hibernate BaseDao的几个方法

package com.happybolin.mytest;

import java.util.List;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.hibernate.HibernateException;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.Transaction;

public class AbstractDao {
private Session session;

private Transaction tr;

private Log log = LogFactory.getLog(AbstractDao.class);

public AbstractDao() {
   HibernateUtil.buildSessionFactory();
}

protected void saveorUpdate(Object obj) {
   try {
    startOperation();
    session.saveOrUpdate(obj);
    tr.commit();
   } catch (HibernateException e) {
    log.error("saveorUpdate is fault");
   } finally {
    HibernateUtil.close(session);
   }
}

protected void delete(Object obj) {
   try {
    startOperation();
    session.delete(obj);
    tr.commit();
   } catch (HibernateException e) {
    log.error("could not delete ");
   } finally {
    HibernateUtil.close(session);
   }
}

protected Object find(Class clazz, Long id) {
   Object obj = null;
   try {
    startOperation();
    obj = session.load(clazz, id);
   } catch (HibernateException e) {
    log.error("find is fault");
   } finally {
    HibernateUtil.close(session);
   }
   return obj;
}

protected List findAll(Class clazz) {
   List objects = null;
   try {
    startOperation();
    Query query = session.createQuery("from clazz.getName");
    objects = query.list();
    tr.commit();
   } catch (HibernateException e) {
    log.error("findAll is fault");
   } finally {
    HibernateUtil.close(session);
   }
   return objects;
}

protected void startOperation() throws HibernateException {
   session = HibernateUtil.openSession();
   tr = session.beginTransaction();
}

}