In Laravel, duplicate code can be reduced through global middleware and middleware groups. Global middleware is suitable for all requests, such as setting time zones and loading language packs. The registration method is to add class names to the $middleware array of app/Http/Kernel.php, but time-consuming operations should be avoided; middleware groups are used to apply multiple middleware to a set of routes on demand, such as web and API groups. They can be customized and applied to routes, such as authentication and permission judgment middleware to form an admin group, and applied through Route::middleware('admin'); global middleware is selected for system-level operations, and middleware groups are used for business division, thereby improving project structure clarity and maintainability.

In Laravel, if you want some middleware to take effect on all routes or groups of routes instead of adding them to each route one by one, you can use a global middleware or middleware group. This method can reduce duplicate code and improve maintainability.

Global Middleware: Applicable to all requests

The global middleware will be executed in every request . Common uses include loading language packs at startup, setting default time zones, etc.

To register a global middleware:

1. Open app/Http/Kernel.php
2. Add your middleware class name in the $middleware array

For example:

 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,
    \App\Http\Middleware\LoadLanguage::class, // New global middleware];

Note: Global middleware will affect all requests, so don't put too much time-consuming operations in it, such as database query. Unless you do need it to work on all requests, it is recommended to use middleware groups to be more flexible.

Middleware group: applied on demand to common routing collections

Middleware groups are suitable for middleware combinations that you want to apply to multiple routes together. The most common examples are web and api groups.

To create or modify a middleware group:

1. Open app/Http/Kernel.php
2. Find $middlewareGroups array
3. Add or edit a list of middleware in a group

For example, if you want to add permission verification middleware to the background management page:

 'admin' => [
    \App\Http\Middleware\Authenticate::class,
    \App\Http\Middleware\CheckAdminRole::class,
    \Illuminate\Routing\Middleware\SubstituteBindings::class,
],

Then, when defining the route, use it like this:

 Route::middleware('admin')->prefix('admin')->group(function () {
    Route::get('/dashboard', [AdminController::class, 'dashboard']);
    Route::resource('users', UserController::class);
});

The advantage of this is that it has clear structure and is convenient for unified management. At the same time, it can also avoid writing a bunch of middleware on each route, reducing errors and maintenance costs.

How to choose a global or middleware group?

• Use global middleware : suitable for system-level operations, such as basic security restrictions, logging, initialization configuration, etc.
• Middleware group : suitable for business scenario division, such as web foreground, API interface, backend management, etc.

To give a practical example:

• You have a mall project, and the front-end user access requires session support, and the back-end administrator also needs additional authentication.
• Then you can place \App\Http\Middleware\EncryptCookies::class , \Illuminate\Session\Middleware\StartSession::class , etc. in web group.
• The background interface uses a custom admin group, which contains middleware for authentication permission judgment.

Basically that's it. Rational use of global and middleware groups can make your Laravel project structure clearer and easier to expand and maintain.

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