shelf

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Shelf interop with Angel. This package lets you run package:shelf handlers via a custom adapter. It also includes a plug-in that configures Angel to natively run shelf response handlers.

Use the code in this repo to embed existing shelf apps into your Angel applications. This way, you can migrate legacy applications without having to rewrite your business logic.

This will make it easy to layer your API over a production application, rather than having to port code.

Usage

embedShelf

This is a compliant shelf adapter that acts as an Angel request handler. You can use it as a middleware, or attach it to individual routes.

import 'dart:io';
import 'package:angel_framework/angel_framework.dart';
import 'package:angel_shelf/angel_shelf.dart';
import 'package:shelf/shelf.dart' as shelf;
import 'api/api.dart';

main() async {
  final app = new Angel();
  
  // Angel routes on top
  await app.configure(new ApiController());
  
  // Re-route all other traffic to an
  // existing application.
  app.after.add(embedShelf(
    new shelf.Pipeline()
      .addMiddleware(shelf.logRequests())
      .addHandler(_echoRequest)
  ));
  
  // Only on a specific route
  app.get('/shelf', handler);
  
  await app.startServer(InternetAddress.LOOPBACK_IP_V4, 3000);
}

Communicating with Angel with embedShelf

You can communicate with Angel:

handleRequest(shelf.Request request) {
  // Access original Angel request...
  var req = request.context['angel_shelf.request'] as RequestContext;
  
  // ... And then interact with it.
  req.inject('from_shelf', new Foo());
  
  // `req.properties` are also available.
  var props = request.context['angel_shelf.properties'] as Map;
  
}

supportShelf

This plug-in takes advantage of Angel's middleware system and dependency injection to patch a server to run shelf request handlers as though they were Angel request handlers. Hooray for integration!

You'll want to run this before adding any other response finalizers that depend on the response content being effectively final, i.e. GZIP compression.

NOTE: Do not inject a shelf.Request into your request under the name req. If you do, Angel will automatically inject a RequestContext instead.

configureServer(Angel app) async {
  // Return a shelf Response
  app.get('/shelf', (shelf.Request request) => new shelf.Response.ok('Yay!'));
  
  // Return an arbitrary value.
  //
  // This will be serialized by Angel as per usual.
  app.get('/json', (shelf.Request request) => {'foo': 'bar'});
  
  // You can still throw Angel exceptions.
  //
  // Don't be fooled: just because this is a shelf handler, doesn't mean
  // it's not an Angel response handler too. ;)
  app.get('/error', (shelf.Request request) {
    throw new AngelHttpException.forbidden();
  });
  
  // Make it all happen!
  await app.configure(supportShelf());
}

Communicating with Angel with supportShelf

The following keys will be present in the shelf request's context:

  • angel_shelf.request - Original RequestContext
  • angel_shelf.response - Original ResponseContext
  • angel_shelf.properties - Original RequestContext's properties

If the original RequestContext contains a Map named shelf_context in its properties, then it will be merged into the shelf request's context.

If the handler returns a shelf.Response, then it will be present in ResponseContext.properties as shelf_response.

Libraries

angel_shelf