首先，什么是映射

       Hibernate的映射分类，小编简单的画了一张思维导图，如下所示：

        接着，小编结合deom来具体的讲解一下基本映射。

        小试牛刀

        第一步、我们使用XML配置映射代码如下：

<?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 package="com.bjpowernode.hibernate">
	<class name="User3" table="t_user3">
		<id name="id" >
			<generator class="assigned"/>		
		</id>
		<property name="name" length="30" unique="true" not-null="true"/>
		<property name="password"/>		
		<property name="expireTime" column="expireTime" not-null="false" type="date"/>
		<property name="createTime" column="createTime" not-null="false" type="date"/>			
	</class>
	
</hibernate-mapping>

package com.bjpowernode.hibernate;

import java.util.Date;

public class User3 {

	private int id;
	
	private String name;
	
	private String password;
	
	private Date createTime;
	
	private Date expireTime;

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getPassword() {
		return password;
	}

	public void setPassword(String password) {
		this.password = password;
	}

	public Date getCreateTime() {
		return createTime;
	}

	public void setCreateTime(Date createTime) {
		this.createTime = createTime;
	}

	public Date getExpireTime() {
		return expireTime;
	}

	public void setExpireTime(Date expireTime) {
		this.expireTime = expireTime;
	}

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}
}

<!DOCTYPE hibernate-configuration PUBLIC
	"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
	<session-factory >
		<!-- MySql数据库驱动 -->
		<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
		<!-- 数据库名称 -->
		<property name="hibernate.connection.url"> jdbc:mysql:///hibernate_basemapping</property>
		<!-- 数据库的用户名 -->
		<property name="hibernate.connection.username">root</property>
		<!-- 数据库的密码 -->
		<property name="hibernate.connection.password">123456</property>
		<!-- 方言：为每一种数据库提供适配器，方便转换 -->  
		<property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
		<!-- 显示语句 -->
		<property name="hibernate.show_sql">true</property>
		<!-- 格式排版 -->
		<!-- <property name="hibernate.format_sql">true</property> -->	
		<mapping resource="com/bjpowernode/hibernate/User3.hbm.xml"/>
				
	</session-factory>
</hibernate-configuration>

package com.bjpowernode.hibernate;
import org.hibernate.cfg.Configuration;
import org.hibernate.tool.hbm2ddl.SchemaExport;

/**
 * 将hbm生成ddl
 * @author 丁国华
 *
 */
public class ExportDB {

	public static void main(String[] args) {
		
		//默认读取hibernate.cfg.xml文件
		Configuration cfg = new Configuration().configure();		
		SchemaExport export = new SchemaExport(cfg);
		export.create(true, true);
	}
}

         第五步、编写客户端Client.java，添加用户数据到数据库，代码如下所示：

package com.bjpowernode.hibernate;

import java.util.Date;

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

public class Client {
	
	public static void main(String[] args){
		
		//读取hibernate.cfg.xml文件
		Configuration cfg = new Configuration().configure();		
		//建立SessionFactory
		SessionFactory factory = cfg.buildSessionFactory();		
		//取得session
		Session session = null;
		try{
			session = factory.openSession();
			//开启事物
			session.beginTransaction();
			User3 user = new User3();
			user.setId(1000);
			user.setName("张三");
			user.setPassword("123");
			user.setCreateTime(new Date());
			user.setExpireTime(new Date());
			
			//保存user对象
			session.save(user);			
			//提交事物
			session.getTransaction().commit();						
		}catch (Exception e){
			e.printStackTrace();
			//回滚事物
			session.getTransaction().rollback();
			
		}finally{
			if (session != null){
				if(session.isOpen()){
					//关闭session
					session.close();
				}
			}
			
		}
						
	}

}

       最后，来运行一下，看看我们的数据库，效果如下所示：

       
       小编寄语：该博文，小编主要介绍了hibernate中的基本映射，分别从什么是映射、ORM的实现原理、映射的分类、配上demo进行讲解，希望可以帮助有需要的小伙伴们，有不同意见的小伙伴欢迎在下方留言，在后续SSH系列博文中，小编将继续介绍hibernate的相关知识，敬请期待`(*∩_∩*)′。