标签：hibernate

这是一个Hibernate文档中的简单例子，环境是Tomcat+MySql+Hibernate

下载了Tomcat5.0，安装……

下载了Hibernate2，解包……

下载了MySql-nt5.0，安装……

下载数据库驱动mysql-connector-java-3.0.15-ga，解包……

数据库连接池配置：把数据库驱动mysql-connector-java-3.0.15-ga-bin.jar拷贝到%Tomcat%\common\lib下，在%Tomcat%\conf\server.xml里找到<Host>……</Host>，在其间添加

<Context path="/mytest" docBase="mytest" debug="0" reloadable="true" crossContext="true">

<Resource name="jdbc/mysql" auth="Container" type="javax.sql.DataSource"/>

<ResourceParams name="jdbc/mysql">

<parameter>

<name>factory</name>

<value>org.apache.commons.dbcp.BasicDataSourceFactory</value>

</parameter>

<!-- MySQL dB username and password for dB connections -->

<parameter>

<name>username</name>

<value>root</value>

</parameter>

<parameter>

<name>password</name>

<value>root</value>

</parameter>

<parameter>

<name>driverClassName</name>

<value>org.gjt.mm.mysql.Driver</value>

</parameter>

<parameter>

<name>url</name>

<value>jdbc:mysql://localhost:3306/test</value>

</parameter>

<parameter>

<name>maxActive</name>

<value>100</value>

</parameter>

<parameter>

<name>maxIdle</name>

<value>30</value>

</parameter>

<parameter>

<name>maxWait</name>

<value>10000</value>

</parameter>

</ResourceParams>

</Context>

解释：Context里的path是应用程序的路径，就是%tomcat%\webapps下的目录。

然后配置Hibernate：

在%tomcat%\webapps下建一个mytest目录，以及相应的WEB-INF、classes、lib目录，将Hibernate2.jar拷到lib下，将Hibernate解包后的lib目录下需要用到的包也拷过去：

cglib-full-2.0.2.jar

commons-collections-2.1.1.jar

commons-logging-1.0.4.jar

dom4j-1.4.jar

ehcache-0.9.jar

jta.jar

log4j-1.2.8.jar

odmg-3.0.jar

log4j还有一个properties文件要拷到classes目录下

在WEB-INF下的web.xml里添加数据库连接池的设置

<web-app>

<resource-ref>

<description>DB Connection</description>

<res-ref-name>jdbc/mysql</res-ref-name>

<res-type>javax.sql.DataSource</res-type>

<res-auth>Container</res-auth>

</resource-ref>

</web-app>

这用来指明数据库连接池。然后是设置Hibernate使用这个容器管理的连接池来连接数据库：在classes目录下建一个hibernate.cfg.xml，写入

<?xml version='1.0' encoding='utf-8'?>

<!DOCTYPE hibernate-configuration

PUBLIC "-//Hibernate/Hibernate Configuration DTD//EN"

"http://hibernate.sourceforge.net/hibernate-configuration-2.0.dtd">

<hibernate-configuration>

<session-factory>

<property name="connection.datasource">java:comp/env/jdbc/mysql</property>

<property name="show_sql">false</property>

<property name="dialect">net.sf.hibernate.dialect.MySQLDialect</property>

<!-- Mapping files -->

<mapping resource="Cat.hbm.xml"/>

</session-factory>

</hibernate-configuration>

这里可以看到连接的设置，其中dialect是用来指明一个类，来处理数据库数据类型和Java数据类型之间的对照的。<mapping resource="Cat.hbm.xml"/>是映射设置，下面会提到。先看看根据数据库表结构制作的java bean：

数据库结构为：CAT

Column | Type | Modifiers

--------+-----------------------+-----------

cat_id | character(32) | not null

name | character varying(16) | not null

sex | character(1) |

weight | real |

Indexes: cat_pkey primary key btree (cat_id)

对应的java bean源程序：

package net.sf.hibernate.examples.quickstart;

public class Cat {

private String id;

private String name;

private char sex;

private float weight;

public Cat() {

}

public String getId() {

return id;

}

private void setId(String id) {

this.id = id;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public char getSex() {

return sex;

}

public void setSex(char sex) {

this.sex = sex;

}

public float getWeight() {

return weight;

}

public void setWeight(float weight) {

this.weight = weight;

}

}

然后在classes目录下创建一个Cat.cfg.xml来配置PO对象：

<?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="net.sf.hibernate.examples.quickstart.Cat" table="CAT">

<!-- A 32 hex character is our surrogate key. It's automatically

generated by Hibernate with the UUID pattern. -->

<id name="id" type="string" unsaved-value="null" >

<column name="CAT_ID" sql-type="char(32)" not-null="true"/>

<generator class="uuid.hex"/>

</id>

<!-- A cat has to have a name, but it shouldn' be too long. -->

<property name="name">

<column name="NAME" length="16" not-null="true"/>

</property>

<property name="sex"/>

<property name="weight"/>

</class>

</hibernate-mapping>

在这里可以看到java bean类net.sf.hibernate.examples.quickstart.Cat和数据库表CAT的映射关系。

编译好Cat类，放到相应目录下，OK，配置就完成了。下面是在JSP里应用的例子。

首先我们再创建一个类HibernateUtil，用来处理一些诸如取/关Session的功能，这些功能也可以直接写在JSP里：

package net.sf.hibernate.examples.quickstart;

import org.apache.commons.logging.Log;import org.apache.commons.logging.LogFactory;

import net.sf.hibernate.*;

import net.sf.hibernate.cfg.*;

public class HibernateUtil {

private static Log log = LogFactory.getLog(HibernateUtil.class);

private static final SessionFactory sessionFactory;

static {

try {

// Create the SessionFactory

sessionFactory = new Configuration().configure().buildSessionFactory();

} catch (Throwable ex) {

log.error("Initial SessionFactory creation failed.", ex);

throw new ExceptionInInitializerError(ex);

}

}

public static final ThreadLocal session = new ThreadLocal();

public static Session currentSession() throws HibernateException {

Session s = (Session) session.get();

// Open a new Session, if this Thread has none yet

if (s == null) {

s = sessionFactory.openSession();

session.set(s);

}

return s;

}

public static void closeSession() throws HibernateException {

Session s = (Session) session.get();

session.set(null);

if (s != null)

s.close();

}

}

然后是Cat.JSP，很简单

<%@ page language="java" pageEncoding="GB2312" %>

<%@ page import="net.sf.hibernate.Transaction"%>

<%@ page import="net.sf.hibernate.Session"%>

<%@ page import="net.sf.hibernate.cfg.*"%>

<%@ page import="net.sf.hibernate.Query"%>

<%@ page import="net.sf.hibernate.examples.quickstart.HibernateUtil"%>

<%@ page import="net.sf.hibernate.examples.quickstart.Cat"%>

<%@ page import="java.util.*"%><!DOCTYPE HTML PUBLIC "-//w3c//dtd html 4.0 transitional//en"><html><head><title>Lomboz JSP</title></head><body bgcolor="#FFFFFF">

<%

//添加一只Cat

Session ses = HibernateUtil.currentSession();

Transaction tx= ses.beginTransaction();

Cat princess = new Cat();

princess.setName("ahxu");

princess.setSex('F');

princess.setWeight(7.4f);

ses.save(princess);

tx.commit();

HibernateUtil.closeSession();

//读取库里所有Cat

ses = HibernateUtil.currentSession();

tx= ses.beginTransaction();

Query query = ses.createQuery("select c from Cat as c where c.sex = :sex");

query.setCharacter("sex", 'F');

for (Iterator it = query.iterate(); it.hasNext();) {

Cat cat = (Cat) it.next();

out.println("Female Cat: " + cat.getName() );

}

tx.commit();

HibernateUtil.closeSession();

%>

</body>

</html>