shelf
- Dart course
- Advanced
- Lesson 25/83
- 5 min
Learn HTTP servers with shelf.
The shelf package
shelf is a minimal HTTP server framework for Dart. It takes requests (Request), passes them to a user-defined handler, and returns a Response.
A handler is a function with signature Response Function(Request). shelf calls it; you produce a Response.
shelf itself is not a server; the shelf_io adapter connects it to an HttpServer. This separation makes testing easy and adapters portable.
Responding with Response.ok
Response.ok(body) creates a 200-status response. body can be a String, List<int> or Stream<List<int>>.
Example handler: Response helloHandler(Request req) => Response.ok('merhaba');. This handler returns 200 with body 'merhaba' on every request.
To test the handler, call it directly without starting shelf_io: var r = helloHandler(...); print(r.statusCode);.
Practice Define and call a handler
Add import 'package:shelf/shelf.dart';. Define Response helloHandler(Request req) => Response.ok('merhaba');. In main add var r = helloHandler(Request('GET', Uri.parse('http://localhost/'))); and print(r.statusCode);.
Starter code
void main() {
// add shelf import; define helloHandler (outside main)
// call the handler and print the status code
}Sample solution
import 'package:shelf/shelf.dart';
Response helloHandler(Request req) => Response.ok('merhaba');
void main() {
var r = helloHandler(Request('GET', Uri.parse('http://localhost/')));
print(r.statusCode);
}Expected output
200
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 What is shelf's core abstraction?
- Handler (Request → Response) Correct answer
- Stream
- Widget
- Future
Explanation: a handler takes a Request and returns a Response.
2 Handler signature
Response helloHandler(____ req) => Response.ok('merhaba');Response helloHandler(Request req) => Response.ok('merhaba');Explanation: a handler takes a Request parameter.
3 Match the shelf concepts
| Term | Meaning |
|---|---|
Request |
Incoming request |
Response |
Outgoing response |
Handler |
Request → Response |
shelf_io |
HttpServer adapter |