Għal xiex jintuża middleware ta' Next.js?

Question

Accepted Answer

**Middleware** huwa kodiċi li **jimxu qabel ma tlesti t-talba** — fuq Edge, qabel ma ġie rRendrat il-paġna jew route handler. Jippermettilak tainspetta u tikteb ieħor/tirdirizza t-talibiet, tistabbilixxi headers, jew tivverifika l-aut għal ħafna roti f'post wieħed.

## Defining middleware

```ts
// middleware.ts (at the project root)
import { NextRequest, NextResponse } from "next/server";

export function middleware(req: NextRequest) {
  const token = req.cookies.get("session")?.value;

// protect /dashboard — redirect unauthenticated users to login
  if (req.nextUrl.pathname.startsWith("/dashboard") && !token) {
    return NextResponse.redirect(new URL("/login", req.url));
  }
  return NextResponse.next(); // allow the request to proceed
}

// only run on these paths (performance — don't run on every asset)
export const config = { matcher: ["/dashboard/:path*", "/account/:path*"] };
```

## What middleware can do

```ts
NextResponse.redirect(url);          // send the user elsewhere (auth gates)
NextResponse.rewrite(url);           // serve different content, URL unchanged (A/B, i18n)
NextResponse.next();                  // continue, optionally with modified headers
// req.geo / req.cookies / req.headers — inspect location, auth, etc.
```

Użi komuni: **gating ta' awtorijazzjoni**, **ridjirezzjonamenti** (ibbazati fuq locale/geo, www→apex), **ittestjar A/B** permezz ta' rewrite, istabbiliment ta' **security headers**, u bot/feature flags.

## Key constraints

```text
⚠️ Runs on the EDGE runtime → no Node.js APIs (no fs, limited libraries)
⚠️ Must be FAST — it runs before every matched request; heavy work adds latency
⚠️ Can't access the database directly for complex auth — do lightweight checks
   (e.g. verify a JWT/cookie exists); do full auth in the page/handler
```

Il-konfigurazzjoni ta' `matcher` hija importanti: iddah il-middleware biss għar-roti li għandhom bżonn tiegħu, sabiex ma jdoqqox fuq l-assi statiċi u tibillan kollox.

## Għal xiex dan importanti

Middleware huwa l-punt ta' stotilament singolu għal-loġika ta' talba cross-cutting — ridjirezzjonamenti ta' awtorijazzjoni, routing ta' locale, rewrites, u headers — applikati fuq ħafna roti mingħajr ma jirrepeti l-kodiċi f'kull paġna.

Il-għarif tal-limitazzjonijiet tiegħu fuq Edge (mabist, l-ebda APIs ta' Node, ċekks ħfief biss) u l-ambitu ta' `matcher` huwa dak li jippermettilak tużah kif due għal concerns ta' gatekeeping u routing.