环境、数据库还和上篇文章的一样。只是表中的数据清空了。
注意：对于有外键的表，清空数据有两种方法：第一是先drop掉外键约束后，进行清除。第二种是先清除从表数据（orders），然后清除主表的数据（customers），具体我及不说了，有空我在写写数据库外键约束的方面的文章，这点也很重要的。
步骤
1、清除orders、customers两表数据。
2、用myeclipse新建web工程sx_d2y，加入hibernate支持。
3、同时选中orders、customers生成实体Bean和mapping文件，并对mapping做小的改动。
4、写两个测试类，分别保存Orders对象和Customers的实体对象，看看能否保存到数据库中。
废话不说了，看过程吧！
一、通过myeclipse生成实体和配置文件：
Customers.java
---------------------
public class Customers implements java.io.Serializable {
// Fields
private Long id;
private String name;
private Set orderses = new HashSet(0);
// Constructors
/** default constructor */
public Customers() {
}
/** full constructor */
public Customers(String name, Set orderses) {
this.name = name;
this.orderses = orderses;
}
// Property accessors
public Long getId() {
return this.id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
public Set getOrderses() {
return this.orderses;
}
public void setOrderses(Set orderses) {
this.orderses = orderses;
}
}
Orders.java
---------------------
public class Orders implements java.io.Serializable {
// Fields
private Long id;
private Customers customers;
private String orderNumber;
// Constructors
/** default constructor */
public Orders() {
}
/** minimal constructor */
public Orders(Customers customers) {
this.customers = customers;
}
/** full constructor */
public Orders(Customers customers, String orderNumber) {
this.customers = customers;
this.orderNumber = orderNumber;
}
// Property accessors
public Long getId() {
return this.id;
}
public void setId(Long id) {
this.id = id;
}
public Customers getCustomers() {
return this.customers;
}
public void setCustomers(Customers customers) {
this.customers = customers;
}
public String getOrderNumber() {
return this.orderNumber;
}
public void setOrderNumber(String orderNumber) {
this.orderNumber = orderNumber;
}
}
Customers.hbm.xml
-------------------
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
<!--
Mapping file autogenerated by MyEclipse Persistence Tools
-->
<hibernate-mapping>
<class name="org.lavasoft.Customers" table="customers">
<id name="id" type="java.lang.Long">
<column name="ID" />
<generator class="increment" />
</id>
<property name="name" type="java.lang.String">
<column name="NAME" length="15" />
</property>
<set name="orderses" inverse="true" cascade="all-delete-orphan">
<key>
<column name="CUSTOMER_ID" not-null="true" />
</key>
<one-to-many class="org.lavasoft.Orders" />
</set>
</class>
</hibernate-mapping>
Orders.hbm.xml
-------------------
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
<!--
Mapping file autogenerated by MyEclipse Persistence Tools
-->
<hibernate-mapping>
<class name="org.lavasoft.Orders" table="orders" catalog="testdb">
<id name="id" type="java.lang.Long">
<column name="ID" />
<generator class="increment" />
</id>
<many-to-one name="customers" class="org.lavasoft.Customers" fetch="select" cascade="save-update">
<column name="CUSTOMER_ID" not-null="true" />
</many-to-one>
<property name="orderNumber" type="java.lang.String">
<column name="ORDER_NUMBER" length="15" />
</property>
</class>
</hibernate-mapping>
二、写测试类进行测试
在测试之前，先清空这两个关联表的数据。
D:\mysql-5.0.37-win32\bin>mysql -uroot -pleizhimin
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 32
Server version: 5.0.37-community MySQL Community Edition (GPL)
Type 'help;' or '\h' for help. Type '\c' to clear the buffer.
mysql> use testdb;
Database changed
mysql> show tables;
+------------------+
| Tables_in_testdb |
+------------------+
| card |
| customers |
| orders |
| person |
| t_user |
| user |
+------------------+
6 rows in set (0.00 sec)
mysql> delete from orders;
Query OK, 2 rows affected (0.03 sec)
mysql> delete from customers;
Query OK, 1 row affected (0.03 sec)
看清了，我已经干掉这个两个表的所有数据了。
然后，我写一个测试类TestbyOrder，从保存Orders实体对象，看能否级联保存相关的Customers对象：
package org.lavasoft;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.Transaction;
public class TestbyOrder {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
if(HibernateSessionFactory.getSession()==null)System.out.println("null");
Session session=HibernateSessionFactory.getSession();
Transaction tx=session.beginTransaction();
Customers c=new Customers();
c.setName("c1");
Orders o1 =new Orders();
o1.setOrderNumber("11");
Orders o2 =new Orders();
o2.setOrderNumber("22");
c.getOrderses().add(o1);
c.getOrderses().add(o2);
o1.setCustomers(c);
o2.setCustomers(c);
try {
session.save(o1);
session.save(o2);
//session.save(c);
tx.commit();
} catch (HibernateException e) {
// TODO Auto-generated catch block
e.printStackTrace();
tx.rollback();
}finally{
session.close();
}
}
}
运行这个类，控制台信息如下：
Hibernate: select max(ID) from orders
Hibernate: select max(ID) from customers
Hibernate: insert into customers (NAME, ID) values (?, ?)
Hibernate: insert into testdb.orders (CUSTOMER_ID, ORDER_NUMBER, ID) values (?, ?, ?)
Hibernate: insert into testdb.orders (CUSTOMER_ID, ORDER_NUMBER, ID) values (?, ?, ?)
从控制台信息发现已经级联保存进去了。
在从开库看看，到底写的进去的数据是什么：
mysql> select * from orders;
+----+--------------+-------------+
| ID | ORDER_NUMBER | CUSTOMER_ID |
+----+--------------+-------------+
| 1 | 11 | 1 |
| 2 | 22 | 1 |
+----+--------------+-------------+
2 rows in set (0.00 sec)
mysql> select * from customers;
+----+------+
| ID | NAME |
+----+------+
| 1 | c1 |
+----+------+
1 row in set (0.00 sec)
mysql>
开库查结果表明，写入Orders对象的同时，写入了相关的Customers对象。
下面再进行一下反向测试：
先清空两个表
mysql> delete from orders;
Query OK, 2 rows affected (0.03 sec)
mysql> delete from customers;
Query OK, 1 row affected (0.00 sec)
mysql>
然后写测试类：
package org.lavasoft;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.Transaction;
public class TestbyCustomer {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
if(HibernateSessionFactory.getSession()==null)System.out.println("null");
Session session=HibernateSessionFactory.getSession();
Transaction tx=session.beginTransaction();
Customers c=new Customers();
c.setName("c1");
Orders o1 =new Orders();
o1.setOrderNumber("11");
Orders o2 =new Orders();
o2.setOrderNumber("22");
c.getOrderses().add(o1);
c.getOrderses().add(o2);
o1.setCustomers(c);
o2.setCustomers(c);
try {
session.save(c);
tx.commit();
} catch (HibernateException e) {
// TODO Auto-generated catch block
e.printStackTrace();
tx.rollback();
}finally{
session.close();
}
}
}
运行这个测试类，控制台信息如下：
Hibernate: select max(ID) from customers
Hibernate: select max(ID) from orders
Hibernate: insert into customers (NAME, ID) values (?, ?)
Hibernate: insert into testdb.orders (CUSTOMER_ID, ORDER_NUMBER, ID) values (?, ?, ?)
Hibernate: insert into testdb.orders (CUSTOMER_ID, ORDER_NUMBER, ID) values (?, ?, ?)
开库查，看看写入数据是什么:
mysql> select * from orders;
+----+--------------+-------------+
| ID | ORDER_NUMBER | CUSTOMER_ID |
+----+--------------+-------------+
| 1 | 11 | 1 |
| 2 | 22 | 1 |
+----+--------------+-------------+
2 rows in set (0.00 sec)
mysql> select * from customers;
+----+------+
| ID | NAME |
+----+------+
| 1 | c1 |
+----+------+
1 row in set (0.00 sec)
mysql>
开库查结果表明，写入Customers对象的同时，写入了相关的Orders对象。
从而可以证明：这个双向关联是成功的。
呵呵，myeclipse不错，是个好东西。
本文转自 leizhimin 51CTO博客，原文链接：http://blog.51cto.com/lavasoft/30164，如需转载请自行联系原作者
