hibernatesessionfactory.java

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package com.zjxy.hibernate;

import org.hibernate.HibernateException;
import org.hibernate.Session;
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. NOTICE: Location should be on the
	 * classpath as Hibernate uses #resourceAsStream style lookup for its
	 * configuration file. That is place the config file in a Java package - the
	 * default location is the default Java package.<br>
	 * <br>
	 * Examples: <br>
	 * <code>CONFIG_FILE_LOCATION = "/hibernate.conf.xml". 
	 * CONFIG_FILE_LOCATION = "/com/foo/bar/myhiberstuff.conf.xml".</code>
	 */
	private static String CONFIG_FILE_LOCATION = "/hibernate.cfg.xml";

	/** Holds a single instance of Session */
	private static final ThreadLocal threadLocal = new ThreadLocal();

	/** The single instance of hibernate configuration */
	private static final Configuration cfg = new Configuration();

	/** The single instance of hibernate SessionFactory */
	private static org.hibernate.SessionFactory sessionFactory;

	/**
	 * Returns the ThreadLocal Session instance. Lazy initialize the
	 * <code>SessionFactory</code> if needed.
	 * 
	 * @return Session
	 * @throws HibernateException
	 */
	public static Session currentSession() throws HibernateException {
		Session session = (Session) threadLocal.get();

		if (session == null) {
			if (sessionFactory == null) {
				try {
					cfg.configure(CONFIG_FILE_LOCATION);
					sessionFactory = cfg.buildSessionFactory();
				} catch (Exception e) {
					System.err
							.println("%%%% Error Creating SessionFactory %%%%");
					e.printStackTrace();
				}
			}
			session = sessionFactory.openSession();
			threadLocal.set(session);
		}

		return session;
	}

	/**
	 * 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();
		}
	}

	/**
	 * Default constructor.
	 */
	private HibernateSessionFactory() {
	}

}