在jsp中定义session出错？在线等！

Question

<%@ page session=true %>
         <%       
        Random random=new Random();    
String   roomid="";   
  for(int j=0;j<8;j++){   
  int number=random.nextInt(10);   
  roomid=roomid.concat(new Integer(number).toString());  
  }
out.println(roomid);
System.out.println(roomid);
    room room=new room();
String sql="insert into room(roomid)values('"+roomid+"')"; 
    room.setRoomid(roomid);
    DataBase db = new DataBase();
db.executeUpdate(sql);
session.setAttribute("room",room);
%>