hibernate 延迟加载 数据调用

Question

我在做一个小的项目，锻炼一下自己。请问一下我用的是struts+hibernate，其中有的team(班级)和Student多对一的关系，team对班级设置的是延迟加载，当我在页面中调用team.getStudents()的时候提示session was closed,但是我用不想把student设置为立即加载，有什么办法能使调用team.getStudents()方法时打开session？
[b]问题补充：[/b]
谢谢以上两位的回答，我现在还想问一下，我想让原来的项目保持struts+hibernate保持不变想要实现对students的延迟调用是使用OpenSessionInView 好呢还是自己做一个filter好呢，那个更方便，具体的做法是怎样的？这是我帮别人做得网站，很急，希望高手们能帮一下，谢了！
[b]问题补充：[/b]
如果使用OpenSessionInView 该引入哪些jar包？我感觉这个问题是hibernate很大的一个缺陷啊，为什么hibernate自己不做一个jar包解决呢，而使用spring的，这样很麻烦那

Answer 1

给你粘出几个类的代码，你自己看看，
类HibernateUtil.java，用这个类来管理session和事务
[code="java"]
import org.hibernate.*;
import org.hibernate.cfg.Configuration;
import org.hibernate.exceptions.InfrastructureException;
import org.apache.commons.logging.*;

import javax.naming.*;

/**

• Basic Hibernate helper class, handles SessionFactory, Session and Transaction.
• Uses a static initializer for the initial SessionFactory creation
• and holds Session and Transactions in thread local variables. All
• exceptions are wrapped in an unchecked InfrastructureException. *

• @author [e-mail]
  */
  public class HibernateUtil {

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

  private static Configuration configuration;
  private static SessionFactory sessionFactory;
  private static final ThreadLocal threadSession = new ThreadLocal();
  private static final ThreadLocal threadTransaction = new ThreadLocal();
  private static final ThreadLocal threadInterceptor = new ThreadLocal();

  // Create the initial SessionFactory from the default configuration files
  static {
  try {
  configuration = new Configuration();
  sessionFactory = configuration.configure().buildSessionFactory();
  // We could also let Hibernate bind it to JNDI:
  // configuration.configure().buildSessionFactory()
  } catch (Throwable ex) {
  // We have to catch Throwable, otherwise we will miss
  // NoClassDefFoundError and other subclasses of Error
  log.error("Building SessionFactory failed.", ex);
  throw new ExceptionInInitializerError(ex);
  }
  }

  /**

  • Returns the SessionFactory used for this static class. *
  • @return SessionFactory / public static SessionFactory getSessionFactory() { / Instead of a static variable, use JNDI: SessionFactory sessions = null; try { Context ctx = new InitialContext(); String jndiName = "java:hibernate/HibernateFactory"; sessions = (SessionFactory)ctx.lookup(jndiName); } catch (NamingException ex) { throw new InfrastructureException(ex); } return sessions; */ return sessionFactory; }

  /**

  • Returns the original Hibernate configuration. *
  • @return Configuration */ public static Configuration getConfiguration() { return configuration; }

  /**

  • Rebuild the SessionFactory with the static Configuration. * */ public static void rebuildSessionFactory() throws InfrastructureException { synchronized(sessionFactory) { try { sessionFactory = getConfiguration().buildSessionFactory(); } catch (Exception ex) { throw new InfrastructureException(ex); } } }

  /**

  • Rebuild the SessionFactory with the given Hibernate Configuration. *
  • @param cfg */ public static void rebuildSessionFactory(Configuration cfg) throws InfrastructureException { synchronized(sessionFactory) { try { sessionFactory = cfg.buildSessionFactory(); configuration = cfg; } catch (Exception ex) { throw new InfrastructureException(ex); } } }

  /**

  • Retrieves the current Session local to the thread.
  • If no Session is open, opens a new Session for the running thread. *
  • @return Session */ public static Session getSession() throws InfrastructureException { Session s = (Session) threadSession.get(); try { if (s == null) { log.debug("Opening new Session for this thread."); if (getInterceptor() != null) { log.debug("Using interceptor: " + getInterceptor().getClass()); s = getSessionFactory().openSession(getInterceptor()); } else { s = getSessionFactory().openSession(); } threadSession.set(s); } } catch (HibernateException ex) { throw new InfrastructureException(ex); } return s; }

  /**

  • Closes the Session local to the thread. */ public static void closeSession() throws InfrastructureException { try { Session s = (Session) threadSession.get(); threadSession.set(null); if (s != null && s.isOpen()) { log.debug("Closing Session of this thread."); s.close(); } } catch (HibernateException ex) { throw new InfrastructureException(ex); } }

  /**

  • Start a new database transaction. */ public static void beginTransaction() throws InfrastructureException { Transaction tx = (Transaction) threadTransaction.get(); try { if (tx == null) { log.debug("Starting new database transaction in this thread."); tx = getSession().beginTransaction(); threadTransaction.set(tx); } } catch (HibernateException ex) { throw new InfrastructureException(ex); } }

  /**

  • Commit the database transaction. */ public static void commitTransaction() throws InfrastructureException { Transaction tx = (Transaction) threadTransaction.get(); try { if ( tx != null && !tx.wasCommitted() && !tx.wasRolledBack() ) { log.debug("Committing database transaction of this thread."); tx.commit(); } threadTransaction.set(null); } catch (HibernateException ex) { rollbackTransaction(); throw new InfrastructureException(ex); } }

  /**

  • Commit the database transaction. */ public static void rollbackTransaction() throws InfrastructureException { Transaction tx = (Transaction) threadTransaction.get(); try { threadTransaction.set(null); if ( tx != null && !tx.wasCommitted() && !tx.wasRolledBack() ) { log.debug("Tyring to rollback database transaction of this thread."); tx.rollback(); } } catch (HibernateException ex) { throw new InfrastructureException(ex); } finally { closeSession(); } }

  /**

  • Reconnects a Hibernate Session to the current Thread. *
  • @param session The Hibernate Session to be reconnected. */ public static void reconnect(Session session) throws InfrastructureException { try { session.reconnect(); threadSession.set(session); } catch (HibernateException ex) { throw new InfrastructureException(ex); } }

  /**

  • Disconnect and return Session from current Thread. *

  • @return Session the disconnected Session
    */
    public static Session disconnectSession()
    throws InfrastructureException {

    Session session = getSession();
    try {
    threadSession.set(null);
    if (session.isConnected() && session.isOpen())
    session.disconnect();
    } catch (HibernateException ex) {
    throw new InfrastructureException(ex);
    }
    return session;
    }

  /**

  • Register a Hibernate interceptor with the current thread.
  • Every Session opened is opened with this interceptor after
  • registration. Has no effect if the current Session of the
  • thread is already open, effective on next close()/getSession(). */ public static void registerInterceptor(Interceptor interceptor) { threadInterceptor.set(interceptor); }

  private static Interceptor getInterceptor() {
  Interceptor interceptor =
  (Interceptor) threadInterceptor.get();
  return interceptor;
  }

}

[/code]