hibernate多对多的关系实例

package org.hibernate; import java.io.Serializable; import org.hibernate.HibernateException; import org.hibernate.Session; import org.hibernate.cfg.Configuration; public class HibernateSessionFactory { 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 { //初使化时执行一次，以后就不会执行了！ try { configuration.configure(configFile); //解析hibernate.cfg.xml映射文件。 sessionFactory = configuration.buildSessionFactory(); } catch (Exception e) { System.err .println("%%%% Error Creating SessionFactory %%%%"); e.printStackTrace(); } } private HibernateSessionFactory() { //不能new } 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() throws HibernateException { Session session = (Session) threadLocal.get(); threadLocal.set(null); if (session != null) { session.close(); } } public static org.hibernate.SessionFactory getSessionFactory() { return sessionFactory; } public static void setConfigFile(String configFile) { HibernateSessionFactory.configFile = configFile; sessionFactory = null; } public static Configuration getConfiguration() { return configuration; } //增加对象 public static void add(Object entity){ Session s=null; Transaction tx=null; try{ s=HibernateSessionFactory.getSession(); tx=s.beginTransaction(); s.save(entity); tx.commit(); }finally{ if(s!=null){ s.close(); } } } //更新对象 public static void update(Object entity){ Session s=null; Transaction tx=null; try{ s=HibernateSessionFactory.getSession(); tx=s.beginTransaction(); s.update(entity); tx.commit(); }finally{ if(s!=null){ s.close(); } } } //删除对象 public static void delete(Object entity){ Session s=null; Transaction tx=null; try{ s=HibernateSessionFactory.getSession(); tx=s.beginTransaction(); s.delete(entity); tx.commit(); }finally{ if(s!=null){ s.close(); } } } //通过id得到对象 public static Object get(Class clazz,Serializable id){ Session s=null; try{ s=HibernateSessionFactory.getSession(); Object obj=s.get(clazz, id); return obj; }finally{ if(s!=null){ s.close(); } } } }