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| 1 // Copyright (c) 2014, the Dart project authors. Please see the AUTHORS file | |
| 2 // for details. All rights reserved. Use of this source code is governed by a | |
| 3 // BSD-style license that can be found in the LICENSE file. | |
| 4 | |
| 5 library shelf.middleware; | |
| 6 | |
| 7 import 'request.dart'; | |
| 8 import 'response.dart'; | |
| 9 import 'handler.dart'; | |
| 10 import 'hijack_exception.dart'; | |
| 11 import 'util.dart'; | |
| 12 | |
| 13 /// A function which creates a new [Handler] by wrapping a [Handler]. | |
| 14 /// | |
| 15 /// You can extend the functions of a [Handler] by wrapping it in | |
| 16 /// [Middleware] that can intercept and process a request before it it sent | |
| 17 /// to a handler, a response after it is sent by a handler, or both. | |
| 18 /// | |
| 19 /// Because [Middleware] consumes a [Handler] and returns a new | |
| 20 /// [Handler], multiple [Middleware] instances can be composed | |
| 21 /// together to offer rich functionality. | |
| 22 /// | |
| 23 /// Common uses for middleware include caching, logging, and authentication. | |
| 24 /// | |
| 25 /// Middleware that captures exceptions should be sure to pass | |
| 26 /// [HijackException]s on without modification. | |
| 27 /// | |
| 28 /// A simple [Middleware] can be created using [createMiddleware]. | |
| 29 typedef Handler Middleware(Handler innerHandler); | |
| 30 | |
| 31 /// Creates a [Middleware] using the provided functions. | |
| 32 /// | |
| 33 /// If provided, [requestHandler] receives a [Request]. It can respond to | |
| 34 /// the request by returning a [Response] or [Future<Response>]. | |
| 35 /// [requestHandler] can also return `null` for some or all requests in which | |
| 36 /// case the request is sent to the inner [Handler]. | |
| 37 /// | |
| 38 /// If provided, [responseHandler] is called with the [Response] generated | |
| 39 /// by the inner [Handler]. Responses generated by [requestHandler] are not | |
| 40 /// sent to [responseHandler]. | |
| 41 /// | |
| 42 /// [responseHandler] should return either a [Response] or | |
| 43 /// [Future<Response>]. It may return the response parameter it receives or | |
| 44 /// create a new response object. | |
| 45 /// | |
| 46 /// If provided, [errorHandler] receives errors thrown by the inner handler. It | |
| 47 /// does not receive errors thrown by [requestHandler] or [responseHandler], nor | |
| 48 /// does it receive [HijackException]s. It can either return a new response or | |
| 49 /// throw an error. | |
| 50 Middleware createMiddleware({requestHandler(Request request), | |
| 51 responseHandler(Response response), | |
| 52 errorHandler(error, StackTrace stackTrace)}) { | |
| 53 if (requestHandler == null) requestHandler = (request) => null; | |
| 54 | |
| 55 if (responseHandler == null) responseHandler = (response) => response; | |
| 56 | |
| 57 var onError = null; | |
| 58 if (errorHandler != null) { | |
| 59 onError = (error, stackTrace) { | |
| 60 if (error is HijackException) throw error; | |
| 61 return errorHandler(error, stackTrace); | |
| 62 }; | |
| 63 } | |
| 64 | |
| 65 return (Handler innerHandler) { | |
| 66 return (request) { | |
| 67 return syncFuture(() => requestHandler(request)).then((response) { | |
| 68 if (response != null) return response; | |
| 69 | |
| 70 return syncFuture(() => innerHandler(request)) | |
| 71 .then((response) => responseHandler(response), onError: onError); | |
| 72 }); | |
| 73 }; | |
| 74 }; | |
| 75 } | |
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Chromium Code Reviews
Issue 814113004:
Pull args, intl, logging, shelf, and source_maps out of the SDK. (Closed)
Base URL: https://dart.googlecode.com/svn/branches/bleeding_edge/dart