hibernate入门小例子

昨天刚开始接触hibernate便被伤的彻底，连最简单的都不会配置，然后看书看网上的，要么是比较复杂，不适合刚入门的新手，要么太久了，代码有些地方不太正确

折磨到了今天才琢磨出一点，写这个帖子希望能够帮到像我一样的新手

#实验环境：myeclipse2013+mysql5.6.10+jdk1.7+hibernate 4.1

#目录结构：



#在mysql中新建一个名为hibernate的数据库

#首先，建立web应用，我用的是myeclispe2013，所以直接添加hibernate特性，如果用的是eclipse，则将下载的hibernate包中的lib目录下的required目录中的jar复制到应用中的lib目录下，然后buildpath.

接下来主要步骤：

1.修改src目录下的hibernate.cfg.xml，如果没有自动生成，则手动新建一个。修改如下

<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<!-- Generated by MyEclipse Hibernate Tools.                   -->
<hibernate-configuration>

<session-factory>
<!-- 表示可动态修改hibernate属性文件 -->
<property name="hbm2ddl.auto">update</property>
<!-- 表示用户使用的数据库种类 -->
<property name="dialect">org.hibernate.dialect.MySQL5Dialect</property>
<!-- 指定是否在控制台打印对应的SQL语句 -->
<property name="show_sql">true</property>
<!-- 链接数据库属性 -->
<property name="connection.url">jdbc:mysql://localhost:3306/hibernate</property>
<property name="connection.username">root</property>
<property name="connection.password">root</property>
<property name="connection.driver_class">com.mysql.jdbc.Driver</property>

<mapping resource="tbl/hibernate/bean/Person.hbm.xml"/>
</session-factory>

</hibernate-configuration>

2.新建一个简单的POJO(普通java对象类) Person

此处id用于被hibernate识别用于主键，相当于平时只有name属性的POJO

package tbl.hibernate.bean;

public class Person {
private Integer id;    //id是标识符，被hibernate识别
private String name;

public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}

}

3.新建Person.hbm.xml，修改如下

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- 指定包，可不指定，但这样可以稍微减少代码量 -->
<hibernate-mapping package="tbl.hibernate.bean">
<!-- 类名，如果上面未指定包，则此处需要在类之前将包写全，table对应数据库的表名 -->
<class name="Person" table="person">
<!--指定id为person类中的id，对应数据库表中的id列  -->
<id name="id" column="id">
<!-- 设置id为主键 -->
<generator class="identity"></generator>
</id>
<!-- 同上 -->
<property name="name" column="name"></property>
</class>
</hibernate-mapping>

4.建立HibernateUtil工具类，myeclipse可自动右键生成，NEW-->Hibernate Session Factory

package tbl.hibernate.util;

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;

/**
* 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 HibernateUtil {

/**
* 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 final ThreadLocal<Session> threadLocal = new ThreadLocal<Session>();
private static org.hibernate.SessionFactory sessionFactory;

private static Configuration configuration = new Configuration();
private static ServiceRegistry serviceRegistry;

static {
try {
configuration.configure();
serviceRegistry = new ServiceRegistryBuilder().applySettings(configuration.getProperties()).buildServiceRegistry();
sessionFactory = configuration.buildSessionFactory(serviceRegistry);
} catch (Exception e) {
System.err.println("%%%% Error Creating SessionFactory %%%%");
e.printStackTrace();
}
}
private HibernateUtil() {
}

/**
* 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();
serviceRegistry = new ServiceRegistryBuilder().applySettings(configuration.getProperties()).buildServiceRegistry();
sessionFactory = configuration.buildSessionFactory(serviceRegistry);
} 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 hibernate configuration
*
*/
public static Configuration getConfiguration() {
return configuration;
}

}

5.最后一步，建立一个测试文件Person_test

package tbl.hibernate.domain;

import org.hibernate.Session;

import tbl.hibernate.bean.Person;
import tbl.hibernate.util.HibernateUtil;

public class Person_test {
public static void main(String[] args) {
　　　　　//通过工具类获取Session
Session session = HibernateUtil.getSession();
　　　　 //开启事务
session.beginTransaction();
　　　　　//新建Person类，存入值
Person p = new Person();
p.setName("Tom");
　　　　　//将p存入session
session.save(p);
　　　　  //提交事务
session.getTransaction().commit();
　　　　　//关闭session
session.close();
}
}

#运行Person_test,如果没有报错，并且数据库中生成了一个person表，那么恭喜你，你成功了！

希望能够帮到大家，如果有什么疑问，可以评论，一起讨论。写的不对的也请大神指正，谢谢