hibernate使用 自动建表

hibernate.cfg.xml配置文件内容如下，注意一点的是，当你想运行时就自动建表，而不用再到数据库用SQL来创建数据库的话，就要在<session-factory>标签内加入如下配置信息:

<property name="hbm2ddl.auto">create</property>

 

当hibernate与spring集成在一起，没有单独的hibernate.cfg.xml文件时，就要在spring配置文件里的sessionFactory标签里，配置如下信息：

<property name="hibernateProperties">
   <props>
    <prop key="hibernate.dialect">org.hibernate.dialect.MySQLDialect</prop>
        <prop key="hbm2ddl.auto">update</prop>

</props> 

</property> 

 

 

转:

首先介绍其中的一个属性hbm2ddl.auto，这个就是这个方案的核心属性，有四个值：create，create-drop，update，validate。它的含义如下：

<!-- 启动时删数据库中的表，然后创建，退出时不删除数据表
<property name="hbm2ddl.auto">create</property>-->
<!-- 启动时删数据库中的表，然后创建，退出时自动删除所有表
<property name="hbm2ddl.auto">create-drop</property>-->
<!-- 自动修改，如果表结构与实体类不一致，那么就修改表使它们一致，数据会保留
<property name="hbm2ddl.auto">update</property>-->
<!-- 自动校验，如果表结构与实体类不一致，那么不做任何操作，报错
<property name="hbm2ddl.auto">validate</property>-->

 

 

hibernate.cfg.xml代码

<?xml version='1.0' encoding='UTF-8'?><!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"><!-- Generated by MyEclipse Hibernate Tools. --><hibernate-configuration><session-factory><!-- 各属性的配置--><!-- 启动时删数据库中的表，然后创建，退出时不删除数据表，如果没有下面的属性的话，那么要手动写sql语句来建表，才能进行数据库的操作--><property name="hbm2ddl.auto">create</property><!--为true表示将Hibernate发送给数据库的sql显示出来 --><property name="show_sql">true</property><!-- SQL方言，这边设定的是MySQL --><property name="dialect">org.hibernate.dialect.MySQL5Dialect</property><!-- 一次读的数据库记录数 --><property name="jdbc.fetch_size">50</property><!-- 设定对数据库进行批量删除 --><property name="jdbc.batch_size">30</property><!--驱动程序--><property name="connection.driver_class">com.mysql.jdbc.Driver</property><!-- JDBC URL --><property name="connection.url">jdbc:mysql://localhost/testWTB?characterEncoding=gb2312</property><!-- 数据库用户名--><property name="connection.username">root</property><!-- 数据库密码--><property name="connection.password"></property><!--映射文件 --><!-- <mapping resource="com/amigo/pojo/User.hbm.xml" /><mapping resource="com/amigo/pojo/Org.hbm.xml" />--><mapping class="com.ajax.employee.model.Employee"/> </session-factory></hibernate-configuration>

 

实体类Employee.java

package com.ajax.employee.model;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.GeneratedValue;import javax.persistence.GenerationType;import javax.persistence.Id;import javax.persistence.Table;import javax.persistence.TableGenerator;@Entity@Table(name = "EMPLOYEE")public class Employee implements java.io.Serializable{private Integer employee_id; //人员ID（主键）private String employee_name; //人员姓名private String sex; //性别private String birthday; //出生日期private String address; //地址@Id@Column(name = "EMPLOYEE_ID")@TableGenerator( name="tab-store",//产生器的名字，也就是下面的generator的名字 table="GENERATOR_TABLE",//产生器的table名 pkColumnName = "G_KEY",//与employee这张表关联的外键列名 pkColumnValue="EMPLOYEE_PK",//向这generator表的这个与employee表关联的列的值赋为EMPLOYEE_PK valueColumnName = "G_VALUE",//外键参考的值 allocationSize=1//产生器表的初始值，这个值是指id的初始值，当插入第一条记录后，那么这条记录分配到的id值为1,而在generator_table表里的G_VALUE一栏的值变为2，即它是下一次插入记录的id准备值)@GeneratedValue(strategy = GenerationType.TABLE,generator="tab-store")//用表产生器来产生id值，这样会在数据新建表产生器表，产生器表记录只有一条，很简单，只用来记录下一个分配出去id值为多少//@GeneratedValue(strategy = GenerationType.AUTO)public Integer getEmployee_id() {return employee_id;}public void setEmployee_id(Integer employee_id) {this.employee_id = employee_id;}public String getEmployee_name() {return employee_name;}public void setEmployee_name(String employee_name) {this.employee_name = employee_name;}public String getSex() {return sex;}public void setSex(String sex) {this.sex = sex;}public String getBirthday() {return birthday;}public void setBirthday(String birthday) {this.birthday = birthday;}public String getAddress() {return address;}public void setAddress(String address) {this.address = address;}}

 

DAO类：

package com.ajax.core;import java.io.Serializable;import org.apache.commons.logging.Log;import org.apache.commons.logging.LogFactory;import org.hibernate.Session;import org.hibernate.Transaction;/** * 抽象Dao类，用于持久化操作 * @author 菠萝大象 * @version 1.0 */public abstract class BaseDao<T> {private static Log log = LogFactory.getLog(BaseDao.class);/** * 获取Hibernate的Session对象 */public Session getSession(){ return HibernateSessionFactory.getSession(); }/** * 根据主键得到对象 */public T getObject(Class clazz, Serializable id){return (T)getSession().get(clazz, id);}/** * 保存对象 */public void saveObject(T t) {Session session = getSession();Transaction tx = beginTransaction(session);try{session.saveOrUpdate(t);tx.commit();}catch(Exception e){tx.rollback();log.error("保存对象失败");}}/** * 更新对象 */public void updateObject(T t){Session session = getSession();Transaction tx = beginTransaction(session);try{session.update(t);tx.commit();}catch(Exception e){tx.rollback();log.error("更新对象失败");}}/** * 删除对象 */public void removeObject(T t) {Session session = getSession();Transaction tx = beginTransaction(session);try{session.delete(t);tx.commit();}catch(Exception e){tx.rollback();log.error("删除对象失败");}}/** * 根据主键删除对象 */public void removeObject(Class clazz, Serializable id){Session session = getSession();Transaction tx = beginTransaction(session);try{session.delete(getObject(clazz, id));tx.commit();}catch(Exception e){tx.rollback();log.error("根据主键删除对象失败");}}/** * 创建事务 */private Transaction beginTransaction(Session session){return session.beginTransaction();}}

 

 HibernateSessionFactory.java

package com.ajax.core;import org.hibernate.HibernateException;import org.hibernate.Session;import org.hibernate.cfg.AnnotationConfiguration;import org.hibernate.cfg.Configuration;/** * Configures and provides access to Hibernate sessions, tied to the * current thread of execution. Follows the Thread Local Session * pattern, see {@link http://hibernate.org/42.html }. */public class HibernateSessionFactory { /** * Location of hibernate.cfg.xml file. * Location should be on the classpath as Hibernate uses * #resourceAsStream style lookup for its configuration file. * The default classpath location of the hibernate config file is * in the default package. Use #setConfigFile() to update * the location of the configuration file for the current session. */ private static String CONFIG_FILE_LOCATION = "/hibernate.cfg.xml";private static final ThreadLocal<Session> threadLocal = new ThreadLocal<Session>(); private static AnnotationConfiguration configuration = new AnnotationConfiguration(); //这里需要修改 private static org.hibernate.SessionFactory sessionFactory; private static String configFile = CONFIG_FILE_LOCATION;static { try {configuration.configure(configFile);sessionFactory = configuration.buildSessionFactory();} catch (Exception e) {System.err.println("%%%% Error Creating SessionFactory %%%%");e.printStackTrace();} } private HibernateSessionFactory() { }/** * Returns the ThreadLocal Session instance. Lazy initialize * the <code>SessionFactory</code> if needed. * * @return Session * @throws HibernateException */ public static Session getSession() throws HibernateException { Session session = (Session) threadLocal.get();if (session == null || !session.isOpen()) {if (sessionFactory == null) {rebuildSessionFactory();}session = (sessionFactory != null) ? sessionFactory.openSession(): null;threadLocal.set(session);} return session; }/** * Rebuild hibernate session factory * */public static void rebuildSessionFactory() {try {configuration.configure(configFile);sessionFactory = configuration.buildSessionFactory();} catch (Exception e) {System.err.println("%%%% Error Creating SessionFactory %%%%");e.printStackTrace();}}/** * Close the single hibernate session instance. * * @throws HibernateException */ public static void closeSession() throws HibernateException { Session session = (Session) threadLocal.get(); threadLocal.set(null); if (session != null) { session.close(); } }/** * return session factory * */public static org.hibernate.SessionFactory getSessionFactory() {return sessionFactory;}/** * return session factory * *session factory will be rebuilded in the next call */public static void setConfigFile(String configFile) {HibernateSessionFactory.configFile = configFile;sessionFactory = null;}/** * return hibernate configuration * */public static Configuration getConfiguration() {return configuration;}}

 

由于使用到hibernate注解方式，所以这里在用到hibernate-annotations-3.3.0.jar和hibernate-commons-

annotations-3.0.0.jar包，还需要如下的包(具体的版本可以选择最新的):
asm-1.5.3.jar
cglib-2.1.3.jar
commons-collections-2.1.1.jar
commons-lang-2.1.jar
commons-logging-1.1.jar
dom4j-1.6.1.jar
hibernate3-3.2.5.jar
mysql-connector.jar

使用上面方式就可以构建简单的hibernate访问数据库了。