SQLException:Object has closed

 String insertRecordSql="select distinct depcity,arrcity,cabin,flightdate from TM_download where id>="+startId;  DBConnection  con=new DBConnection();  ResultSet record=con.executeQuery(insertRecordSql);
con=null;
con=new DBConnection();
String cabin;
String airline;
String update;//="update TM_download set price=";
try{
    while(record.next()){
         update="update TM_download set price=";
         cabin=record.getString("cabin");
         String depcity=record.getString("depcity");
         String arrcity=record.getString("arrcity");
         java.sql.Date flightdate=record.getDate("flightdate");
         airline=depcity+"-"+arrcity;
         Float cabinDisCoutF=(Float)cabinDiscount.get(cabin);
         Integer airlinePriceInt=(Integer)airlinePrice.get(airline);
         int cabinPrice=0;
         if(cabinDisCoutF!=null)
                        cabinPrice=getCommonPrice(airlinePriceInt.intValue(),cabinDisCoutF.floatValue());
         else
             cabinPrice=getSpecialcabinPrice(cabin,flightdate);
                    update=update+cabinPrice+" where cabin='"+cabin+"' and depcity='"+depcity+"' and arrcity='"+arrcity+"' and id>="+startId;
             con.executeUpdate(update);
             System.out.println("calculateCabinPrice sql:"+update);
      }
}catch(SQLException sqle){
     sqle.printStackTrace();
}finally{
     con.close();
}

              程序缺少第3行时，整个while循环会执行一次，然后抛出Object  has closed 异常。具体原因还要进一步查证