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>