Laravel 路由中间件

路由中间件是用户和请求的中间层。通过用户登录来说明，这意味着当用户请求服务器时，请求将先通过中间件，然后中间件验证请求是否经过身份验证，如果用户的请求通过了身份验证，则该请求被发送到后端。 如果用户请求未通过身份验证，则中间件会将用户重定向到登录页面。

laravel中间件可用于参数校验，CSRF，权限校验等。这些中间件都位于 app/Http/Middleware 目录下。

以下讲解laravel中间件的创建和使用方法。

创建中间件

命令如下：

php artisan make:middleware '中间件名'

上面的例子中创建了一个CheckAge的中间件名称。要查看是否创建成功，可以转到中间件的路径 

d:\test\yxjc123\app\Http\Middleware

查看CheckAge.php文件是否生成。

使用中间件

中间件作用于所有的url路由。
1. 打开kernel.php 文件（D:\test\yxjc123\app\Http\Kernel.php）。在 middleware 和 routeMiddleware 数组中添加 CheckAge类，完整代码如下。

<?php

namespace App\Http;

use App\Http\Middleware\CheckAge;
use Illuminate\Foundation\Http\Kernel as HttpKernel;

class Kernel extends HttpKernel
{
    /**
     * The application's global HTTP middleware stack.
     *
     * These middleware are run during every request to your application.
     *
     * @var array<int, class-string|string>
     */
    protected $middleware = [
        // \App\Http\Middleware\TrustHosts::class,
        \App\Http\Middleware\TrustProxies::class,
        \Fruitcake\Cors\HandleCors::class,
        \App\Http\Middleware\PreventRequestsDuringMaintenance::class,
        \Illuminate\Foundation\Http\Middleware\ValidatePostSize::class,
        \App\Http\Middleware\TrimStrings::class,
        \Illuminate\Foundation\Http\Middleware\ConvertEmptyStringsToNull::class,
        CheckAge::class
    ];

    /**
     * The application's route middleware groups.
     *
     * @var array<string, array<int, class-string|string>>
     */
    protected $middlewareGroups = [
        'web' => [
            \App\Http\Middleware\EncryptCookies::class,
            \Illuminate\Cookie\Middleware\AddQueuedCookiesToResponse::class,
            \Illuminate\Session\Middleware\StartSession::class,
            // \Illuminate\Session\Middleware\AuthenticateSession::class,
            \Illuminate\View\Middleware\ShareErrorsFromSession::class,
            \App\Http\Middleware\VerifyCsrfToken::class,
            \Illuminate\Routing\Middleware\SubstituteBindings::class,
        ],

        'api' => [
            // \Laravel\Sanctum\Http\Middleware\EnsureFrontendRequestsAreStateful::class,
            'throttle:api',
            \Illuminate\Routing\Middleware\SubstituteBindings::class,
        ],
    ];

    /**
     * The application's route middleware.
     *
     * These middleware may be assigned to groups or used individually.
     *
     * @var array<string, class-string|string>
     */
    protected $routeMiddleware = [
        'auth' => \App\Http\Middleware\Authenticate::class,
        'auth.basic' => \Illuminate\Auth\Middleware\AuthenticateWithBasicAuth::class,
        'cache.headers' => \Illuminate\Http\Middleware\SetCacheHeaders::class,
        'can' => \Illuminate\Auth\Middleware\Authorize::class,
        'guest' => \App\Http\Middleware\RedirectIfAuthenticated::class,
        'password.confirm' => \Illuminate\Auth\Middleware\RequirePassword::class,
        'signed' => \Illuminate\Routing\Middleware\ValidateSignature::class,
        'throttle' => \Illuminate\Routing\Middleware\ThrottleRequests::class,
        'verified' => \Illuminate\Auth\Middleware\EnsureEmailIsVerified::class,
        'checkAge' => CheckAge::class
    ];
} 

2.定义一个路由

 Route::get('/', function () {
    return view('welcome');
});

3.启动服务php artisan serve并访问地址 127.0.0.1:8000

如图所示，中间件已生效。
中间件作用于某些特定的路径地址
1. 和上面一样，打开kernel.php 文件（D:\test\yxjc123\app\Http\Kernel.php）。在routeMiddleware 数组中添加 CheckAge类。
2. 打开刚才创建的中间件文件CheckAge.php

<?php

namespace App\Http\Middleware;

use Closure;
use Illuminate\Http\Request;

class CheckAge
{
    /**
     * Handle an incoming request.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  \Closure(\Illuminate\Http\Request): (\Illuminate\Http\Response|\Illuminate\Http\RedirectResponse)  $next
     * @return \Illuminate\Http\Response|\Illuminate\Http\RedirectResponse
     */
    public function handle(Request $request, Closure $next)
    {
        echo "checkAge";//todo 判断

        return $next($request);
    }
}

3. 在路由文件web.php文件中增加中间件代码。

Route::get('/', function () {
    return view('welcome');
})-> middleware('checkAge');
Route::Get('/test',function()
{
    return "test";
});

最后在浏览器地址 栏中输入
http://127.0.0.1:8000/test 
http://127.0.0.1:8000/
返回的结果不一样，因为中间件只作用了路径/没有作用于/test。

中间件参数校验

中间件也可以进行参数校验。 让我们通过下面的例子来理解。

Route::Get('/{age}',function($age)  
{  
  return view('welcome');  
})-> middleware('checkAge'); 

打开刚才创建的中间件文件CheckAge.php

 <?php

namespace App\Http\Middleware;

use Closure;
use Illuminate\Http\Request;

class CheckAge
{
    /**
     * Handle an incoming request.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  \Closure(\Illuminate\Http\Request): (\Illuminate\Http\Response|\Illuminate\Http\RedirectResponse)  $next
     * @return \Illuminate\Http\Response|\Illuminate\Http\RedirectResponse
     */
    public function handle(Request $request, Closure $next)
    {
        //echo "checkAge";
        if($request->age>10)
        {
            return response()->json(['error' => "check age error ！"], 501);
        }

        return $next($request);
    }
}