Hibernate——以面向对象的思维操作关系数据库（一）

Hibernate是一个轻量级的ORM开源框架。Hibernate解脱了面对繁琐的JDBC的开发者，使得变成更加面向对象化，将之前的连接语句，增删改查等语句进行了很好的封装，使得业务逻辑等的编写更加的容易；使移植数据库也变得十分的容易，即根据不同的数据库配置configuration.cfg.xml就可以轻松改变数据库；下面以一个代码段稍作解释：

一 ：每个相对应的实体都会有相对应的映射文件，映射文件的作用主要是维护实体间的关系。

实体类User：

package com.bjpowernode.hibernate;import java.util.Date;public class User {private String id;private String name;private String password;private Date createTime;private Date expireTime;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 createTime) {this.createTime = createTime;}public Date getExpireTime() {return expireTime;}public void setExpireTime(Date expireTime) {this.expireTime = expireTime;}}

映射文件：

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

将映射文件生成dll文件：

package com.bjpowernode.hibernate;import org.hibernate.cfg.Configuration;import org.hibernate.tool.hbm2ddl.SchemaExport;/** * 将hbm生成ddl * @author Administrator * */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);}}

二 ：在configuration.cfg.xml中配置基本信息，并将映射文件信息配置到configuration.cfg.xml中

configuration.cfg.xml配置文件：

<!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.driver_class">com.mysql.jdbc.Driver</property><property name="hibernate.connection.url">jdbc:mysql://localhost:3306/hibernate_first</property><property name="hibernate.connection.username">root</property><property name="hibernate.connection.password">bjpowernode</property><property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property><property name="hibernate.show_sql">true</property><mapping resource="com/bjpowernode/hibernate/User.hbm.xml"/></session-factory></hibernate-configuration>

三：建立客户端类Client，添加用户数据到数据库

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SessionFactorySessionFactory factory = cfg.buildSessionFactory();//取得sessionSession 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User对象session.save(user);//提交事务session.getTransaction().commit();}catch(Exception e) {e.printStackTrace();//回滚事务session.getTransaction().rollback();}finally {if (session != null) {if (session.isOpen()) {//关闭sessionsession.close();}}}}}

总结：上面只是一个小例子，但是从小例子中我们依稀可以感受到那种封装给我们带来的便捷了。