Web Frameworks

A web framework helps you build backend applications faster by giving you common building blocks and a consistent structure.

Even though frameworks look different (Express, Django, Spring, Laravel, ASP.NET), they all solve the same problems.

What Web Frameworks Have in Common

1) Routing

Routing maps a request to a handler based on:

• HTTP method (GET/POST/PUT/PATCH/DELETE)
• URL path (like /users/42)

Example idea (framework-agnostic):

• GET /users → list users
• GET /users/:id → get one user

2) Request + Response

Frameworks provide an abstraction for:

• the incoming request (headers, params, body)
• the outgoing response (status code, JSON/HTML)

You always do the same flow:

1. Read input from the request
2. Execute business logic
3. Return a response

3) Middleware / Filters / Interceptors

Most frameworks have a concept of “code that runs before/after your routes”.

Typical uses:

• logging
• authentication
• rate limiting
• adding shared data to the request

Naming differs:

• Express: middleware
• Spring: filters, interceptors
• ASP.NET: middleware
• NestJS: guards, interceptors

4) Controllers / Handlers

A handler (sometimes called a controller action) is the function that runs when a route matches.

Handlers are usually kept small and call services/helpers to do the real work.

5) Error Handling

Frameworks provide a standard way to:

• handle “not found” routes
• return consistent server errors
• centralize error formatting

6) Parsing the Body

Almost every backend needs to read request bodies:

• JSON (application/json)
• form data (application/x-www-form-urlencoded)
• file uploads (multipart/form-data)

Frameworks either include body parsing or plug it in.

7) Serving Static Files

Many frameworks can serve static files (images, CSS, downloads) or integrate with a reverse proxy.

8) Configuration + Environments

Frameworks support:

• configuration files
• environment variables
• dev vs production behavior

9) Database Integration (Common Pattern)

Frameworks don’t have to include databases, but most projects add:

• an ORM/query builder
• migrations
• connection pooling

One Concept, Many Frameworks (Mapping)

This is the same idea written in different frameworks:

Concept	Express (Node)	Django (Python)	Spring (Java)	Laravel (PHP)
Route	app.get('/users', ...)	path('users/', ...)	@GetMapping("/users")	Route::get('/users', ...)
Handler	function	view function/class	controller method	controller method
Middleware	app.use(...)	middleware classes	filters/interceptors	middleware
JSON response	res.json(...)	JsonResponse(...)	return object	return response()->json(...)

You don’t need to memorize syntax—focus on the concept and then learn the framework’s way of writing it.

Choosing a Web Framework

• Minimal frameworks (Express): more freedom, less structure
• Opinionated frameworks (NestJS, Django, Spring): more structure, more built-in patterns

Where Web Frameworks Are Used

• Backend APIs (REST, GraphQL)
• Server-rendered apps (HTML pages)
• Internal tools and admin panels

Industry examples:

• Netflix: large Node.js usage for web services
• Google: heavy Java/Spring usage across many systems
• Shopify: Ruby on Rails for large parts of its product

Next

• Learn a concrete framework: Express.js
• For API design concepts: API Styles