Next.js 15 Fullstack Web Apps · Ders

Ara Katman Yazılımı ve Erişim Denetimi

Yetkilendirme ve yönlendirme için Next.js Ara Katman Yazılımını kullanarak yolları ve API uç noktalarını koruyun.

Ara Katman Yazılımı ve Erişim Denetimi, CoddyKit'te ücretsiz bir Next.js 15 Fullstack Web Apps dersidir. Bu, 4 dersinin 3. dersidir. Aşağıdan dersin tamamını ücretsiz okuyabilir, sonra tarayıcıda yerleşik kod editörü ve 7/24 yapay zeka koçu ile uygulamalı olarak pratik yapabilirsin. Bu, Next.js 15 Fullstack Web Apps öğrenme yolunun bir parçasıdır ve ilerlemeniz web ve CoddyKit uygulaması arasında senkronize olur. Next.js 15 Fullstack Web Apps kursu toplamda 4 dersten oluşur.

Bu dersin bazı bölümleri henüz çevrilmemiş olup İngilizce olarak gösterilmektedir.

Intercepting Requests with Middleware

Welcome to Lesson 3! In this lesson, we'll explore Next.js Middleware. Think of middleware as a gatekeeper for your application.

It allows you to run code before a request is completed, letting you inspect, modify, or even redirect requests based on certain conditions. This is super useful for access control!

Creating Your First Middleware

To create middleware, you simply add a middleware.ts (or .js) file at the root of your project, or inside the src directory.

This file must export a default function that takes a NextRequest object and returns a NextResponse. Let's create a basic one:

import { NextResponse } from 'next/server';
import type { NextRequest } from 'next/server';

export function middleware(request: NextRequest) {
  console.log('Middleware is running!');
  // Continue to the requested page
  return NextResponse.next();
}

Basic Redirection for Access Control

A common use case for middleware is to protect routes. For example, you might want to redirect users who aren't logged in away from a dashboard page.

Here, we'll simulate checking for an 'auth_token' cookie. If it's missing, we redirect the user to the homepage.

import { NextResponse } from 'next/server';
import type { NextRequest } from 'next/server';

export function middleware(request: NextRequest) {
  const isAuthenticated = request.cookies.has('auth_token');
  const { pathname } = request.nextUrl;

  // If not authenticated and trying to access /dashboard
  if (!isAuthenticated && pathname.startsWith('/dashboard')) {
    console.log('User not authenticated, redirecting...');
    return NextResponse.redirect(new URL('/', request.url));
  }

  return NextResponse.next();
}

Defining Middleware Scope with `matcher`

By default, middleware runs on every request. This isn't always efficient. You can specify which paths your middleware should run on using the config.matcher property.

The matcher is an array of strings that define path patterns. It's more powerful and recommended than conditional logic inside the middleware function for path filtering.

Using `matcher` for Specific Paths

Let's update our middleware to only run on paths that start with /dashboard or /profile. This makes our middleware more performant by not running on unnecessary routes.

/dashboard/:path* matches /dashboard and any sub-paths like /dashboard/settings.
/profile/:path* matches /profile and its sub-paths.

import { NextResponse } from 'next/server';
import type { NextRequest } from 'next/server';

export function middleware(request: NextRequest) {
  const isAuthenticated = request.cookies.has('auth_token');

  if (!isAuthenticated) {
    console.log('Not authenticated, redirecting to home.');
    return NextResponse.redirect(new URL('/', request.url));
  }

  return NextResponse.next();
}

export const config = {
  matcher: ['/dashboard/:path*', '/profile/:path*'],
};

Reading & Modifying Request Headers

Middleware can also read and modify request headers. This is useful for passing information down to your pages or API routes, or for adding security headers.

The NextRequest object provides methods to interact with headers, cookies, and the URL.

import { NextResponse } from 'next/server';
import type { NextRequest } from 'next/server';

export function middleware(request: NextRequest) {
  const requestHeaders = new Headers(request.headers);
  const userAgent = requestHeaders.get('user-agent');
  console.log('User-Agent:', userAgent);

  // Add a custom header
  requestHeaders.set('x-custom-header', 'Hello from Middleware');

  // Return a new response with modified headers
  return NextResponse.next({
    request: { headers: requestHeaders },
  });
}

Protecting API Routes with Middleware

Middleware applies to all routes in your application, including API routes (e.g., /api/users). This is a powerful feature for implementing API authentication and authorization.

You can check for API keys, JWTs, or session tokens in the request headers or cookies before allowing access to your API endpoints.

Authorization vs. Authentication

It's important to distinguish between Authentication (AuthN) and Authorization (AuthZ):

Authentication: Verifies who a user is (e.g., by checking their login credentials).
Authorization: Determines what an authenticated user is allowed to do (e.g., access admin pages, delete content).

Middleware can enforce both, by checking if a user is logged in (AuthN) and if they have the necessary roles/permissions (AuthZ) before granting access to a route.

Advanced Authorization Example

Let's combine concepts for a more advanced scenario: checking for an 'admin' role. We'll simulate reading a user role from a cookie and redirecting non-admin users from an /admin path.

This shows how middleware acts as a central point for access control logic.

import { NextResponse } from 'next/server';
import type { NextRequest } from 'next/server';

export function middleware(request: NextRequest) {
  const userRole = request.cookies.get('user_role')?.value;
  const { pathname } = request.nextUrl;

  // If trying to access /admin routes
  if (pathname.startsWith('/admin')) {
    // Check if user has 'admin' role
    if (userRole !== 'admin') {
      console.log('Access denied: User is not an admin, redirecting.');
      return NextResponse.redirect(new URL('/unauthorized', request.url));
    }
  }

  return NextResponse.next();
}

export const config = {
  matcher: ['/admin/:path*'],
};

Middleware Matching Challenge

Consider the following config.matcher. Which of these paths WILL be processed by the middleware?

export const config = {
  matcher: ['/dashboard/:path*', '/settings'],
};

Recap: Middleware for Control

You've learned how Next.js Middleware acts as a powerful interceptor for incoming requests.

It's defined in a middleware.ts file.
It can redirect users, modify requests/responses, and add headers.
The config.matcher is essential for defining which routes your middleware should protect.
It's crucial for implementing both authentication and authorization logic across your application, including API routes.

Middleware gives you fine-grained control over access and behavior!

Sıkça Sorulan Sorular

“Ara Katman Yazılımı ve Erişim Denetimi” dersi ücretsiz mi?

Evet — “Ara Katman Yazılımı ve Erişim Denetimi” dersin tüm metni burada web'de ücretsiz olarak okunabilir. Etkileşimli olarak pratik yapmak (yerleşik kod editörü ve 7/24 yapay zeka koçu) ve Next.js 15 Fullstack Web Apps kursunun geri kalanını açmak için CoddyKit PRO'ya yükselt. Next.js 15 Fullstack Web Apps kursu toplamda 4 dersten oluşur.

“Ara Katman Yazılımı ve Erişim Denetimi” dersinde ne öğreneceğim?

Yetkilendirme ve yönlendirme için Next.js Ara Katman Yazılımını kullanarak yolları ve API uç noktalarını koruyun. Next.js 15 Fullstack Web Apps ile uygulamalı kodu tarayıcıda doğrudan çalıştırarak pratik yaparsın ve 7/24 yapay zeka koçu dersi çalışırken sorularını yanıtlar.

Next.js 15 Fullstack Web Apps öğrenmeye başlamak için deneyim gerekli mi?

Önceden deneyim gerekmez. CoddyKit'te Next.js 15 Fullstack Web Apps, başlangıçtan ileri seviyeye kadar yapılandırıldığı için buradan başlayabilir veya başından başlayıp kendi hızında ilerleme yapabilirsin. Bu, 4 dersinin 3. dersidir.

“Ara Katman Yazılımı ve Erişim Denetimi” dersi ne kadar sürer?

Çoğu CoddyKit dersi yaklaşık 5–10 dakika sürer. Her biri kısa ve etkileşimli olduğu için sabit ilerleme yaparsın ve web ile uygulama arasında tam olarak bıraktığın yerden devam edebilirsin.

Bu Next.js 15 Fullstack Web Apps dersinde kod yazıp çalıştırabilir miyim?

Evet. Her Next.js 15 Fullstack Web Apps dersi yerleşik bir kod editörü içerir, bu sayede tarayıcıda gerçek kod yazıp çalıştırabilir ve anlık yapay zeka geri bildirimi alırsın — yerel kurulum gerekli değildir.

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