说明：一个客户可以对应多个订单。以此为例说明用myeclipse如何来实现这个应用，看看myeclipse是如何做的，生成配置文件质量如何。
环境：
开发工具：myeclipse 5.5.1 GA
数 据 库：mysql-5.0.37
操作系统：windows xp professional 中文版
步骤：
1、建立mysql5数据库testdb，脚本下面已经给出。
2、配置myeclipse的数据库服务器，并建立名称为mysql5的数据库链接。
3、建议myeclipse的web工程，名称为dx_d2y，并加入hibernate支持，选择hibernate3.1，最高就支持到3.1。
4、在myeclipse的数据库视图中链接数据库并通过表生成实体PO和配置文件，中间不生成DAO。
5、检查配置文件的正确性，然后测试类进行测试。
一、建立数据库的脚本:
alter table orders drop foreign key fk_order_customer;
drop table if exists customers;
drop table if exists orders;
create table customers (
id bigint not null,
name varchar(15),
primary key (id)
);
create table orders (
id bigint not null,
order_number varchar(15),
customer_id bigint not null,
primary key (id)
);
alter table orders add index fk_order_customer(customer_id), add constraint fk_order_customer
foreign key (customer_id) references customers (id);
foreign key (customer_id) references customers (id);
表关系的逻辑图：
+-----------+ +--------------+
| customers | | oreders |
+-----------+ +--------------+
| ID |<------| | ID |
| NAME | | | ORDER_NUMBER |
+-----------+ |------------| CUSTOMER_ID |
+--------------+
特别注意：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，关闭了自动提交模式，也就是SET
AUTOCOMMIT=0。
AUTOCOMMIT=0。
my.ini
------------------------------------
#[WinMySQLAdmin]
#Server=D:/mysql-5.0.37-win32/bin/mysqld.exe
[mysqld]
# set basedir to your installation path
#basedir=D:/mysql-5.0.37-win32
# set datadir to the location of your data directory
port = 3306
key_buffer = 16K
max_allowed_packet = 1M
table_cache = 4
sort_buffer_size = 64K
read_buffer_size = 256K
read_rnd_buffer_size = 256K
net_buffer_length = 2K
thread_stack = 64K
datadir=data
default-character-set=gbk
init_connect='SET AUTOCOMMIT=0'
default-table-type=InnoDB
init_connect='set completion_type=1'
[client]
default-character-set=gbk
------------------------------------
二、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;
// Constructors
/** default constructor */
public Customers() {
}
/** full constructor */
public Customers(String name) {
this.name = name;
}
// 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;
}
}
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>
</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">
<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">
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>
三、写测试类进行测试：
---------------------
package org.lavasoft;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.Transaction;
public class Test {
/**
* @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();
tx=session.beginTransaction();
Customers c=new Customers("c1");
Orders o1 =new Orders();
o1.setOrderNumber("11");
Orders o2 =new Orders();
o2.setOrderNumber("22");
o1.setCustomers(c);
o2.setCustomers(c);
try {
session.save(o1);
session.save(o2);
tx.commit();
} catch (HibernateException e) {
// TODO Auto-generated catch block
e.printStackTrace();
tx.rollback();
}finally{
session.close();
}
}
}
四、运行测试类Test，控制台打印信息：
------------------------------------------
Hibernate: select max(ID) from orders
Hibernate: select max(ID) from customers
Hibernate: insert into customers (NAME, ID) values (?, ?)
Hibernate: insert into orders (CUSTOMER_ID, ORDER_NUMBER, ID) values (?, ?, ?)
Hibernate: insert into orders (CUSTOMER_ID, ORDER_NUMBER, ID) values (?, ?, ?)
查看数据库：
------------------------------------------
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 10
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> describe customers;
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| ID | bigint(20) | NO | PRI | | |
| NAME | varchar(15) | YES | | NULL | |
+-------+-------------+------+-----+---------+-------+
2 rows in set (0.00 sec)
mysql> describe orders;
+--------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------------+-------------+------+-----+---------+-------+
| ID | bigint(20) | NO | PRI | | |
| ORDER_NUMBER | varchar(15) | YES | | NULL | |
| CUSTOMER_ID | bigint(20) | NO | MUL | | |
+--------------+-------------+------+-----+---------+-------+
3 rows in set (0.01 sec)
mysql> select * from customers;
+----+------+
| ID | NAME |
+----+------+
| 1 | c1 |
+----+------+
1 row in set (0.00 sec)
mysql> select * from orders;
+----+--------------+-------------+
| ID | ORDER_NUMBER | CUSTOMER_ID |
+----+--------------+-------------+
| 1 | 11 | 1 |
| 2 | 22 | 1 |
+----+--------------+-------------+
2 rows in set (0.00 sec)
mysql>
总结：从上面过程可以看出，myeclipse实现这个单向多对一的过程非常的简单，虽然是自动生成的SessionFactory和hibernate.cfg.xml但是没有一点问题。这就省去了大量的工作量。并且生成的映射文件和实体Bean（也叫PO，有很多叫法）质量也不错，基本上不需要什么改动。在此实现过程中，需要改动地方有：
1、生成的指定数据库testdb要删除掉，因为连接字符串里面有。
2、在orders.hbm.xml中默认不会自动设置级联保存和更新，可以自己加上cascade="save-update"。
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