Hibernate实体层次设计(二)

Table per concrete class方式:

TItem有两个子类：TBook、TDVD。按照Table per concrete class方式，每个字类对应一张数据库表。对应于TBook和TDVD，我们有以下库表：

1.数据库库表
T_Book.sql

DROP TABLE T_Book;

CREATE TABLE T_Book (
        id INT NOT NULL AUTO_INCREMENT
      , name VARCHAR ( 50 )
      , manufacturer VARCHAR ( 50 )
      , pagecount INT
      , PRIMARY KEY (id)
);

T_DVD.sql

DROP TABLE T_DVD;

CREATE TABLE T_DVD (
        id INT NOT NULL AUTO_INCREMENT
      , name VARCHAR(50)
      , manufacturer VARCHAR(50)
      , regioncode VARCHAR(30)
      , PRIMARY KEY (id)
);

2.配置文件
配置文件和普通配置文件没有区别

TBook.hbm.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.blogjava.start">
    <class name="TBook" table="T_Book" catalog="sample">
        <id name="id" column="id" type="java.lang.Integer">
            <generator class="native" />
        </id>

        <property name="name" type="java.lang.String" column="name"/>
        <property name="manufacturer" type="java.lang.String" column="manufacturer"/>        
        <property name="pageCount" type="java.lang.Integer" column="pagecount"/>        
    </class>
</hibernate-mapping>

TDVD.hbm.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.blogjava.start">
    <class name="TDVD" table="T_DVD" catalog="sample">
        <id name="id" column="id" type="java.lang.Integer">
            <generator class="native" />
        </id>

        <property name="name" type="java.lang.String" column="name"/>
        <property name="manufacturer" type="java.lang.String" column="manufacturer"/>        
        <property name="regionCode" type="java.lang.String" column="regioncode"/>        
    </class>
</hibernate-mapping>

3.测试代码
HibernateTest.java
package cn.blogjava.start;

import java.util.Iterator;
import java.util.List;

import junit.framework.Assert;
import junit.framework.TestCase;

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;


public class HibernateTest extends TestCase {
    
     Session session = null;
    /**
      * JUnit中的setUp方法在TestCase初始化的时候会自动调用
      * 一般用于初始化公用资源
     */
    protected void setUp() {
        try {
            /**
              * 可以采用hibernate.properties或者hibernate.cfg.xml
              * 配置文件的初始化代码
              *
              * 采用hibernate.properties
              * Configuration config = new Configuration()；
              * config.addClass(TUser.class);
             */
            
            //采用hibernate.cfg.xml配置文件，与上面的方法对比，两个差异
            //1.Configuration的初始化方式
            //2.xml
             Configuration config = new Configuration().configure();
             SessionFactory sessionFactory = config.buildSessionFactory();
             session = sessionFactory.openSession();
            
         } catch (HibernateException e) {
            // TODO: handle exception
             e.printStackTrace();
         }        
     }

    /**
      * JUnit中的tearDown方法在TestCase执行完毕的时候会自动调用
      * 一般用于释放资源
     */    
    protected void tearDown() {
        try {
             session.close();        
         } catch (HibernateException e) {
            // TODO: handle exception
             e.printStackTrace();
         }        
     }    
    
    /**
      * 对象持久化测试(Insert方法)
     */        
    public void testInsert() {
         Transaction tran = null;
        try {
             tran = session.beginTransaction();
             TBook book1 = new TBook();
            
             book1.setManufacturer("电子工业");
             book1.setName("Java beginner");
             book1.setPageCount(501);
            
             TBook book2 = new TBook();
             book2.setManufacturer("机械工业");
             book2.setName("Thinking in java");
             book2.setPageCount(1201);
            
             TDVD dvd1 = new TDVD();
             dvd1.setManufacturer("columnibia");
             dvd1.setName("Lord king");
             dvd1.setRegionCode("5 area");
            
             TDVD dvd2 = new TDVD();
             dvd2.setManufacturer("sony");
             dvd2.setName("Forrest gump");
             dvd2.setRegionCode("3 area");            

             session.save(book1);
             session.save(book2);
             session.save(dvd1);
             session.save(dvd2);
             session.flush();
             tran.commit();
             Assert.assertEquals(book1.getId().intValue()>0, true);
             Assert.assertEquals(book2.getId().intValue()>0, true);
             Assert.assertEquals(dvd1.getId().intValue()>0, true);
             Assert.assertEquals(dvd2.getId().intValue()>0, true);
         } catch (HibernateException e) {
            // TODO: handle exception
             e.printStackTrace();
             Assert.fail(e.getMessage());
            if(tran != null) {
                try {
                     tran.rollback();
                 } catch (Exception e1) {
                    // TODO: handle exception
                     e1.printStackTrace();
                 }
             }
         }
     }
    
    /**
      * 对象读取测试(Select方法)
     */            
    public void testSelect(){

         //指定了具体父类，如果是from TItem，是会失败的。
         List list = session.createQuery(" from cn.blogjava.start.TItem").list();
        
         Iterator it = list.iterator();
        while (it.hasNext()) {
             TItem item = (TItem)it.next();
             System.out.println(item.getName());
            
         }
     }
}