public static String checkUser(String u_name, String u_pwd) {
		String result = null;
		Connection con = DBUtil.getConnection();
		Statement st = null;
		ResultSet rs = null;
		try {
			st = con.createStatement();// 创建语句
			rs = st.executeQuery("select uid from mstx_user where u_name = '" + u_name + "' and u_pwd = '" + u_pwd + "';");
			if (rs.next()) {
				result = rs.getString(1);
			}
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			try {
				if (rs != null) {
					rs.close();
					rs = null;
				}
			} catch (Exception e) {
				e.printStackTrace();
			}
			try {
				if (st != null) {
					st.close();
					st = null;
				}
			} catch (Exception e) {
				e.printStackTrace();
			}
			try {
				if (con != null) {
					con.close();
					con = null;
				}
			} catch (Exception e) {
				e.printStackTrace();
			}
		}
		return result;
	}