Index: pkg/shelf/lib/src/middleware.dart |
diff --git a/pkg/shelf/lib/src/middleware.dart b/pkg/shelf/lib/src/middleware.dart |
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+// Copyright (c) 2014, the Dart project authors. Please see the AUTHORS file |
+// for details. All rights reserved. Use of this source code is governed by a |
+// BSD-style license that can be found in the LICENSE file. |
+ |
+library shelf.middleware; |
+ |
+import 'request.dart'; |
+import 'response.dart'; |
+import 'handler.dart'; |
+import 'util.dart'; |
+ |
+/// A function which creates a new [Handler] by wrapping a [Handler]. |
+/// |
+/// You can extend the functions of a [Handler] by wrapping it in |
+/// [Middleware] that can intercept and process a request before it it sent |
+/// to a handler, a response after it is sent by a handler, or both. |
+/// |
+/// Because [Middleware] consumes a [Handler] and returns a new |
+/// [Handler], multiple [Middleware] instances can be composed |
+/// together to offer rich functionality. |
+/// |
+/// Common uses for middleware include caching, logging, and authentication. |
+/// |
+/// A simple [Middleware] can be created using [createMiddleware]. |
+typedef Handler Middleware(Handler innerHandler); |
+ |
+/// Creates a [Middleware] using the provided functions. |
+/// |
+/// If provided, [requestHandler] receives a [Request]. It can respond to |
+/// the request by returning a [Response] or [Future<Response>]. |
+/// [requestHandler] can also return `null` for some or all requests in which |
+/// case the request is sent to the inner [Handler]. |
+/// |
+/// If provided, [responseHandler] is called with the [Response] generated |
+/// by the inner [Handler]. Responses generated by [requestHandler] are not |
+/// sent to [responseHandler]. |
+/// |
+/// [responseHandler] should return either a [Response] or |
+/// [Future<Response>]. It may return the response parameter it receives or |
+/// create a new response object. |
+/// |
+/// If provided, [errorHandler] receives errors thrown by the inner handler. It |
+/// does not receive errors thrown by [requestHandler] or [responseHandler]. It |
+/// can either return a new response or throw an error. |
+Middleware createMiddleware({requestHandler(Request request), |
+ responseHandler(Response response), |
+ errorHandler(error, StackTrace stackTrace)}) { |
+ if (requestHandler == null) requestHandler = (request) => null; |
+ |
+ if (responseHandler == null) responseHandler = (response) => response; |
+ |
+ return (Handler innerHandler) { |
+ return (request) { |
+ return syncFuture(() => requestHandler(request)).then((response) { |
+ if (response != null) return response; |
+ |
+ return syncFuture(() => innerHandler(request)) |
+ .then((response) => responseHandler(response), |
+ onError: errorHandler); |
+ }); |
+ }; |
+ }; |
+} |