HibernateUtil范例

HibernateUtil往往是用来生成SessionFactory以及getSession与closeSession的，主要是几个静态方法。

一、使用ThreadLocal隔离执行所使用的数据，避开Session多线程之间数据共享问题，主要是几个静态方法：

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class HibernateUtil {
private static final Log log=LogFactory.getLog(HibernateUtil.class);

private static final SessionFactory sessionFactory;
static
{
        try{
              sessionFactory=new Configuration().configure().buildSessionFactory();
   
       }catch(Throwable ex)
       {
              log.error("Initial SessionFactory creation failed.",ex);
              throw new ExceptionInInitializerError(ex);
       }
}
public static final ThreadLocal thread_var=new ThreadLocal();

public static Session currentSession()
{
      Session s=(Session)thread_var.get();
       if(s==null)
      {
        s=sessionFactory.openSession();
          thread_var.set(s);
    }
     return s;
}

public static void closeSession()
{
       Session s=(Session)thread_var.get();
      if(s!=null)
              s.close();
       thread_var.set(null);
}
}

二、不使用ThreadLocal的：

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class HibernateUtil {

    private static final SessionFactory sessionFactory;

    static {
        try {
            sessionFactory = new Configuration().configure()
                    .buildSessionFactory();
        } catch (HibernateException ex) {
            throw new RuntimeException("Exception building SessionFactory: "
                    + ex.getMessage(), ex);
        }
    }

    public static Session currentSession() throws HibernateException {
        Session s = sessionFactory.openSession();
        return s;
    }

    public static void closeSession(Session s) {
        s.close();
    }
}

三、用MyEclipse自动生成的HibernateUtil：

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.
     * 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 Configuration configuration = new Configuration();    
    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;
}

}