【IT168技术文档】 
    目前很多人使用Hibernate作为持久层，如果我们已经写了配置文件poweracl.hbm.xml，则不必再费劲写SQL的DDL。除了利用工具SchemaExport之外，还可以编写程序来自动初始化数据库，并且生成SQL DDL。 

    (1)Hibernate配置文件hibernate.cfg.xml

<?xml version='1.0' encoding='gb2312'?>
<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD//EN"
  "http://hibernate.sourceforge.net/hibernate-configuration-2.0.dtd">

<hibernate-configuration>
   <session-factory>
    <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
    <property name="hibernate.connection.url">jdbc:mysql://localhost/hibtest</property>
    <property name="hibernate.connection.username">test</property>
    <property name="hibernate.connection.password">123456</property>
    <property name="hibernate.connection.pool.size">20</property>
    <property name="hibernate.show_sql">true</property>
      <property name="jdbc.fetch_size">50</property>
      <property name="jdbc.batch_size">25</property>
      <property name="jdbc.use_scrollable_resultset">false</property>
    <property name="hibernate.dialect">net.sf.hibernate.dialect.MySQLDialect</property>

    <!-- Mapping files -->
      <mapping resource="com/hibtest/poweracl.hbm.xml"/>
   </session-factory>
</hibernate-configuration>

    注意：

    （1）JDBC驱动为com.mysql.jdbc.Driver，可以根据所使用的库而更换。 

    （2）dialect为数据库方言，根据所使用数据库不同而不同。这里是Mysql。 

    （3）jdbc.fetch_size和jdbc.batch_size过小会降低性能，这里是建议设置。 

    （4）mapping文件根据文件所在路径而不同。这里是放在WEB-INF/classes/com/hibtest/目录下。 

    (2)数据库映射配置poweracl.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN"
                                   "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">

<hibernate-mapping>
  <class name="com.hibtest.user" table="user" discriminator-value="W">
     <id name="loginname" type="string" >
          <column name="loginname" sql-type="char(16)" not-null="true"/>
            <generator class="assigned"/>
   </id>
   <property name="password" type="string">
        <column name="password" sql-type="varchar(20)" />
     </property>
        <property name="name" type="string">
        <column name="name" sql-type="varchar(20)" />
     </property>
        <property name="email" type="string">
        <column name="email" sql-type="varchar(60)" />
     </property>
        <property name="modified" type="date">
        <column name="modifier" />
     </property>
        <property name="creater" type="date">
        <column name="creater" />
     </property>
        <property name="lastlogin" type="date">
        <column name="lastlogin" />
     </property>
  </class>
</hibernate-mapping>

    说明：具体的poweracl.hbm.xml要根据数据库表而设置，这里只是列举一个user表。 

    (3) 初始化数据库类

package com.hibtest;

import net.sf.hibernate.HibernateException;
import net.sf.hibernate.Session;
import net.sf.hibernate.SessionFactory;
import net.sf.hibernate.Transaction;
import net.sf.hibernate.cfg.Configuration;
import net.sf.hibernate.tool.hbm2ddl.SchemaExport;

import java.io.File;
import java.util.HashSet;
import java.util.Set;

/**//**
 * <p/> vedadou
 * Date: 2004-02-25
 * Time: 9:40:15
 */
public class InitDB ...{
    static Session session;

    public static void main(String[] args) ...{
        Configuration config = null;
        Transaction tx = null;

        try ...{
            config = new Configuration().configure(new File("hibernate.cfg.xml"));
            System.out.println("Creating tables...");
            SchemaExport schemaExport = new SchemaExport(config);
            schemaExport.create(true, true);
            System.out.println("Table created.");
            SessionFactory sessionFactory = config.buildSessionFactory();
            session = sessionFactory.openSession();
            tx = session.beginTransaction();
            tx.commit();

        } catch (HibernateException e) ...{
            e.printStackTrace();
            try ...{
                tx.rollback();
            } catch (HibernateException e1) ...{
                e1.printStackTrace();
            }
        } finally ...{

        }
    }
}

    注意：在初始化之前，应该先手工创建一个空数据库，然后再执行InitDB程序create database hibtest