hibernate关系映射----多对一单向关联
一个客户可以对应多个订单。
表结构：两张表使用powerdesiner设计生成，产生引用错误。
出现问题：1.定义的级联关系只安一中方式生成，即双向的所以删除了parent表的set属性，同时删除映射文件的set集合，
2.没有定义级联关系cascade属性
drop table if exists Customer1;
drop table if exists OrderC1;
/*==============================================================*/
/* Table: Customer1 */
/*==============================================================*/
create table Customer1
(
id int not null auto_increment,
name varchar(20),
primary key (id)
)
type = InnoDB;
/*==============================================================*/
/* Table: OrderC1 */
/*==============================================================*/
create table OrderC1
(
id int not null,
order_id varchar(20),
customer_id int not null,
primary key (id)
)
type = InnoDB;
alter table OrderC1 add constraint FK_Reference_1111 foreign key (customer_id)
references Customer1 (id) on delete restrict on update restrict;
注意：因为有外键约束，需要事务支持，在安装数据库的时候，需要配置mysql数据库服务器的参数。数据库的引擎应该用InnoDB
二、通过myeclipse生成实体和配置文件：
package many_one;
@SuppressWarnings("serial")
public class Customer1 implements java.io.Serializable {
private Integer id;
private String name;
public Customer1() {
}
public Customer1(String name ) {
this.name = name;
}
public Integer getId() {
return this.id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
}
@SuppressWarnings("serial")
public class Orderc1 implements java.io.Serializable {
private Integer id;
private Customer1 customer1;
private String orderId;
public Orderc1() {
}
public Orderc1(Customer1 customer1) {
this.customer1 = customer1;
}
public Orderc1(Customer1 customer1, String orderId) {
this.customer1 = customer1;
this.orderId = orderId;
}
public Integer getId() {
return this.id;
}
public void setId(Integer id) {
this.id = id;
}
public Customer1 getCustomer1() {
return this.customer1;
}
public void setCustomer1(Customer1 customer1) {
this.customer1 = customer1;
}
public String getOrderId() {
return this.orderId;
}
public void setOrderId(String orderId) {
this.orderId = orderId;
}
}
配置文件
Customer1.hbm.xml
<hibernate-mapping>
<class name="many_one.Customer1" table="customer1" catalog="test1" >
<id name="id" type="integer" >
<column name="id" not-null="false"/>
<generator class="increment" />
</id>
<property name="name" type="string">
<column name="name" length="20" />
</property>
</class>
</hibernate-mapping>
Orderc1.hbm.xml
<hibernate-mapping>
<class name="many_one.Orderc1" table="orderc1" catalog="test1">
<id name="id" type="integer">
<column name="id" />
<generator class="increment" />
</id>
<many-to-one name="customer1" class="many_one.Customer1" fetch="select" cascade="save-update">
<column name="customer_id" not-null="true" />
</many-to-one>
<property name="orderId" type="string">
<column name="order_id" length="20" />
</property>
</class>
</hibernate-mapping>
package many_one;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
public class tests {
/**
* @param args
*/
public static void main(String[] args) {
Configuration cfg = new Configuration().configure();
SessionFactory sf =cfg.buildSessionFactory();
Session session =sf.openSession();
Transaction ts = session.beginTransaction();
Customer1 c = new Customer1("c1");
Orderc1 o = new Orderc1();
o.setOrderId("23");
o.setCustomer1(c);
session.save(o);
ts.commit();
}
}