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 ------------------- <?xml version="1.0" encoding="utf-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "[url]http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd[/url]"> <!-- 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" "[url]http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd[/url]"> <!-- 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、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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