Hibernate技巧（1）：利用配置文件編寫程序生成數(shù)據(jù)庫

2019-11-18 13:56:15

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目前很多人使用Hibernate作為持久層，假如我們已經(jīng)寫了配置文件poweracl.hbm.xml，則不必再費(fèi)勁寫SQL的DDL。除了利用工具SchemaEXPort之外，還可以編寫程序來自動初始化數(shù)據(jù)庫，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>
    <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 resource="com/hibtest/poweracl.hbm.xml"/>
   </session-factory>
</hibernate-configuration>

注重：（1）JDBC驅(qū)動為com.mysql.jdbc.Driver，可以根據(jù)所使用的庫而更換。
            （2）dialect為數(shù)據(jù)庫方言，根據(jù)所使用數(shù)據(jù)庫不同而不同。這里是Mysql。
            （3）jdbc.fetch_size和jdbc.batch_size過小會降低性能，這里是建議設(shè)置。
            （4）mapping文件根據(jù)文件所在路徑而不同。這里是放在WEB-INF/classes/com/hibtest/目錄下。

(2)數(shù)據(jù)庫映射配置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>

說明：具體的poweracl.hbm.xml要根據(jù)數(shù)據(jù)庫表而設(shè)置，這里只是列舉一個user表。

(3) 初始化數(shù)據(jù)庫類

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 {

        }
    }
}

注重：在初始化之前，應(yīng)該先手工創(chuàng)建一個空數(shù)據(jù)庫，然后再執(zhí)行InitDB程序
   create database hibtest

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