import org.hibernate.*;   
      
    import org.hibernate.cfg.*;   
      
    public class CoreSession {   
      
    static SessionFactory sessionFactory;   
    //注意到这里的SessionFactory都是static的
    //初始化Hibernate,创建SessionFactory实例,只在该类被加载到内存时执行一次   
      
    static{   
      
        try{   
      
             Configuration config = new Configuration().configure();   
      
             sessionFactory = config.buildSessionFactory();   
      
        } catch (Exception e) {   
      
            System.out.println(e.getMessage());   
      
        }   
      
    }   
      
    }   

public class CoreSession {   
      
   private static SessionFactory sessionFactory;   
   public static SessionFactory getSessionFactory(){
       if(sessionFactory == null) {
             try{   
                 Configuration config = new Configuration().configure();  
                 sessionFactory = config.buildSessionFactory();         
             } catch (Exception e) {         
                 e.printStackTrace();
             }
        }
        return sessionFactory;

   }
}

------解决方案--------------------

static {}静态块代码会在classloader加载这个类的时候就被执行了,所以在使用时候完全可以放心,不用担心它没有被初始化的问题!

------解决方案--------------------
Java code
package dao;

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

public class SessionFactory {

    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 SessionFactory() {
    }

    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;
    }

    public static void rebuildSessionFactory() {
        try {
            configuration.configure(configFile);
            sessionFactory = configuration.buildSessionFactory();
        } catch (Exception e) {
            System.err.println("%%%% Error Creating SessionFactory %%%%");
            e.printStackTrace();
        }
    }

    public static void closeSession() {
        Session session = null;
        try {
            session = (Session) threadLocal.get();
            threadLocal.set(null);
            if (session != n