Hibernate开发步骤

     首先，可以写一个Hibernate自动在数据库中建表的工具类,当然也可以在配置文件hibernate.cfg.xml中配置,<property  name="hibernate.hbm2ddl.auto">create</property>
不过在创建表后，一定要配置文件改回来，否则在你再执行程序时，它会把以前已经创建的表删除，重新建表。这样就会造成以前保存的数据丢失。

建表类：

package util;

import org.hibernate.cfg.Configuration;
import org.hibernate.tool.hbm2ddl.SchemaExport;

public class CreateTable {
    
   /**
     * 根据映射文件建表
      * @para args
     */
    public static void main(String[] args) {
       Configuration cfg = new Configuration().configre;//读的是xml文件
       SchemaExport se = new SchemaExport(cfg);
       se.create(true,true); 
    }
}

    再写一个Hibernate获取Session的工具类，因为SessionFactory是重量级的，最好只创建一次。

package util;

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

public class HbnUtil {
    private static SessionFactory factory = null;
    
    static {
       //读取配置文件,加载默认配置文件hibernate.cfg.xml
       Configuration cfg = new Configuration().configure();
       //初始化配置文件中信息，实例化SessionFactory
       factory = cfg.buildSessionFactory();       
    }
    public static Session getSession(){
        return sf.openSession();//创建Session
    }
	
    public static void closeSession(Session s){
        if (s != null && s.isOpen()){
	   s.close();
        }
    }
}

一个纯Java类（POJO）此类中只含有属性、构造方法、get/set方法

package entity;

import java.util.Date;

public class Classes {
	private int oid;//代理主键,用于建表
	private String className;//班级名
	private int total;//总人数
	private Date openDate;//开班日期
	
	public int getOid() {
		return oid;
	}
	public void setOid(int oid) {
		this.oid = oid;
	}
	public String getClassName() {
		return className;
	}
	public void setClassName(String className) {
		this.className = className;
	}
	public int getTotal() {
		return total;
	}
	public void setTotal(int total) {
		this.total = total;
	}
	public Date getOpenDate() {
		return openDate;
	}
	public void setOpenDate(Date openDate) {
		this.openDate = openDate;
	}
	
}

配置的实体类与表的映射文件Classes.hbm.xml，类名-->表名  类的属性-->表的字段（column）
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping
PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="entity.Classes" table="t_classes">
<id name="oid" column="id">
<generator class="native"></generator>
</id>
<property name="className" column="class_name"
   length="50" type="string"/>
<property name="total" type="integer"/>
<property name="openDate" column="open_date"
type="date"></property>
</class>
</hibernate-mapping>

Hibernate的配置文件hibernate.cfg.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<property name="show_sql">true</property>
<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="hibernate.connection.url">jdbc:mysql://127.0.0.1:3306/hibernatedb</property>
<property name="hibernate.connection.username">root</property>
<property name="hibernate.connection.password"></property>
<property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
<property name="hibernate.format_sql">true</property>
<!--
<property name="hibernate.hbm2ddl.auto">create</property>


<property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
<property name="connection.url">jdbc:oracle:thin:@192.168.0.23:1521:tarena</property>
<property name="connection.username">openlab</property>
<property name="connection.password">open123</property>
<property name="dialect">org.hibernate.dialect.Oracle9Dialect</property>

-->
<mapping resource="entity/User.hbm.xml"/>
<mapping resource="entity/Classes.hbm.xml"/>

</session-factory>
</hibernate-configuration>

最后是一个简单测试类

package test;

import java.text.SimpleDateFormat;
import java.util.List;

import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.Transaction;

import util.HbnUtil;
import entity.Classes;

public class TestClasses {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		//创建持久对象的操作对象Session
		Session session = HbnUtil.getSession();
		try {
			//开启事务
			Transaction tx = session.beginTransaction();
			Classes c = new Classes();
			c.setClassName("SD0901");
			c.setTotal(43);
			SimpleDateFormat sdf = new SimpleDateFormat("yyyy/MM/dd");
			c.setOpenDate(sdf.parse("2009/01/01"));
			//保存对象
			session.save(c);
			//修改班级名称
			c.setClassName("ASD0901");
			//删除对象
			session.delete(c);
			//根据对象id来查找对象
			//get()/load()
			Classes cl = (Classes)session.get(Classes.class, 1);
			System.out.println("Id为1的班级名称："+cl.getClassName());
			
			//定义查询对象,HQL
			Query query = session.createQuery("from Classes");
			//执行查询
			List<Classes> all = query.list();
			for(Classes classes:all){
				System.out.println("班级名称:"+classes.getClassName());
			}
			//提交事务
			tx.commit();
			
		} catch (Exception e) {
			session.getTransaction().rollback();
			e.printStackTrace();
		} finally{
			HbnUtil.closeSession(session);
		}
		
	}

}

以上是一个很简单的例子。O(∩_∩)O