jsp三级菜单栏

// 示例代码：数据库查询
String sql = "SELECT * FROM menu WHERE parent_id = ?";
try (Connection conn = DriverManager.getConnection(url, username, password);
     PreparedStatement pstmt = conn.prepareStatement(sql)) {
    pstmt.setInt(1, parentId);
    ResultSet rs = pstmt.executeQuery();
    while (rs.next()) {
        // 处理结果集
    }
} catch (SQLException e) {
    e.printStackTrace();
}

<!-- 示例代码：JavaScript控制菜单展开和折叠 -->
<script>
function toggleSubMenu(menuId) {
    var subMenu = document.getElementById(menuId);
    if (subMenu.style.display === "none") {
        subMenu.style.display = "block";
    } else {
        subMenu.style.display = "none";
    }
}
</script>

<ul>
    <li onclick="toggleSubMenu('submenu1')">主菜单1
        <ul id="submenu1" style="display:none;">
            <li>子菜单1-1</li>
            <li>子菜单1-2</li>
        </ul>
    </li>
</ul>

// 示例代码：分页查询
String sql = "SELECT * FROM menu WHERE parent_id = ? LIMIT ?, ?";
try (Connection conn = DriverManager.getConnection(url, username, password);
     PreparedStatement pstmt = conn.prepareStatement(sql)) {
    pstmt.setInt(1, parentId);
    pstmt.setInt(2, offset);
    pstmt.setInt(3, limit);
    ResultSet rs = pstmt.executeQuery();
    while (rs.next()) {
        // 处理结果集
    }
} catch (SQLException e) {
    e.printStackTrace();
}