private int getMaxidUsuario(){
		int max = 0;
		
		try {
			conn = PaginaWebConnectionFactory.getInstance().getConnection();
			String sql = "select MAX(id_usuario) as maximo from usuario";
			ps = conn.prepareStatement(sql);
			rs = ps.executeQuery();
			
			if (rs.next()){
				max = rs.getInt("maximo");
			}
			
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			try {
				if (conn != null)
					conn.close();
				if (ps != null)
					ps.close();
				if (rs != null)
					rs.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
		
		return max;
	}