sql 保存错误

   String jhsj =request.getParameter("jhsj");
      String jhbm =request.getParameter("jhbm");
      String jhr =request.getParameter("jhr");
      String jhnr =request.getParameter("jhnr");
      DoradoContext context=DoradoContext.getContext();
      Connection conn = ConnectionHelper.getDefaultConnection();
      PreparedStatement st = null;
      //ResultSet rs = null;
      String sql="insert into DT_KTGL_JHBZ(jhsj,jhbm,jhr,jhnr) values(to_date('"+jhsj+"','yyyy-mm-dd'),'"+jhbm+"','"+jhr+"','"+jhnr+"');";
      try{
       st=conn.prepareStatement(sql);
       out.print(sql);
       //st.execute();
      
      }finally{
         conn.close(); 
      }