怎么无法将数据写入数据库内啊，请各位帮忙看一下！！谢谢

public class WriteLog {
     public static SessionFactory sf;
     static{
     try{
        Configuration conf=new Configuration().configure();
        sf= conf.buildSessionFactory();
     }catch(Exception e){
         e.printStackTrace();
        
     }finally{
     }
     }
     public void WriteLogToDB(String contents) throws SystemException, HeuristicMixedException, RollbackException, HeuristicRollbackException{
        Contents con=new Contents();
        con.setLogcontent(contents);
        con.setLogdate(new Date());
        Session session=sf.getCurrentSession();
        Transaction tran=null;
        try{
            tran=(Transaction) session.beginTransaction();
            session.save(con);
            tran.commit();
        }catch(HibernateException e){
           if(tran!=null)tran.rollback();
            
           throw e;
        }finally{
        session.close();
        }
     }