Hibernate 最简单实例

我从网上下载了 hibernate-release-4.3.0.Final.zip,解压缩,把/lib/required文件夹下的所有jar包加入到eclipse项目中的Referenced Libraries里面。然后,我粗略地阅读了documentation/manual/en-US/html/下的文档,按部就班地做了如下的最简单实例(添加了一些修改)。由于文档中用的是HSQLDB,我就从网上下载了hsqldb-2.3.1.zip,解压缩,把/lib下的两个Jar包同样加入项目。在HSQLDB的/bin目录下,运行runServer.bat以启动数据库,再运行runManagerSwing.bat以启动管理数据库的简单GUI工具(选择HSQL Database Engine Server)。项目所要用到的一个表格的创建SQL为:

CREATE TABLE EVENTS
(
EVENT_ID INT IDENTITY,
EVENT_DATE DATE,
EVENT_TITLE VARCHAR(100)
)

Eclipse项目的根目录就是自带的src目录,在其下新建一个hibernate.cfg.xml。其内容为:

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

    <session-factory>

        <!-- Database connection settings -->
        <property name="connection.driver_class">org.hsqldb.jdbcDriver</property>
        <property name="connection.url">jdbc:hsqldb:hsql://localhost</property>
        <property name="connection.username">sa</property>
        <property name="connection.password"></property>

        <!-- JDBC connection pool (use the built-in) -->
        <property name="connection.pool_size">1</property>

        <!-- SQL dialect -->
        <property name="dialect">org.hibernate.dialect.HSQLDialect</property>

        <!-- Enable Hibernate's automatic session context management -->
        <property name="current_session_context_class">thread</property>

        <!-- Disable the second-level cache  -->
        <property name="cache.provider_class">org.hibernate.cache.internal.NoCacheProvider</property>

        <!-- Echo all executed SQL to stdout -->
        <property name="show_sql">true</property>

        <!-- Drop and re-create the database schema on startup -->
        <property name="hbm2ddl.auto">update</property>

        <mapping resource="com/example/domain/Event.hbm.xml"/>

    </session-factory>

</hibernate-configuration>

以上代码实测可行,不用修改。

模型类都放在了com.example.domain目录下。这个例子中只有一个类,为Event:

package com.example.domain;

import java.util.Date;

public class Event {
    
    private Long id;
    private String title;
    private Date date;

    public Event() {
    }
    public Long getId() {
        return id;
    }
    private void setId(Long id) {
        this.id = id;
    }
    public Date getDate() {
        return date;
    }
    public void setDate(Date date) {
        this.date = date;
    }
    public String getTitle() {
        return title;
    }
    public void setTitle(String title) {
        this.title = title;
    }
}

用行话说,就是一个普通JavaBean,一个POJO。

还要放在com.example.domain目录中的、与Event.java靠在一起的是它的ORM配置文件,Event.hbm.xml:

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="com.example.domain">
    <class name="Event" table="EVENTS">
        <id name="id" column="EVENT_ID">
            <generator class="native" />
        </id>
        <property name="date" type="timestamp" column="EVENT_DATE"/>
        <property name="title" type="string" column="EVENT_TITLE"/>
    </class>
</hibernate-mapping>

映射比较明了,有关generator的详细信息这里不提及。

根据官方文档里面给出的示例,我也建立了一个Hibernate助手类:HibernateUtil,放在com.example.util包下:

package com.example.util;

import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class HibernateUtil {

    private static final SessionFactory sessionFactory = buildSessionFactory();

    private static SessionFactory buildSessionFactory() {
        try {
            // Create the SessionFactory from hibernate.cfg.xml
            return new Configuration().configure().buildSessionFactory();
        }
        catch (Throwable ex) {
            // Make sure you log the exception, as it might be swallowed
            System.err.println("Initial SessionFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }

    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }
    
}

这个类我也是照抄的,用于提供SessionFactory对象。不过其中的buildSessionFactory显示为Depricated,有待进一步解决。

最后一个类,即有main函数的EventManager.java,放在com.example包下:

package com.example;

import java.util.Date;
import org.hibernate.Session;
import com.example.domain.Event;
import com.example.util.HibernateUtil;

public class EventManager {

    private void createAndStoreEvent(String title, Date theDate) {
        Session session = HibernateUtil.getSessionFactory().getCurrentSession();
        session.beginTransaction();

        Event theEvent = new Event();
        theEvent.setTitle(title);
        theEvent.setDate(theDate);
        session.save(theEvent);

        session.getTransaction().commit();
    }
    
    public static void main(String[] args) {
        EventManager mgr = new EventManager();
        mgr.createAndStoreEvent("My Event", new Date());
        HibernateUtil.getSessionFactory().close();
    }

}

运行EventManager,在HSQLDB的Swing GUI工具里面运行Select * from EVENTS,就可以看到刚刚插入的一行数据了。

结果为:

1月5日也是我的生日哦!对的,今天我过生日。(^_^)

posted @ 2014-01-05 16:13  XIAOSHUA  阅读(368)  评论(0编辑  收藏  举报