How do I register multiple handlers for a HttpServer, in Dart? - dart

Question

(I'm using the new lib v2 version of dart:io.)
I'd like to register multiple handlers for an HttpServer, specifically a WebSocketTransformer and other arbitrary handlers. Something like this:
// pseudo-code
var server = HttpServer;
server.register('/foo', someHandlerFunction); // 1
server.register('/bar', someOtherHandlerFunction); // 2
server.register('/ws', webSocketHandler); // 3
If #1 matches, then #2 isn't tested, and so on. So, it's greedy.
I've seen samples with just one handler. How do I register many handlers? Thanks in advance!

Answer 1

New answer: Use the route package: http://pub.dartlang.org/packages/route
Here's your example using route's serve() method:
HttpServer.bind('127.0.0.1', 8889).then((server) {
var router = new Router(server)
..serve('/ws').transform(new WebSocketTransformer()).listen(handleWebSocket)
..serve('/foo').listen((req) {
req.response..addString('foo')..close();
});
});
Router automatically catches unhandled requests and sends a 404, though soon you'll be able to override that with a defaultStream you can listen to.
Router also supports filters, useful for logging, auth, compression, etc.:
HttpServer.bind('127.0.0.1', 8889).then((server) {
var router = new Router(server)
..filter(new RegExp(r'/.*'), (req) {
//log all requests
_logger.info("request: $req");
return new Future.immediate(true); // keep processing request
})
..filter(new Regexp(r'/secure/.*'), (req) {
// check authentication asynchronously
return getUserFromRequest(req).then((user) {
if (user == null) {
sendRedirect('/login'); // sendRedirect coming soon
return false; // stop processing request
} else {
return true; // keep processing
}
});
})
..serve(/* ... */ );
});

Answer 2

Here's how the API docs recommend to register a WebSocket handler:
server
.where((request) => request.uri.path == "/ws")
.transform(new WebSocketTransformer()).listen((webSocket) => ...);
However, the server is a single-subscription stream. Once a listen is attached, you can't attach other listeners.
What I really want is for something to look at an event, decide if it can handle it, and if so then route it to another stream. Otherwise, pass it along. This way, the event (in this case an HttpRequest object) is passed along a chain until it's handled.
I built a TakeAndRoute class that extends StreamEventTransformer. The TakeAndRoute uses a function to determine if it should grab the event and route it to another stream, or simply forward it along.
Here's what I came up with:
import 'dart:io';
import 'dart:async';
handleWebSocket(WebSocket webSocket) {
webSocket.listen((event) {
if (event is MessageEvent) {
/* Handle message. */
} else if (event is CloseEvent) {
/* Handle closed. */
}
});
}
typedef bool ShouldTake(e);
typedef void RouteTo(Stream stream);
typedef void HandleEvent(e);
class TakeAndRoute<S, T> extends StreamEventTransformer<S, T> {
ShouldTake shouldTake;
RouteTo routeTo;
StreamController controller = new StreamController();
HandleEvent handler;
TakeAndRoute(this.shouldTake, {this.routeTo, this.handler}) {
if (routeTo != null) routeTo(controller.stream);
}
handleData(event, StreamSink sink) {
print("handling");
if (shouldTake(event)) {
if (routeTo != null) {
controller.add(event);
}
if (handler != null) {
handler(event);
}
} else {
sink.add(event);
}
}
}
main() {
HttpServer.bind('127.0.0.1', 8888)
.then((HttpServer server) {
server
.transform(new TakeAndRoute<HttpRequest, HttpRequest>(
(req) => req.uri.path == '/ws',
routeTo: (stream) => stream.transform(new WebSocketTransformer()).listen(handleWebSocket)))
.transform(new TakeAndRoute<HttpRequest, HttpRequest>(
(req) => req.uri.path == '/foo',
handler: (req) {
print('got foo');
req.response.addString("foo");
req.response.close();
}))
.listen((req) {
print("got 404 for ${req.uri}");
req.response.statusCode = 404;
req.response.close();
});
});
}
Admittedly, this might be overkill.

Answer 3

Here is a more manual, but shorter way to do it:
HttpServer.bind('127.0.0.1', 8889)
.then((HttpServer server) {
var sc = new StreamController();
sc.stream.transform(new WebSocketTransformer()).listen(handleWebSocket);
server.listen((HttpRequest request) {
print("new connection from ${request.uri.scheme} ${request.uri}");
// See https://code.google.com/p/dart/issues/detail?id=8825
//if (request.uri.scheme == 'ws') {
if (request.uri.path == '/ws') {
sc.add(request);
} else if (request.uri.path == '/foo') {
request.response.addString('foo');
request.response.close();
} else {
print("got 404 for ${request.uri}");
request.response.statusCode = 404;
request.response.close();
}
});
});
Notice how I had to create a StreamController so I could pump events to WebSocketTransformer