public ArrayList querryRecord() {
		String sql = "select * from traderecord";
		ArrayList recordList = null;
		conn = manager.getConnection();
		try {
			stmt = conn.createStatement();
			rs = stmt.executeQuery(sql);
			recordList = new ArrayList();
			
			while(rs.next()) {
				TradeRecord tr = new TradeRecord();
				tr.setId(rs.getInt(1));
				tr.setUserId(rs.getInt(2));
				tr.setBookId(rs.getInt(3));
				tr.setTradeNum(rs.getInt(4));
				tr.setSum(rs.getDouble(5));
				recordList.add(tr);
			}
			return recordList;
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			manager.closeAll(rs,stmt,conn);
			return recordList;
		}
	}