<div class="form-group" th:if="${result == 5}"> 为什么result 等于5还是不显示？

可能是因为你的模板引擎没有正确解析Thymeleaf表达式。请确保你已经正确地配置了Thymeleaf，并且在模板中使用了正确的语法。你可以检查一下result的值是否真的等于5，或者尝试使用Thymeleaf的调试模式来查看表达式的解析结果。另外，你也可以尝试使用if-else语句来代替th:if，看看是否能够正常显示。

相关问题

thinkphp5实现无限级新闻分类

要实现无限级新闻分类，可以使用thinkphp5自带的树形结构扩展类库来实现。

1. 创建一个分类模型

在app\admin\model目录下创建一个NewsCategory.php模型文件。代码如下：

namespace app\admin\model;

use think\Model;
use think\Db;
use think\Tree;

class NewsCategory extends Model
{
    protected $name = 'news_category';

    public function getTree()
    {
        $list = Db::name($this->name)->order('sort_order')->select();
        $tree = new Tree();
        $tree->init($list);
        $tree = $tree->getTreeList($tree->getTreeArray(0), 'name');
        return $tree;
    }
}

2. 创建分类控制器

在app\admin\controller目录下创建一个NewsCategory.php控制器文件。代码如下：

namespace app\admin\controller;

use think\Controller;
use app\admin\model\NewsCategory as CategoryModel;

class NewsCategory extends Controller
{
    public function index()
    {
        $category_model = new CategoryModel();
        $tree = $category_model->getTree();
        $this->assign('tree', $tree);
        return $view->fetch();
    }

    public function add()
    {
        $category_model = new CategoryModel();
        $tree = $category_model->getTree();
        $this->assign('tree', $tree);
        return $view->fetch();
    }

    public function save()
    {
        $data = input('post.');
        $category_model = new CategoryModel();
        $result = $category_model->validate('NewsCategory')->save($data);
        if ($result === false) {
            $this->error($category_model->getError());
        } else {
            $this->success('添加成功', url('index'));
        }
    }

    public function edit($id)
    {
        $category_model = new CategoryModel();
        $category = $category_model->get($id);
        $tree = $category_model->getTree();
        $this->assign('tree', $tree);
        $this->assign('category', $category);
        return $view->fetch();
    }

    public function update($id)
    {
        $data = input('post.');
        $category_model = new CategoryModel();
        $result = $category_model->validate('NewsCategory')->save($data, ['id' => $id]);
        if ($result === false) {
            $this->error($category_model->getError());
        } else {
            $this->success('编辑成功', url('index'));
        }
    }

    public function delete($id)
    {
        $category_model = new CategoryModel();
        $category = $category_model->get($id);
        if (empty($category)) {
            $this->error('分类不存在');
        }
        $result = $category->delete();
        if ($result === false) {
            $this->error('删除失败');
        } else {
            $this->success('删除成功');
        }
    }
}

3. 创建分类列表视图

在app\admin\view\news_category目录下创建一个index.html视图文件。代码如下：

{extend name="layout/base"}

{block name="content"}
<div class="row">
    <div class="col-md-12">
        <div class="panel panel-default">
            <div class="panel-heading">
                <h3 class="panel-title">分类列表</h3>
            </div>
            <div class="panel-body">
                <table class="table table-striped table-bordered table-hover">
                    <thead>
                        <tr>
                            <th>ID</th>
                            <th>分类名称</th>
                            <th>排序</th>
                            <th>操作</th>
                        </tr>
                    </thead>
                    <tbody>
                        {volist name="tree" id="vo"}
                        <tr>
                            <td>{$vo.id}</td>
                            <td>{$vo.name}</td>
                            <td>{$vo.sort_order}</td>
                            <td>
                                <a href="{:url('edit', ['id' => $vo.id])}" class="btn btn-xs btn-primary"><i class="fa fa-edit"></i> 编辑</a>
                                <a href="{:url('delete', ['id' => $vo.id])}" class="btn btn-xs btn-danger confirm"><i class="fa fa-trash"></i> 删除</a>
                            </td>
                        </tr>
                        {/volist}
                    </tbody>
                </table>
            </div>
        </div>
    </div>
</div>
{/block}

4. 创建分类添加/编辑视图

在app\admin\view\news_category目录下创建一个add.html和edit.html视图文件。代码如下：

add.html

{extend name="layout/base"}

{block name="content"}
<div class="row">
    <div class="col-md-12">
        <div class="panel panel-default">
            <div class="panel-heading">
                <h3 class="panel-title">添加分类</h3>
            </div>
            <div class="panel-body">
                <form role="form" method="post" action="{:url('save')}">
                    <div class="form-group">
                        <label for="name">分类名称</label>
                        <input type="text" class="form-control" name="name" id="name" placeholder="请输入分类名称" required>
                    </div>
                    <div class="form-group">
                        <label for="parent_id">上级分类</label>
                        <select class="form-control" name="parent_id" id="parent_id">
                            <option value="0">顶级分类</option>
                            {volist name="tree" id="vo"}
                            <option value="{$vo.id}">{$vo.title}</option>
                            {/volist}
                        </select>
                    </div>
                    <div class="form-group">
                        <label for="sort_order">排序</label>
                        <input type="text" class="form-control" name="sort_order" id="sort_order" placeholder="请输入排序" required>
                    </div>
                    <button type="submit" class="btn btn-primary">添加</button>
                    <button type="reset" class="btn btn-default">重置</button>
                </form>
            </div>
        </div>
    </div>
</div>
{/block}

edit.html

{extend name="layout/base"}

{block name="content"}
<div class="row">
    <div class="col-md-12">
        <div class="panel panel-default">
            <div class="panel-heading">
                <h3 class="panel-title">编辑分类</h3>
            </div>
            <div class="panel-body">
                <form role="form" method="post" action="{:url('update', ['id' => $category->id])}">
                    <div class="form-group">
                        <label for="name">分类名称</label>
                        <input type="text" class="form-control" name="name" id="name" placeholder="请输入分类名称" value="{$category->name}" required>
                    </div>
                    <div class="form-group">
                        <label for="parent_id">上级分类</label>
                        <select class="form-control" name="parent_id" id="parent_id">
                            <option value="0">顶级分类</option>
                            {volist name="tree" id="vo"}
                            <option value="{$vo.id}" {if condition="$category->parent_id == $vo.id"}selected{/if}>{$vo.title}</option>
                            {/volist}
                        </select>
                    </div>
                    <div class="form-group">
                        <label for="sort_order">排序</label>
                        <input type="text" class="form-control" name="sort_order" id="sort_order" placeholder="请输入排序" value="{$category->sort_order}" required>
                    </div>
                    <button type="submit" class="btn btn-primary">保存</button>
                    <button type="reset" class="btn btn-default">重置</button>
                </form>
            </div>
        </div>
    </div>
</div>
{/block}

5. 创建分类验证器

在app\admin\validate目录下创建一个NewsCategory.php验证器文件。代码如下：

namespace app\admin\validate;

use think\Validate;

class NewsCategory extends Validate
{
    protected $rule = [
        'name' => 'require|max:50',
        'parent_id' => 'integer',
        'sort_order' => 'integer',
    ];

    protected $message = [
        'name.require' => '分类名称不能为空',
        'name.max' => '分类名称不能超过50个字符',
        'parent_id.integer' => '上级分类ID必须是整数',
        'sort_order.integer' => '排序必须是整数',
    ];

    protected $scene = [
        'save' => ['name', 'parent_id', 'sort_order'],
        'update' => ['name', 'parent_id', 'sort_order'],
    ];
}

6. 创建分类数据表

在数据库中创建一个news_category表，包含id、name、parent_id、sort_order四个字段。其中，parent_id为0表示顶级分类，非0表示上级分类的id。

至此，无限级新闻分类的实现就完成了。

利用web开发一段网吧管理系统代码

这里提供一个简单的网吧管理系统的代码，包括基本的登录、注册、添加机器、删除机器、显示机器等功能。

前端使用HTML、CSS、JavaScript和Bootstrap框架，后端使用PHP和MySQL数据库。

1. 登录页面（login.html）

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>网吧管理系统 - 登录</title>
    <link rel="stylesheet" href="https://cdn.bootcss.com/bootstrap/3.3.7/css/bootstrap.min.css">
    <script src="https://cdn.bootcss.com/jquery/3.4.1/jquery.min.js"></script>
    <script src="https://cdn.bootcss.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
</head>
<body>
<div class="container">
    <h2>网吧管理系统 - 登录</h2>
    <form class="form-horizontal" action="login.php" method="post">
        <div class="form-group">
            <label class="control-label col-sm-2" for="username">用户名:</label>
            <div class="col-sm-10">
                <input type="text" class="form-control" id="username" placeholder="请输入用户名" name="username">
            </div>
        </div>
        <div class="form-group">
            <label class="control-label col-sm-2" for="password">密码:</label>
            <div class="col-sm-10">
                <input type="password" class="form-control" id="password" placeholder="请输入密码" name="password">
            </div>
        </div>
        <div class="form-group">
            <div class="col-sm-offset-2 col-sm-10">
                <button type="submit" class="btn btn-default">登录</button>
                <a href="register.html" class="btn btn-primary">注册</a>
            </div>
        </div>
    </form>
</div>
</body>
</html>

2. 注册页面（register.html）

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>网吧管理系统 - 注册</title>
    <link rel="stylesheet" href="https://cdn.bootcss.com/bootstrap/3.3.7/css/bootstrap.min.css">
    <script src="https://cdn.bootcss.com/jquery/3.4.1/jquery.min.js"></script>
    <script src="https://cdn.bootcss.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
</head>
<body>
<div class="container">
    <h2>网吧管理系统 - 注册</h2>
    <form class="form-horizontal" action="register.php" method="post">
        <div class="form-group">
            <label class="control-label col-sm-2" for="username">用户名:</label>
            <div class="col-sm-10">
                <input type="text" class="form-control" id="username" placeholder="请输入用户名" name="username">
            </div>
        </div>
        <div class="form-group">
            <label class="control-label col-sm-2" for="password">密码:</label>
            <div class="col-sm-10">
                <input type="password" class="form-control" id="password" placeholder="请输入密码" name="password">
            </div>
        </div>
        <div class="form-group">
            <div class="col-sm-offset-2 col-sm-10">
                <button type="submit" class="btn btn-default">注册</button>
            </div>
        </div>
    </form>
</div>
</body>
</html>

3. 添加机器页面（add.html）

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>网吧管理系统 - 添加机器</title>
    <link rel="stylesheet" href="https://cdn.bootcss.com/bootstrap/3.3.7/css/bootstrap.min.css">
    <script src="https://cdn.bootcss.com/jquery/3.4.1/jquery.min.js"></script>
    <script src="https://cdn.bootcss.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
</head>
<body>
<div class="container">
    <h2>网吧管理系统 - 添加机器</h2>
    <form class="form-horizontal" action="add.php" method="post">
        <div class="form-group">
            <label class="control-label col-sm-2" for="name">机器名称:</label>
            <div class="col-sm-10">
                <input type="text" class="form-control" id="name" placeholder="请输入机器名称" name="name">
            </div>
        </div>
        <div class="form-group">
            <label class="control-label col-sm-2" for="ip">IP地址:</label>
            <div class="col-sm-10">
                <input type="text" class="form-control" id="ip" placeholder="请输入IP地址" name="ip">
            </div>
        </div>
        <div class="form-group">
            <div class="col-sm-offset-2 col-sm-10">
                <button type="submit" class="btn btn-default">添加</button>
            </div>
        </div>
    </form>
</div>
</body>
</html>

4. 删除机器页面和显示机器页面（delete.php和index.php）

<!-- delete.php -->
<?php
require_once 'common.php';

$id = $_GET['id'];
$sql = "DELETE FROM machine WHERE id=$id";
$result = mysqli_query($conn, $sql);
if ($result) {
    header('Location: index.php');
} else {
    echo "Error deleting record: " . mysqli_error($conn);
}
mysqli_close($conn);
?>

<!-- index.php -->
<?php
require_once 'common.php';

$sql = "SELECT * FROM machine";
$result = mysqli_query($conn, $sql);
?>
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>网吧管理系统 - 机器列表</title>
    <link rel="stylesheet" href="https://cdn.bootcss.com/bootstrap/3.3.7/css/bootstrap.min.css">
    <script src="https://cdn.bootcss.com/jquery/3.4.1/jquery.min.js"></script>
    <script src="https://cdn.bootcss.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
</head>
<body>
<div class="container">
    <h2>网吧管理系统 - 机器列表</h2>
    <a href="add.html" class="btn btn-primary">添加机器</a>
    <table class="table table-striped">
        <thead>
        <tr>
            <th>ID</th>
            <th>机器名称</th>
            <th>IP地址</th>
            <th>操作</th>
        </tr>
        </thead>
        <tbody>
        <?php
        if (mysqli_num_rows($result) > 0) {
            while ($row = mysqli_fetch_assoc($result)) {
                echo "<tr>";
                echo "<td>".$row['id']."</td>";
                echo "<td>".$row['name']."</td>";
                echo "<td>".$row['ip']."</td>";
                echo "<td><a href='delete.php?id=".$row['id']."'>删除</a></td>";
                echo "</tr>";
            }
        }
        ?>
        </tbody>
    </table>
</div>
</body>
</html>

5. 登录、注册、添加机器、删除机器的PHP代码（login.php、register.php、add.php）

<!-- common.php -->
<?php
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "webcafe";

$conn = mysqli_connect($servername, $username, $password, $dbname);
if (!$conn) {
    die("Connection failed: " . mysqli_connect_error());
}
?>

<!-- login.php -->
<?php
require_once 'common.php';

$username = $_POST['username'];
$password = $_POST['password'];
$sql = "SELECT * FROM user WHERE username='$username' AND password='$password'";
$result = mysqli_query($conn, $sql);
if (mysqli_num_rows($result) > 0) {
    header('Location: index.php');
} else {
    echo "用户名或密码错误";
}
mysqli_close($conn);
?>

<!-- register.php -->
<?php
require_once 'common.php';

$username = $_POST['username'];
$password = $_POST['password'];
$sql = "INSERT INTO user (username, password) VALUES ('$username', '$password')";
$result = mysqli_query($conn, $sql);
if ($result) {
    header('Location: login.html');
} else {
    echo "Error: " . $sql . "<br>" . mysqli_error($conn);
}
mysqli_close($conn);
?>

<!-- add.php -->
<?php
require_once 'common.php';

$name = $_POST['name'];
$ip = $_POST['ip'];
$sql = "INSERT INTO machine (name, ip) VALUES ('$name', '$ip')";
$result = mysqli_query($conn, $sql);
if ($result) {
    header('Location: index.php');
} else {
    echo "Error: " . $sql . "<br>" . mysqli_error($conn);
}
mysqli_close($conn);
?>

这样一个简单的网吧管理系统就完成了。需要注意的是，这里只提供了基本的功能，实际应用中需要考虑更多的安全性和可靠性问题。