php/app/common/middleware/InstallMiddleware.php

<?php
/**
 * @package merchant
 *
 * @author xaboy
 * @day 2020-03-26
 *
 *
 */

namespace app\common\middleware;


use app\Request;
use think\exception\HttpResponseException;
use think\facade\Route;
use think\Response;

class InstallMiddleware extends BaseMiddleware
{

    public function before(Request $request)
    {
        // 系统维护开关（示例条件，实际应根据配置）
        $isMaintenance = false; // 改为从配置读取

        if ($isMaintenance) {
            // 创建符合前端格式的响应
            $response = json([
                'status' => 400,
                'message' => '系统正在升级中'
            ], 503); // 使用503状态码表示服务不可用

            // 抛出异常中断请求
            throw new HttpResponseException($response);
        }
        if(!file_exists(__DIR__.'/../../../install/install.lock')){
            throw new HttpResponseException( Response::create('/install.html', 'redirect')->code(302));
        }
    }

    public function after(Response $response)
    {
    }
}