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Hibernate初体验Cat之快速上手

ahxu

Hibernate的手册里的Cat例子感觉很不明了，很难照着它轻松的运行起第一个例子，费了点周折，总算看到一点结果，如果你是新手，可以参考一下，少走一些弯路。

1.下载tomcat和Hibernate 2. 安装

以tomcat+mysql+hibernate为例

tomcat的安装，及mysql的安装和DBCP的配制参见http://blog.csdn.net/ahxu/archive/2004/09/01/91611.aspx，这里就不提了，这里假设tomcat+mysql已经配置并测试可用，这里%WebApp%代表你已配置好的一个web应用的root，着重说一下hibernate的安装，

1) 解压下载的压缩包，将解压出来的hibernate2.jar复制到%WebApp%/WEB-INF/lib

2) 将解压出来的lib目录下的

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

文件同样复制到%WebApp%/WEB-INF/lib，具体请参见解压出来的lib目录下的readme.txt。

3) 将解压出来的etc目录下的

log4j.properties

文件复制到%WebApp%/WEB-INF/classes。

3.编写相关文件

1) 按照参考文档，配置hibernate，将以下代码保存为hibernate.cfg.xml放在%WebApp%/WEB-INF/classes下

<?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>

NOTE：这里与hibernate文档里的不一样，这里指定数据源为mysql数据库jdbc/mysql，方言dialect为net.sf.hibernate.dialect.MySQLDialect。

2) 将以下代码保存为Cat.java，并生成相应的Cat.class，放入%WebApp%/WEB-INF/classes，这里无论你用什么方法生成Cat.class，但最终Cat.class应在%WebApp%/WEB-INF/classes/net/sf/hibernate/examples/quickstart目录下

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;
}

}

3) 将以下代码保存为O/R映射文件Cat.hbm.xml，放入%WebApp%/WEB-INF/classes 

<?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

4) 在数据库内建表，结构如下 

 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)

5) 将以下代码保存为HibernateUtil.java，并生成相应的HibernateUtil.class，放入%WebApp%/WEB-INF/classes，同样注意package

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();
}
}

NOTE:这里与hibernate文档也不同，原文档编绎时缺少2个包，这里已加上。

6) 将以下代码保存为test.jsp，放入%WebApp%/，用http测试 

<%@ 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>

小结

步骤基本与原文档步骤相同，只是做了一些补充，方便上手，这里并没有对其中的一些配置做具体解释，如有疑问请参见发行包中的相关文档。

以上tomcat5.027 + hibernate2.1.6测试通过

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