Summary - Shelf

Combine Handler, Middleware and Router to write an API.

Summary - Shelf

This group covered the shelf HTTP framework: handler (Request → Response), middleware (handler wrapping), shelf_router (URL routing), JSON responses.

Core: a handler is a function; it is wrapped by middleware; a Router maps URLs to handlers; JSON needs jsonEncode + a content-type header.

It connects to HttpServer via shelf_io; for testing, handlers can be called directly.

Exercise Summary: handler + JSON

Add import 'package:shelf/shelf.dart'; import 'dart:convert';. Define Response healthHandler(Request r) => Response.ok(jsonEncode({'status': 'ok'}), headers: {'content-type': 'application/json'});. Make main async; call the handler and add print(await resp.readAsString());.

Show example solution

import 'package:shelf/shelf.dart';
import 'dart:convert';

Response healthHandler(Request r) =>
    Response.ok(jsonEncode({'status': 'ok'}),
        headers: {'content-type': 'application/json'});

void main() async {
  var resp = healthHandler(Request('GET', Uri.parse('http://localhost/')));
  print(await resp.readAsString());
}

Test yourself

Which is required for JSON?
- Router
- content-type header
- Isolate
- Future.delayed
Show answer

content-type header — JSON requires the content-type: application/json header.
Match the concepts

Handler

Request → Response
Middleware

Handler wrapping
Router

URL → handler
jsonEncode

Map → String

200 response

return ____.ok('merhaba');

Show answer

return Response.ok('merhaba');

Next lesson: http package

We Are Enhancing Your Experience

Cookie Preferences

Strictly Necessary Cookies

Analytical Cookies