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>
（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>
(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 ...{ } }}
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