Hibernate第01课：第一个Hibernate

Hibernate持久层框架的使用

首先建立一个JavaProject,Hibernate的测试非常简单,没有环境要求,只需要几个Hibernate的jar包就可以测试,所以Hibernate没有侵入性,称为轻量级框架.

现在将步骤列举如下,供复习使用,:

一、配置Hibernate环境

1.拷贝Hibernate需要的jar包：

*Hibernate_HOME/Hibernate.jar

*Hibernate_HOME/lib/*.jar

*MySQLjdbc驱动(这里使用MySQL作为数据库)

2.创建hibernate.cfg.xml文件,可以在Hibernate_HOME下的实例拷贝一个模板

*Hibernate是一个ORM映射框架,这个文件就是映射的桥梁.

    3.配置hibernate.cfg.xml,设置数据库连接,具体的的内容意思不做详细解释 

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

<hibernate-configuration>
	<session-factory>
		<property name="hibernate.connection.url">jdbc:mysql://localhost/hibernate</property>
		<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
		<property name="hibernate.connection.username">root</property>
		<property name="hibernate.connection.password">root</property>
		<!-- 声明MySQL方言 -->
		<property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
		<!-- 是否在控制台显示SQL语句 -->
		<property name="hibernate.show_sql">true</property>

		<!-- 加载映射对象 -->
		<mapping resource="net/knight/hibernate/User.hbm.xml"/>
	</session-factory>
</hibernate-configuration>

     4.创建log4j.properties,便于调试

     5.创建对象net.knight.hibernate.User.java

package net.knight.hibernate;

import java.util.Date;

public class User {

	private String id;
	
	private String name;
	
	private String password;
	
	private Date createTime;// 创建日期
	
	private Date expireTime; // 失效日期

	public String getId() {
		return id;
	}

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

	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 creatTime) {
		this.createTime = creatTime;
	}

	public Date getExpireTime() {
		return expireTime;
	}

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

     6.创建对象映射文件User.hbm.xml

<?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="net.knight.hibernate.User">
		<id name="id">
			<generator class="uuid"/>
		</id>
		<property name="name"/>
		<property name="password"/>
		<property name="createTime"/>
		<property name="expireTime"/>
	</class>
</hibernate-mapping>

     7.因为要将对象导入到表,所以要先建立数据库,我的数据库名称叫Hibernate,可以根据自己的要求改,改完后hibernate.cfg.xml中的jdbc连接需要和你的数据库一致.

     8.为了生成表,建立一个生成表工具类net.knight.hibernate.ExportDB.java

package net.knight.hibernate;

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

public class ExportDB {

	/**
	 * 生成表工具类
	 */
	public static void main(String[] args) {
		// 读取配置文件hibernate.cfg.xml
		// Configuration cfg = new Configuration();读取.properties文件
		Configuration cfg = new Configuration().configure();
		
		// 将对象导成表
		SchemaExport export = new SchemaExport(cfg);		
		export.create(true, true);
	}
}

     9.执行这个类,打开MySQL客户端,登录

        * 输入use hibernate;切换数据库

        * 输入desc User;可以看到表已经建立好了.

    10.写一个客户端类,在表中增加一条记录net.knight.hibernate.Client

package net.knight.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配置文件
		Configuration cfg = new Configuration().configure();
		
		// 创建SessionFactory
		SessionFactory factory = cfg.buildSessionFactory();
		
		Session session = null;
		
		try {
			session = factory.openSession();
			
			// 开启事务
			session.beginTransaction();
			User user = new User();
			user.setName("张三");
			user.setPassword("123");
			user.setCreateTime(new Date());
			user.setExpireTime(new Date());
			
			// 保存数据
			session.save(user);

			// 提交事务
			session.getTransaction().commit();
		}catch(Exception e) {
			e.printStackTrace();
			// 回滚事务
			session.getTransaction().commit();
		}finally {
			if(session != null) {
				if(session.isOpen()) {
					// 关闭事务
					session.close();
				}
			}
		}
	}
}

     11.在MySQL客户端输入select * from user;应该可以看到添加的结果.

重点:先建立对象,再建立对象和数据库的映射文件.以及Hibernate中常用的几个方法.

文件目录结构如下

Hibernate

    |_____lib

    |           |_____*.jar

    |_____net

    |            |_____knight

    |                           |_______hibernate

    |                                                |________User.java

    |                                                |________User.hbm.xml

    |                                                |________ExportDB.java

    |                                                |________Client.java

    |_____hibernate.cfg.xml

    |_____log4j.properties