新手上路之Hibernate:第一个Hibernate例子
一、Hibernate概述
(一)什么是Hibernate?
Hibernate核心内容是ORM(关系对象模型)。可以将对象自动的生成数据库中的信息,使得开发更加的面向对象。这样作为程序员就可以使用面向对象的思想来操作数据库,而不用关心繁琐的JDBC。所以,Hibernate处于三层架构中的D层(持久层)。
(二)使用Hibernate的优点
1、Hibernate可以使用在java的任何项目中,不一定非要使用在java web项目中。因为Hibernate不需要类似于tomact这些容器的支持,可以直接通过一个main方法进行测试。
2、通过下面的实例,可以发现使用Hibernate可以大大减少代码量。
3、由于使用了Hibernate,代码中不涉及具体的JDBC语句,所以就方便了代码的可移植性。
二、Hibernate开发的环境搭建
- <!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>
- <!– mysql数据库名称 –>
- <property name=“hibernate.connection.url”>jdbc:mysql://localhost:3306/hibernate_first</property>
- <!– 数据库的登陆用户名 –>
- <property name=“hibernate.connection.username”>root</property>
- <!– 数据库的登陆密码 –>
- <property name=“hibernate.connection.password”>root</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>
- </session-factory>
- </hibernate-configuration>
<!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> <!-- mysql数据库名称 --> <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/hibernate_first</property> <!-- 数据库的登陆用户名 --> <property name="hibernate.connection.username">root</property> <!-- 数据库的登陆密码 --> <property name="hibernate.connection.password">root</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> </session-factory> </hibernate-configuration>
三、HIbernate第一个实例
- import java.util.Date;
- public class User {
- private String id;
- private String username;
- private String password;
- private Date createTime;
- private Date expireTime;
- public String getId() {
- return id;
- }
- public void setId(String id) {
- this.id = id;
- }
- public String getUsername() {
- return username;
- }
- public void setUsername(String userName) {
- this.username = userName;
- }
- 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;
- }
- }
import java.util.Date; public class User { private String id; private String username; private String password; private Date createTime; private Date expireTime; public String getId() { return id; } public void setId(String id) { this.id = id; } public String getUsername() { return username; } public void setUsername(String userName) { this.username = userName; } 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; } }
- <?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.example.hibernate.User”>
- <id name=“id”>
- <generator class=“uuid”/>
- </id>
- <property name=“username”/>
- <property name=“password”/>
- <property name=“createTime”/>
- <property name=“expireTime”/>
- </class>
- </hibernate-mapping>
<?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.example.hibernate.User"> <id name="id"> <generator class="uuid"/> </id> <property name="username"/> <property name="password"/> <property name="createTime"/> <property name="expireTime"/> </class> </hibernate-mapping>
其中的property标签是将要生成是数据库表中的字段,在这里不用关心各个字段是什么类型的。因为Hibernate会根据上面的实体类中属性的类型来决定将来表中字段的类型
- <hibernate-configuration>
- <session-factory >
- <!– mysql数据库驱动 –>
- <property name=“hibernate.connection.driver_class”>com.mysql.jdbc.Driver</property>
- <!– mysql数据库名称 –>
- <property name=“hibernate.connection.url”>jdbc:mysql://localhost:3306/hibernate_first</property>
- <!– 数据库的登陆用户名 –>
- <property name=“hibernate.connection.username”>root</property>
- <!– 数据库的登陆密码 –>
- <property name=“hibernate.connection.password”>root</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>
- <SPAN style=“COLOR: #ff0000”><mapping resource=“com/example/hibernate/User.hbm.xml”/></SPAN>
- </session-factory>
- </hibernate-configuration>
<hibernate-configuration> <session-factory > <!-- mysql数据库驱动 --> <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property> <!-- mysql数据库名称 --> <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/hibernate_first</property> <!-- 数据库的登陆用户名 --> <property name="hibernate.connection.username">root</property> <!-- 数据库的登陆密码 --> <property name="hibernate.connection.password">root</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> <mapping resource="com/example/hibernate/User.hbm.xml"/> </session-factory> </hibernate-configuration>
注意:必须是“/”而不能是“.”。
- import org.hibernate.cfg.Configuration;
- import org.hibernate.tool.hbm2ddl.SchemaExport;
- /**
- * 将hbm生成ddl
- * @author BCH
- *
- */
- public class ExoprtDB {
- public static void main(String[] args) {
- //默认读取hibernate.cfg.xml文件
- Configuration cfr = new Configuration().configure();
- SchemaExport export = new SchemaExport(cfr);
- export.create(true, true);
- }
- }
import org.hibernate.cfg.Configuration; import org.hibernate.tool.hbm2ddl.SchemaExport; /** * 将hbm生成ddl * @author BCH * */ public class ExoprtDB { public static void main(String[] args) { //默认读取hibernate.cfg.xml文件 Configuration cfr = new Configuration().configure(); SchemaExport export = new SchemaExport(cfr); export.create(true, true); } }
到这里就可以生成User表了,但是如果直接运行ExoprtDB.java文件是不能生成User表的。因为在mysql数据中还没有建立数据库Hibernate-first。所以在mysql控制台中通过create database hibernate-first; use hibernate-first;之后再执行ExoprtDB.java文件就可以生成表了。
- 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) {
- //读取配置文件
- Configuration cfg = new Configuration().configure();
- SessionFactory factory = cfg.buildSessionFactory();
- Session session = null;
- try{
- session = factory.openSession();
- //开启事务
- session.beginTransaction();
- User user = new User();
- user.setUsername(“用户名”);
- user.setPassword(“123”);
- user.setCreateTime(new Date());
- user.setExpireTime(new Date());
- 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session
- session.close();
- }
- }
- }
- }
- }
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) { //读取配置文件 Configuration cfg = new Configuration().configure(); SessionFactory factory = cfg.buildSessionFactory(); Session session = null; try{ session = factory.openSession(); //开启事务 session.beginTransaction(); User user = new User(); user.setUsername("用户名"); user.setPassword("123"); user.setCreateTime(new Date()); user.setExpireTime(new Date()); 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session session.close(); } } } } }