestamp" />
?????? <property name="state" type="integer" />
?????? <property name="Qstate" type="integer" />
?????? <set name="ordersItem">
???????? <key column="oid"/>//订单明细表中的oid外键是订单表的主键
???????? <one-to-many table="goods" catalog="db">
?????? <id name="id">
????????? <generator type="string" length="50"/>
?????? <property name="type" type="string" length="40"/>
?????? <property name="price" type="double"/>
?????? <set name="ordersItem">
???????? <key column="gid"/>
???????? <one-to-many table="ordersItems"
?????? catalog="db">
?????? <id name="id">
?????????? <generator />
?????? </id>
<many-to-one name="goods" />
?????? <property name="num" type="integer" />
?????? <property name="total" type="double" />
?????? <many-to-one name="orders" />
</class>
总结：一方主键做多方外键，一方用set集合多方用一方对象
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