express-openapi

Effortlessly add routes and middleware to express apps with openapi documents.

Highlights

• Utilizes convention based programming.
• Unobtrusively opinionated.
• Stays as close to express as possible.
• Leverages openapi parameter lists for parameter defaults, type coercion, and validation.
  • See express-openapi-defaults
  • See express-openapi-coercion
  • See express-openapi-validation
• Leverages openapi response definitions to provide res.validateResponse tailored to a particular route.
  • See express-openapi-response-validation
• Validates api documents.
  • See openapi-schema-validation
• Configurable Middleware.
  • See Configuring Middleware
• Performant.
• Supports custom format validators.
  • See args.customFormats
• Supports collectionFormat for formData array parameters.
• Extensively tested.
• Small footprint.
• Currently supports openapi 2.0 (f.k.a. swagger 2.0) documents.
• Conforms to the single responsibility principle.
• Clean interface.
• Supports error middleware scoped to your API's basePath.
  • See args.errorMiddleware
• Adds a route for Swagger UI (apiDoc.basePath + args.docsPath).
• Adds operation tags to your apiDoc.tags array and sorts them alphabetically for you.
  • See how it's done in the basic-usage sample project.

Example

Let's use the sample project located at ./test/sample-projects/basic-usage/.

The project layout looks something like this:

Here's how we add our routes to express:

var app = require('express')();
var bodyParser = require('body-parser');
var openapi = require('express-openapi');
var cors = require('cors');

app.use(cors());
app.use(bodyParser.json());

openapi.initialize({
  apiDoc: require('./api-doc.js'),
  app: app,
  routes: './api-routes'
});

app.use(function(err, req, res, next) {
  res.status(err.status).json(err);
});

app.listen(3000);

Our routes are now active and we can test them out with Swagger UI:

For more examples see the sample projects used in tests.

Configuring Middleware

You can directly control what middleware express-openapi adds to your express app by using the following vendor extension properties. These properties are scoped, so if you use one as a root property of your API Document, all paths and operations will be affected. Similarly if you just want to configure middleware for an operation, you can use these properties in said operation's apiDoc. See full examples in the ./test/sample-projects/ directory.

Supported vendor extensions

• 'x-express-openapi-additional-middleware': [myMiddleware] - Adds the provided middleware after defaults, coercion, and validation middleware (added by express-openapi) but before middleware defined in operations. This property inherits from all previous properties.
• 'x-express-openapi-inherit-additional-middleware': false - Prevents middleware added in a parent scope with x-express-openapi-additional-middleware. This extension works from the methodDoc up to the apiDoc, as opposed to the apiDoc down to the methodDoc. The effect is that using this extension in the methodDoc would prevent that method from receiving any additional middleware defined in parent scopes. You can use this extension in any scope (methodDoc, pathDoc, or apiDoc) and the result i the same.
• 'x-express-openapi-disable-middleware': true - Disables all middleware.
• 'x-express-openapi-disable-coercion-middleware': true - Disables coercion middleware.
• 'x-express-openapi-disable-defaults-middleware': true - Disables defaults middleware.
• 'x-express-openapi-disable-response-validation-middleware': true - Disables response validation middleware I.E. no res.validateResponse method will be available in the affected operation handler method.
• 'x-express-openapi-disable-validation-middleware': true - Disables input validation middleware.

API

.initialize(args)

Initializes routes and middleware on an express app, and returns an initialized api. An initialized api contains the following properties:

• apiDoc - This is the final result of the apiDoc after processing.

args.apiDoc

Type	Required	Description
Object	Y	This is an openapi (swagger 2.0) compliant document. See the OpenAPI-Specification for more details.

args.apiDoc.paths should be an empty object. express-openapi will populate this for you. This prevents you from defining your paths in 2 places.

args.apiDoc.basePath will add a prefix to all routes added by express-openapi.

args.apiDoc.definitions will be used for de-referencing $ref properties in parameters.

args.app

Type	Required	Description
Object	Y	The express app you wish to initialize.

args.routes

Type	Required	Description
String	Y	A path to the directory that contains your route files.

Route files are logically structured according to their URL path. For cross platform compatibility, URLs that accept a parameter use the swagger format for parameters as opposed to the express format (i.e. use {id} instead of :id). Filenames in Windows do not allow the : character as it is confused with drive names.

For example, if you have the following api routes that you wish to add to your express app:

GET /v1/users/{id}
POST /v1/users

You would define basePath: '/v1' in your apiDoc, and layout your routes directory as follows:

<project>
        `routes/
               `users/
                     `{id}.js
                users.js

The contents of <project>/routes/users/{id}.js would look like this:

module.exports = {
  // parameters for all operations in this path
  parameters: [
    {
      in: 'path',
      name: 'id',
      required: true,
      type: 'integer'
    }
  ],

  /*
    Also available are:
    del
    delete
    patch...
    see index.js for the full list.
  */

  get: [
    /* business middleware not expressible by openapi documentation goes here */
    function(req, res, next) {
      var validationError = res.validateResponse(200, /* return the user or an error */);

      if (validationError)
        return next(validationError);
      }

      res.status(200).json(/* return the user or an error */);
    }
  ],

  post: post
};

module.exports.get.apiDoc = {
  description: 'A description for retrieving a user.',
  tags: ['users'],
  operationId: 'getUser',
  // parameters for this operation
  parameters: [
    {
      in: 'query',
      name: 'firstName',
      type: 'string'
    }
  ],
  responses: {
    default: {
      $ref: '#/definitions/Error'
    }
  }
};

function post(req, res, next) {
  /* ... */
}

post.apiDoc = {
  /* ... */
};

Modules under args.routes expose methods. Methods may either be a method handler function, or an array of business specific middleware + a method handler function.

express-openapi will prepend middleware to this stack based on the parameters defined in the method's apiDoc property. If no apidoc property exists on the module method, then express-openapi will add no additional middleware.

args.docsPath

Type	Required	Default Value	Description
String	N	/api‑docs	Sets the path that Swagger UI will use to request args.apiDoc with populated paths. You can use this to support multiple versions of your app.

args.errorTransformer

Type	Required	Description
Function	N	Transforms errors to a standard format as defined by the application. See express-openapi-validation#args.errorTransformer and express-openapi-response-validation for more info.

args.exposeApiDocs

Type	Required	Default Value	Description
Boolean	N	true	Adds a route at args.apiDoc.basePath + args.docsPath. The route will respond with args.apiDoc.

args.validateApiDoc

Type	Required	Default Value	Description
Boolean	N	true	Validates args.apiDoc before and after path population. This does not effect individual route validation of route parameters. You can disable this behavior by passing false.

args.customFormats

Type	Required	Default Value	Description
Object	N	null	An object of custom formats.

Each key is the name of the format to be used with the format keyword. Each value is a function that accepts an input and returns a boolean value.

openapi.initialize({
  /*...*/
  customFormats: {
    myFormat: function(input) {
      return input === 'foo';
    }
  }
  /*...*/
});

See Custom Formats in jsonschema.

args.errorMiddleware

Type	Required	Default Value	Description
Object	N	null	A middleware function that is scoped to your api's basePath.

This is just standard express error middleware (I.E. it has 4 arguments err, req, res, next). When an error occurs in your API's handlers, it'll be passed to this middleware. The rest of your app is unaffected.

openapi.initialize({
  apiDoc: require('v3-api-doc'),
  /*...*/
  errorMiddleware: function(err, req, res, next) { // only handles errors for /v3/*
      /* do something with err in a v3 way */
  }
  /*...*/
});

LICENSE

The MIT License (MIT)

Copyright (c) 2016 Kogo Software LLC

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.