Hibernate添加指定用户与订单的关系 请帮忙

我的entity.xml文件user.xml<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="cn.com.ambow.ects.entity">
<class name="User" table="user">
<id name="id" column="user_id">
<generator class="native">
</generator>
</id>
<property name="name" column="name" type="string"></property>
<property name="passwd" column="passwd"></property> <one-to-one name="info" class="ContcatInfo" cascade="all"></one-to-one>
<set name="order" cascade="all" inverse="true" >
<key column="user_id"></key>
<one-to-many class="Order" />
</set>
</class></hibernate-mapping>order.xml<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="cn.com.ambow.ects.entity">
<class name="Order" table="myorder">
<id name="id" column="order_id">
<generator class="native">
</generator>
</id>
<property name="name"></property>
<property name="cost"></property>
<many-to-one name="user" class="User" column="user_id"
cascade="all" fetch="join" ></many-to-one>
<set name="orderlines" cascade="all" inverse="true">
<key column="order_id"></key>
<one-to-many class="OrderLine" />
</set> <many-to-one name="status" class="OrderStatus" column="orderStatus_id"></many-to-one>
<many-to-one name="payWay" class="PayWay" column="payWay_id"></many-to-one>
<!--
<set name="product" table="product_order"> <key
column="order_id"></key> <many-to-many class="Product"
column="product_id"></many-to-many> </set>
-->
</class>
</hibernate-mapping>
orderImpl code 
public void addOrder(User user) throws ManagerOrderException {
Session session = null; Transaction tran = null; try {
// 获得session
session = HibernateUtil.getSession();
// 开始事务
tran = session.beginTransaction();
// do some work
session.save(user);
// 提交事务
tran.commit();
} catch (Exception e) {
e.printStackTrace();
tran.rollback(); }
}测试代码 public class UserOrderTest { public static void main(String[] args) { User user = new User();
user.setId(1);
Order order = new Order();
order.setName("sh");
order.setCost(300);
order.setUser(user);
user.getOrder().add(order);
OrderDao orderdao = new OrderDaoImpl();
orderdao.addOrder(user);
｝
｝问题：添加进去的时候 并不是我设置用户的id ，用户的id是自动增长的