getGeneratedKeys（）返回自增主键值

public void add(Category bean) {

        String sql = "insert into category values(null,?)";
        try (Connection c = DBUtil.getConnection(); PreparedStatement ps = c.prepareStatement(sql)) {

            ps.setString(1, bean.getName());

            ps.execute();

            ResultSet rs = ps.getGeneratedKeys();
            if (rs.next()) {
                int id = rs.getInt(1);
                bean.setId(id);
            }
        } catch (SQLException e) {

            e.printStackTrace();
        }
    }
public void add(Category bean) {

        S