Next.js API Routes & Middleware

Next.js allows you to build API endpoints as part of your application using Route Handlers in the App Router.

Route Handlers

// app/api/users/route.ts
import { NextRequest, NextResponse } from 'next/server';
import { db } from '@/lib/database';

// GET /api/users
export async function GET(request: NextRequest) {
  const searchParams = request.nextUrl.searchParams;
  const query = searchParams.get('query');
  
  const users = await db.user.findMany({
    where: query ? { name: { contains: query } } : undefined
  });
  
  return NextResponse.json(users);
}

// POST /api/users
export async function POST(request: NextRequest) {
  const body = await request.json();
  
  const user = await db.user.create({
    data: body
  });
  
  return NextResponse.json(user, { status: 201 });
}

// Dynamic route: app/api/users/[id]/route.ts
export async function GET(
  request: NextRequest,
  { params }: { params: { id: string } }
) {
  const user = await db.user.findUnique({
    where: { id: params.id }
  });
  
  if (!user) {
    return NextResponse.json(
      { error: 'User not found' },
      { status: 404 }
    );
  }
  
  return NextResponse.json(user);
}

export async function PATCH(
  request: NextRequest,
  { params }: { params: { id: string } }
) {
  const body = await request.json();
  
  const user = await db.user.update({
    where: { id: params.id },
    data: body
  });
  
  return NextResponse.json(user);
}

export async function DELETE(
  request: NextRequest,
  { params }: { params: { id: string } }
) {
  await db.user.delete({
    where: { id: params.id }
  });
  
  return NextResponse.json({ success: true });
}

Middleware

// middleware.ts (root of project)
import { NextResponse } from 'next/server';
import type { NextRequest } from 'next/server';

export function middleware(request: NextRequest) {
  // Check authentication
  const token = request.cookies.get('token')?.value;
  
  if (!token && request.nextUrl.pathname.startsWith('/dashboard')) {
    return NextResponse.redirect(new URL('/login', request.url));
  }
  
  // Add custom headers
  const response = NextResponse.next();
  response.headers.set('x-custom-header', 'value');
  
  return response;
}

// Configure which paths middleware runs on
export const config = {
  matcher: ['/dashboard/:path*', '/api/:path*']
};