myeclipse試用小記----Hibernate多對一雙向關聯(2)

在上篇文章“myeclipse試用小記----Hibernate多對一單向關聯(1)”中，講到了“Hibernate多對一單向關聯”，現在我打算把這個做成雙向的，也就是多對一雙向關聯，看看myeclipse是如何實現的。

環境、數據庫還和上篇文章的一樣。只是表中的數據清空了。

注意：對于有外鍵的表，清空數據有兩種方法：第一是先drop掉外鍵約束后，進行清除。第二種是先清除從表數據(orders)，然后清除主表的數據(customers)，具體我及不說了，有空我在寫寫數據庫外鍵約束的方面的文章，這點也很重要的。

步驟

1、清除orders、customers兩表數據。

2、用myeclipse新建web工程sx_d2y，加入hibernate支持。

3、同時選中orders、customers生成實體Bean和mapping文件，并對mapping做小的改動。

4、寫兩個測試類，分別保存Orders對象和Customers的實體對象，看看能否保存到數據庫中。

廢話不說了，看過程吧！

一、通過myeclipse生成實體和配置文件：

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

-------------------

/p>

"[url]http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd[/url]">

Orders.hbm.xml

-------------------

/p>

"[url]http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd[/url]">

二、寫測試類進行測試

在測試之前，先清空這兩個關聯表的數據。

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，我已經干掉這個兩個表的所有數據了。

然后，我寫一個測試類TestbyOrder，從保存Orders實體對象，看能否級聯保存相關的Customers對象：

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();

}

}

}

運行這個類，控制臺信息如下：

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 (?, ?, ?)

從控制臺信息發現已經級聯保存進去了。

在從開庫看看，到底寫的進去的數據是什么：

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>

開庫查結果表明，寫入Orders對象的同時，寫入了相關的Customers對象。

下面再進行一下反向測試：

先清空兩個表

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>

然后寫測試類：

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();

}

}

}

運行這個測試類，控制臺信息如下：

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 (?, ?, ?)

開庫查，看看寫入數據是什么:

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>

開庫查結果表明，寫入Customers對象的同時，寫入了相關的Orders對象。

從而可以證明：這個雙向關聯是成功的。

呵呵，myeclipse不錯，是個好東西。

myeclipse試用小記----Hibernate多對一單向關聯(1)

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