diff --git a/demo/index.js b/demo/index.js
index 352f6d8..09a2ce8 100755
--- a/demo/index.js
+++ b/demo/index.js
@@ -19,6 +19,19 @@ mockServer({
 		'Global-Custom-Header': 'Global-Custom-Header',
 	},
 	customDTOToClassTemplate: __dirname + '/templates/dto_es6flow.ejs',
+	middleware: {
+		'/rest/products/#{productCode}/GET'(serverOptions, requestOptions) {
+			var productCode = requestOptions.req.params[0].split('/')[3];
+
+			if (productCode === '1234') {
+				requestOptions.res.statusCode = 201;
+				requestOptions.res.end('product 1234');
+				return null;
+			}
+
+			return 'success';
+		}
+	},
 	swaggerImport: {
 		protocol: 'http',
 		authUser: undefined,
diff --git a/doc/readme-middleware.md b/doc/readme-middleware.md
new file mode 100644
index 0000000..28e19f0
--- /dev/null
+++ b/doc/readme-middleware.md
@@ -0,0 +1,20 @@
+# Middleware
+
+For validation and self controlled responses you can select middleware as response.
+The middleware function will be called, in case of "middleware" is selected. It's response can be a string which will continue with the given string as selected response. If you return null or undefined you have to implement the response by yourself.
+
+[example](/demo/index.js#L22)
+
+## Parameter[0] serverOptions
+
+See [node-mock-server options](/doc/readme-options.md)
+
+## Parameter[1] responseOptions
+
+| attribute     | type          | description  |
+| ------------- | ------------- | ----- |
+| req           | Object        | The (request object)[http://expressjs.com/en/api.html#req]. |
+| res           | Object        | The (response object)[http://expressjs.com/en/api.html#res]. |
+| method        | string        | Contains a string corresponding to the HTTP method of the request: GET, POST, PUT, and so on. |
+| dir           | string        | The directory of selected response |
+| preferences   | Object        | The preferences object |
diff --git a/doc/readme-options.md b/doc/readme-options.md
index 80a2534..509830b 100644
--- a/doc/readme-options.md
+++ b/doc/readme-options.md
@@ -97,6 +97,12 @@ Default value: `origin, x-requested-with, content-type`
 
 A string that define the header "Access-Control-Allow-Headers".
 
+#### options.middleware
+Type: `Object`
+Optional
+
+A object including the middleware functions.
+Read [middleware.md](/doc/readme-middleware.md) for details.
 
 #### options.swaggerImport
 Type: `Object`
diff --git a/lib/UserInterface.js b/lib/UserInterface.js
index 63ee966..4ba71c0 100755
--- a/lib/UserInterface.js
+++ b/lib/UserInterface.js
@@ -396,6 +396,9 @@ UserInterface.prototype = extend(UserInterface.prototype, {
 			}
 
 			var availableMockResponses = this.readDir(mockPath, ['response.txt', '.DS_Store']);
+			availableMockResponses.push({
+				file: 'middleware',
+			});
 			var availableMockResponsesOut = [];
 			var selected;
 			try {
diff --git a/lib/controller/MockController.js b/lib/controller/MockController.js
index eaa5a15..0d45f98 100644
--- a/lib/controller/MockController.js
+++ b/lib/controller/MockController.js
@@ -37,22 +37,34 @@ MockController.prototype = extend(MockController.prototype, {
 		appController.app.all('/*', this._handleMockRequest.bind(this));
 	},
 
+	/**
+	 * @method _acceptMiddleware
+	 * @param {Object} serverOptions
+	 * @param {Object} responseOptions
+	 * @private
+	 */
+	_acceptMiddleware: function (serverOptions, responseOptions) {
+		var endPointId = responseOptions.dir.replace(serverOptions.dirName, '').replace(/\/$/, '');
+		var middleware = serverOptions.middleware;
+
+		if (!endPointId || !middleware || typeof middleware[endPointId] !== 'function') {
+			responseOptions.res.statusCode = 500;
+			responseOptions.res.end('Error: middleware for ' + endPointId + '" don\'t exist!');
+			return false;
+		}
+
+		return middleware[endPointId](serverOptions, responseOptions);
+	},
+
 	/**
 	 * @method _handleMockRequest
-	 * @param {object} req
-	 * @param {object} res
+	 * @param {Object} req
+	 * @param {Object} res
 	 * @private
 	 */
 	_handleMockRequest: function (req, res) {
 
 		var path = req.originalUrl.replace(this.options.urlPath, this.options.restPath);
-		var method = req.method;
-		var dir = this._findFolder(path, this.options) + '/' + method + '/';
-		var expectedResponse = this._getExpectedResponse(req, dir);
-		var preferences = this.getPreferences(this.options);
-		var timeout = 0;
-		var responseFilePath;
-		var responseHeadersFilePath;
 		var responseHeaders;
 		var headers = this.options.headers || {};
 		var options;
@@ -62,55 +74,42 @@ MockController.prototype = extend(MockController.prototype, {
 			return true;
 		}
 
-		if (preferences && preferences.responseDelay) {
-			timeout = parseInt(preferences.responseDelay, 10);
-		}
+		options = this.getResponseOptions(req, res);
 
-		responseFilePath = dir + 'mock/' + expectedResponse + '.json';
-		responseHeadersFilePath = dir + 'mock/' + expectedResponse + '.headers.json';
+		if (!options) {
+			return;
+		}
 
 		// Fallback to success.json
-		if (!this.existFile(responseFilePath)) {
-			expectedResponse = 'success';
-			responseFilePath = dir + 'mock/success.json';
-			this.writeFile(dir + 'mock/response.txt', 'success');
+		if (!this.existFile(options.responseFilePath)) {
+			options.expectedResponse = 'success';
+			options.responseFilePath = options.dir + 'mock/success.json';
+			this.writeFile(options.dir + 'mock/response.txt', 'success');
 		}
 
 		// Add response headers
-		if (this.existFile(responseHeadersFilePath)) {
-			responseHeaders = JSON.parse(this.readFile(responseHeadersFilePath)) || {};
+		if (this.existFile(options.responseHeadersFilePath)) {
+			responseHeaders = JSON.parse(this.readFile(options.responseHeadersFilePath)) || {};
 		}
 
-		options = {
-			req: req,
-			res: res,
-			path: path,
-			method: method,
-			dir: dir,
-			expectedResponse: expectedResponse,
-			preferences: preferences,
-			timeout: timeout,
-			responseFilePath: responseFilePath,
-		};
-
 		this._writeDefaultHeader(res, extend(headers, responseHeaders));
 
 		setTimeout(function () {
 			if (!this._hasValidDynamicPathParam(options)) {
 				this._sendErrorEmptyPath(options);
-			} else if (expectedResponse.search('error') >= 0) {
+			} else if (options.expectedResponse.search('error') >= 0) {
 				this._sendError(options);
-			} else if (method === 'HEAD') {
+			} else if (options.method === 'HEAD') {
 				this._sendHead(options);
 			} else {
 				this._sendSuccess(options);
 			}
-		}.bind(this), timeout);
+		}.bind(this), options.timeout);
 	},
 
 	/**
 	 * @method _sendSuccess
-	 * @param {object} options
+	 * @param {Object} options
 	 * @returns {void}
 	 * @private
 	 */
@@ -146,9 +145,62 @@ MockController.prototype = extend(MockController.prototype, {
 
 	},
 
+	/**
+	 * @method getResponseOptions
+	 * @param {Object} req
+	 * @param {Object} res
+	 * @public
+	 */
+	getResponseOptions: function (req, res) {
+
+		var path = req.originalUrl.replace(this.options.urlPath, this.options.restPath);
+		var method = req.method;
+		var dir = this._findFolder(path, this.options) + '/' + method + '/';
+		var expectedResponse = this._getExpectedResponse(req, dir);
+		var preferences = this.getPreferences(this.options);
+		var timeout = 0;
+		var responseFilePath = dir + 'mock/' + expectedResponse + '.json';
+		var responseHeadersFilePath = dir + 'mock/' + expectedResponse + '.headers.json';
+
+		if (preferences && preferences.responseDelay) {
+			timeout = parseInt(preferences.responseDelay, 10);
+		}
+
+		if (expectedResponse === 'middleware') {
+			var middlewareResponse = this._acceptMiddleware(this.options, {
+				req: req,
+				res: res,
+				method: method,
+				dir: dir,
+				preferences: preferences,
+			});
+
+			if (typeof middlewareResponse === 'string') {
+				expectedResponse = middlewareResponse;
+				responseFilePath = dir + 'mock/' + expectedResponse + '.json';
+				responseHeadersFilePath = dir + 'mock/' + expectedResponse + '.headers.json';
+			} else {
+				return undefined;
+			}
+		}
+
+		return {
+			req: req,
+			res: res,
+			path: path,
+			method: method,
+			dir: dir,
+			expectedResponse: expectedResponse,
+			preferences: preferences,
+			timeout: timeout,
+			responseFilePath: responseFilePath,
+			responseHeadersFilePath: responseHeadersFilePath,
+		};
+	},
+
 	/**
 	 * @method _sendError
-	 * @param {object} options
+	 * @param {Object} options
 	 * @returns {void}
 	 * @private
 	 */
@@ -162,13 +214,16 @@ MockController.prototype = extend(MockController.prototype, {
 			status = parseInt(reg[3], 10);
 		}
 
-		options.res.statusCode = status;
+		if (options.res.statusCode === 200) {
+			options.res.statusCode = status;
+		}
+
 		options.res.send(this.readFile(options.responseFilePath));
 	},
 
 	/**
 	 * @method _sendError
-	 * @param {object} options
+	 * @param {Object} options
 	 * @returns {void}
 	 * @private
 	 */
@@ -186,7 +241,7 @@ MockController.prototype = extend(MockController.prototype, {
 
 	/**
 	 * @method _sendHead
-	 * @param {object} options
+	 * @param {Object} options
 	 * @returns {void}
 	 * @private
 	 */
@@ -229,7 +284,7 @@ MockController.prototype = extend(MockController.prototype, {
 
 	/**
 	 * @method _hasValidDynamicPathParam
-	 * @param {object} options
+	 * @param {Object} options
 	 * @returns {boolean}
 	 * @private
 	 */
@@ -267,9 +322,9 @@ MockController.prototype = extend(MockController.prototype, {
 
 	/**
 	 * @method _getResponseFiles
-	 * @param {object} options
-	 * @param {object} responseData
-	 * @returns {object}
+	 * @param {Object} options
+	 * @param {Object} responseData
+	 * @returns {Object}
 	 * @private
 	 */
 	_getResponseFiles: function (options, responseData) {
@@ -294,7 +349,7 @@ MockController.prototype = extend(MockController.prototype, {
 
 	/**
 	 * @method _getExpectedResponse
-	 * @param {object} req
+	 * @param {Object} req
 	 * @param {string} dir
 	 * @returns {string}
 	 * @private
@@ -324,7 +379,7 @@ MockController.prototype = extend(MockController.prototype, {
 	/**
 	 * @method _getFunc
 	 * @param {string|Array} path
-	 * @returns {object}
+	 * @returns {Object}
 	 * @private
 	 */
 	_getFunc: function (path) {
@@ -376,8 +431,8 @@ MockController.prototype = extend(MockController.prototype, {
 
 	/**
 	 * @method _getDynamicPathParams
-	 * @param {object} options
-	 * @returns {object}
+	 * @param {Object} options
+	 * @returns {Object}
 	 * @private
 	 */
 	_getDynamicPathParams: function (options) {
@@ -410,9 +465,9 @@ MockController.prototype = extend(MockController.prototype, {
 
 	/**
 	 * @method _getResponseData
-	 * @param {object} req
+	 * @param {Object} req
 	 * @param {string} method
-	 * @returns {object}
+	 * @returns {Object}
 	 * @private
 	 */
 	_getResponseData: function (req, method) {
@@ -452,8 +507,8 @@ MockController.prototype = extend(MockController.prototype, {
 	/**
 	 * @method _findFolder
 	 * @param {string} path
-	 * @param {object} options
-	 * @returns {object}
+	 * @param {Object} options
+	 * @returns {Object}
 	 * @private
 	 */
 	_findFolder: function (path, options) {
@@ -497,8 +552,8 @@ MockController.prototype = extend(MockController.prototype, {
 
 	/**
 	 * @method _writeDefaultHeader
-	 * @param {object} customHeaders
-	 * @param {object} res
+	 * @param {Object} customHeaders
+	 * @param {Object} res
 	 * @returns {void}
 	 * @private
 	 */
diff --git a/package.json b/package.json
index daf7873..81e7c27 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
 	"name": "node-mock-server",
-	"version": "0.12.1",
+	"version": "0.13.0",
 	"description": "File based Node REST API mock server",
 	"email": "simon.mollweide@web.de",
 	"author": "Simon Mollweide <simon.mollweide@web.de>",
diff --git a/readme.md b/readme.md
index 283f048..1c9493c 100755
--- a/readme.md
+++ b/readme.md
@@ -20,10 +20,11 @@
 - [Query params in mock data](/doc/readme-query-params.md)
 - [Dynamic path params in mock data](/doc/readme-path-params.md)
 - [Expected responses](/doc/readme-expected-response.md)
+- [Middleware responses](/doc/readme-middleware.md)
 - [Error cases](/doc/readme-expected-response.md)
 - [Swagger import](/doc/readme-swagger-import.md)
-    - DTO import
-    - DTO response function
+	- DTO import
+	- DTO response function
 - [Response validation](/doc/readme-response-validation.md)
 - [Response header](/doc/readme-response-header.md)
 - [DTO to Class converter](/doc/readme-dto-2-class.md)
@@ -59,30 +60,43 @@ var mockServer = require('node-mock-server');
 mockServer({
 	restPath: __dirname + '/mock/rest',
 	dirName: __dirname,
-    title: 'Api mock server',
-    version: 2,
-    urlBase: 'http://localhost:3003',
-    urlPath: '/rest/v2',
-    port: 3003,
-    funcPath: __dirname + '/func',
-    headers: {
-    	'Global-Custom-Header': 'Global-Custom-Header'
-    },
-    customDTOToClassTemplate: __dirname + '/templates/dto_es6flow.ejs',
-    swaggerImport: {
-    	protocol: 'http',
-    	authUser: undefined,
-    	authPass: undefined,
-    	host: 'localhost',
-    	port: 3001,
-    	path: '/src/swagger/swagger-demo-docs.json',
-    	dest: dest,
-    	replacePathsStr: '/v2/{baseSiteId}',
-    	createErrorFile: true,
-    	createEmptyFile: true,
-    	overwriteExistingDescriptions: true,
-    	responseFuncPath: __dirname + '/func-imported'
-    }
+	title: 'Api mock server',
+	version: 2,
+	urlBase: 'http://localhost:3003',
+	urlPath: '/rest/v2',
+	port: 3003,
+	funcPath: __dirname + '/func',
+	headers: {
+		'Global-Custom-Header': 'Global-Custom-Header'
+	},
+	customDTOToClassTemplate: __dirname + '/templates/dto_es6flow.ejs',
+	middleware: {
+		'/rest/products/#{productCode}/GET'(serverOptions, requestOptions) {
+			var productCode = requestOptions.req.params[0].split('/')[3];
+
+			if (productCode === '1234') {
+				requestOptions.res.statusCode = 201;
+				requestOptions.res.end('product 1234');
+				return null;
+			}
+
+			return 'success';
+		}
+	},
+	swaggerImport: {
+		protocol: 'http',
+		authUser: undefined,
+		authPass: undefined,
+		host: 'petstore.swagger.io',
+		port: 80,
+		path: '/v2/swagger.json',
+		dest: dest,
+		replacePathsStr: '/v2/{baseSiteId}',
+		createErrorFile: true,
+		createEmptyFile: true,
+		overwriteExistingDescriptions: true,
+		responseFuncPath: __dirname + '/func-imported'
+	}
 });
 ```
 
diff --git a/test/tests-mock-server.js b/test/tests-mock-server.js
index 9cabd5c..5a9b676 100755
--- a/test/tests-mock-server.js
+++ b/test/tests-mock-server.js
@@ -117,6 +117,26 @@ module.exports = function(serverOptions, _getFile) {
 		});
 	});
 
+	it('GET /products/{productCode} - with middleware', function (done) {
+		_fetch({
+			url: baseUrl + '/products/31221?_expected=middleware',
+			success: function (data) {
+				assert.equal(data, 'middware response');
+				done();
+			}
+		});
+	});
+
+	it('GET /products/{productCode} - with middleware 2', function (done) {
+		_fetch({
+			url: baseUrl + '/products/1234?_expected=middleware',
+			success: function (data) {
+				assert.equal(data, 'product 1234');
+				done();
+			}
+		});
+	});
+
 	it('GET /search/users/{userId}/products/{productCode}/available - with empty dynamic path param', function (done) {
 		_fetch({
 			url: baseUrl + '/search/users//products/1/available?_expected=success',
@@ -261,4 +281,4 @@ module.exports = function(serverOptions, _getFile) {
 	});
 
 
-};
\ No newline at end of file
+};
diff --git a/test/tests.js b/test/tests.js
index fccc055..4561054 100755
--- a/test/tests.js
+++ b/test/tests.js
@@ -23,6 +23,21 @@ serverOptions = {
 		'Global-Custom-Header': 'Global-Custom-Header'
 	},
 	customDTOToClassTemplate: __dirname + '/data/class-templates/dto_es6flow.ejs',
+	middleware: {
+		'/../demo/rest/products/#{productCode}/GET'(serverOptions, requestOptions) {
+
+			var productCode = requestOptions.req.params[0].split('/')[3];
+
+			if (productCode === '1234') {
+				requestOptions.res.statusCode = 201;
+				requestOptions.res.end('product 1234');
+				return null;
+			}
+
+			requestOptions.res.end('middware response');
+			return null;
+		}
+	},
 	swaggerImport: {
 		protocol: 'http',
 		dirName: __dirname,
diff --git a/views/method-modal.ejs b/views/method-modal.ejs
index d1b1a06..f809387 100755
--- a/views/method-modal.ejs
+++ b/views/method-modal.ejs
@@ -135,34 +135,36 @@
 							<label for="<%=service.id%><%=method.id%>_mockdown">
 								Choose an expected response:
 							</label>
-                            <% for(var m=0; m<method.availableMockResponses.length; m++) { %>
-                            	<% var mock = method.availableMockResponses[m]; %>
-                            	<% var checked = mock.isSelected ? 'checked' : ''; %>
-                            	<%
-                            		var label = '';
-                            		if (mock.isValidated) {
-                            			if (mock.isValid) {
-                            				label = '<span class="label label-success">Valid</span>';
-                            			} else {
-                            				label = '<span class="label label-danger">Invalid (' + mock.inValidCounter + ')</span>';
-                            			}
-                            		}
-                            	%>
-                            	<div class="radio">
-                                	<label>
-                                		<input
-                                			class="js-change-response-data"
-                                			data-path="<%=method.mockPath%>"
-                                			type="radio" <%-checked%>
-                                			name="<%=service.id%><%=method.id%>_mockdown"
-                                			id="<%=service.id%><%=method.id%><%=m%>"
-                                			value="<%=mock.name%>"
-                                		/>
-                                		<%-label%>
-                                		<%=mock.name%>
-                                	</label>
-                                	&nbsp;<a target="_blank" href="<%=urlBase%>/view/response?path=<%=encodeURIComponent(method.basePath);%>&method=<%=method.id%>&expected=<%=mock.name%>">preview</a>
-                                	<% if (mock.name.search(/error/) < 0) { %>
+							<% for(var m=0; m<method.availableMockResponses.length; m++) { %>
+								<% var mock = method.availableMockResponses[m]; %>
+								<% var checked = mock.isSelected ? 'checked' : ''; %>
+								<% var isMiddleware = mock.name.search(/^middleware$/) >= 0; %>
+								<% var isError = mock.name.search(/error/) >= 0; %>
+								<%
+									var label = '';
+									if (mock.isValidated && !isMiddleware) {
+										if (mock.isValid) {
+											label = '<span class="label label-success">Valid</span>';
+										} else {
+											label = '<span class="label label-danger">Invalid (' + mock.inValidCounter + ')</span>';
+										}
+									}
+								%>
+								<div class="radio">
+									<label>
+										<input
+											class="js-change-response-data"
+											data-path="<%=method.mockPath%>"
+											type="radio" <%-checked%>
+											name="<%=service.id%><%=method.id%>_mockdown"
+											id="<%=service.id%><%=method.id%><%=m%>"
+											value="<%=mock.name%>"
+										/>
+										<%-label%>
+										<%=mock.name%>
+									</label>
+									<% if (!isError && !isMiddleware) { %>
+										&nbsp;<a target="_blank" href="<%=urlBase%>/view/response?path=<%=encodeURIComponent(method.basePath);%>&method=<%=method.id%>&expected=<%=mock.name%>">preview</a>
 										<button
 											class="btn btn-primary btn-xs pull-right js-validate-single"
 											href="#"
@@ -172,9 +174,9 @@
 										>
 											Validate
 										</button>
-                                	<% }  %>
-                                </div>
-                            <% } %>
+									<% }  %>
+								</div>
+							<% } %>
 							<!--select
 									class="form-control js-change-response-data"
 									data-path="<%=method.mockPath%>"
@@ -213,4 +215,4 @@
 			</div>
 		</div>
 	</div>
-</div>
\ No newline at end of file
+</div>