HibernateUtil

import org.hibernate.*;
import org.hibernate.cfg.*;
import org.hibernate.service.*;
import org.hibernate.boot.registry.*;

/**
 * 该工具类提供了一个属性：SessionFactory sessionFactory
 * 并创建了sessionFactory 将它设置成static 这样其他程序就可以直接通过此工具类引用
 * 提供了二个方法:
 * 1：通过线程创建Session-->currentSession()
 * 2：关闭Session-->closeSession()
 * 需要在主类中手动关闭sessionFactory
 */
public class HibernateUtil {
 ???public static final SessionFactory sessionFactory;
 ???//创建sessionFactory
 ???static
 ???{
 ???????try
 ???????{
 ???????????// 采用默认的hibernate.cfg.xml来启动一个Configuration的实例
 ???????????Configuration cfg = new Configuration()
 ???????????????????.configure();
 ???????????// 以Configuration实例来创建SessionFactory实例
 ???????????ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder()
 ???????????????????.applySettings(cfg.getProperties()).build();
 ???????????sessionFactory = cfg.buildSessionFactory(serviceRegistry);
 ???????}
 ???????catch (Throwable ex)
 ???????{
 ???????????System.err.println("Initial SessionFactory creation failed." + ex);
 ???????????throw new ExceptionInInitializerError(ex);
 ???????}
 ???}

 ???// ThreadLocal可以隔离多个线程的数据共享，因此不再需要对线程同步
 ???public static final ThreadLocal<Session> session
 ???????????= new ThreadLocal<Session>();
 ???//创建Session
 ???public static Session currentSession()
 ???????????throws HibernateException
 ???{
 ???????//通过线程对象.get()方法安全创建Session
 ???????Session s = session.get();
 ???????// 如果该线程还没有Session,则创建一个新的Session
 ???????if (s == null)
 ???????{
 ???????????s = sessionFactory.openSession();
 ???????????// 将获得的Session变量存储在ThreadLocal变量session里
 ???????????session.set(s);
 ???????}
 ???????return s;
 ???}
 ???//关闭Session
 ???public static void closeSession()
 ???????????throws HibernateException
 ???{
 ???????Session s = session.get();
 ???????if (s != null)
 ???????????s.close();
 ???????session.set(null);
 ???}
}