express-openapi

An unopinionated OpenAPI framework for express

Highlights

Performant.
Extensively tested.
Unobtrusively opinionated.
Stays as close to express as possible.
Write API documentation in JSON or Yaml
- See args.apiDoc
Supports Promise based middleware and response handlers.
- See args.promiseMode
Supports Security Filtering
- See args.securityFilter
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
Leverages security definitions for security management.
- See express-openapi-security
Validates api documents.
- See openapi-schema-validation
Configurable Middleware.
- See Configuring Middleware
Supports custom format validators.
- See args.customFormats
Supports collectionFormat for formData array parameters.
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.
Supports TypeScript
- See Using with TypeScript
Supports external schema references
- See args.externalSchemas
Client SDK generators available.
- See fetch-openapi.
Adds apiDoc and operationDoc to requests E.G. req.apiDoc and req.operationDoc
Handles request payloads with consumes mimeTypes.
- See args.consumesMiddleware
Supports matching paths by regex to set security in operation docs.
- See args.pathSecurity

What is OpenAPI
Getting Started
Vendor Extensions
- Operation parameters
- Configuring Middleware
API
- .initialize(args)
Using with TypeScript
- Prerequisites
- TypeScript Example
Supported Versions of Node
License

What is OpenAPI?

The goal of the OAI specification is to define a standard, language-agnostic interface to REST APIs which allows both humans and computers to discover and understand the capabilities of the service without access to source code, documentation, or through network traffic inspection. When properly defined, a consumer can understand and interact with the remote service with a minimal amount of implementation logic. Similar to what interfaces have done for lower-level programming

To study the current specification view the docs.

Getting Started

To see example projects, look at our test suite.

This getting started guide will use the most fundamental concepts of OpenAPI and express-openapi.

Create your API's main apiDoc. You can create it anywhere. For this example we'll create it in under an api-v1/ directory:

// ./api-v1/api-doc.js

const apiDoc = {
  swagger: '2.0',
  basePath: '/v1',
  info: {
    title: 'A getting started API.',
    version: '1.0.0'
  },
  definitions: {
    World: {
      type: 'object',
      properties: {
        name: {
          description: 'The name of this world.',
          type: 'string'
        }
      },
      required: ['name']
    }
  },
  paths: {}
};

export default apiDoc;

You may be wondering why paths can be an empty object literal. We'll get to that in a second.

This is all that is required for our API's main apiDoc. To see the full list of values and options for the main apiDoc you can view The Schema.

Note: You can also use a YAML string instead of javascript objects e.g.

# ./api-v1/api-doc.yml
swagger: '2.0'
basePath: '/v1'
info:
  title: 'A getting started API.'
  version: '1.0.0'
definitions:
  World:
    type: 'object'
    properties:
      name:
        description: 'The name of this world.'
        type: 'string'
    required:
      - 'name'
paths: {}

Create path handlers.

Our paths object was empty in the main apiDoc because express-openapi will generate it for us based on the location of our path handlers. For this example we'll place our path handlers under api-v1/paths/.

Let's create a worlds path:

// ./api-v1/paths/worlds.js
export default function(worldsService) {
  let operations = {
    GET
  };

  function GET(req, res, next) {
    res.status(200).json(worldsService.getWorlds(req.query.worldName));
  }

  // NOTE: We could also use a YAML string here.
  GET.apiDoc = {
    summary: 'Returns worlds by name.',
    operationId: 'getWorlds',
    parameters: [
      {
        in: 'query',
        name: 'worldName',
        required: true,
        type: 'string'
      }
    ],
    responses: {
      200: {
        description: 'A list of worlds that match the requested name.',
        schema: {
          type: 'array',
          items: {
            $ref: '#/definitions/World'
          }
        }
      },
      default: {
        description: 'An error occurred',
        schema: {
          additionalProperties: true
        }
      }
    }
  };

  return operations;
}

In OpenAPI we define what operations a path exposes. Operations are exposed as HTTP methods.

The apiDoc property of the GET http method configures the getWorld operation with express-openapi. Without it express-openapi would do nothing with it. We can see that worldName is a required query parameter. If we were to call this operation without worldName we would receive a 400 input validation error.

In this example, we're also using dependency injection. This allows us to easily connect our path handlers with our API's services. We could've exposed an object literal instead of a function. The dependency injection approach is recommended which is why we use it here.

Create services

We referenced a worldsService in our path handler, let's create it now. It's best to place services that conform to your API's object definitions under a versioned folder. This keeps API versioned code separately and allows you to scale your app for multiple API versions.
```
// ./api-v1/services/worldsService.js

let worlds = {
  Earth: {
    name: 'Earth'
  }
};

const worldsService = {
  getWorlds(name) {
    return worlds[name] ? [worlds[name]] : [];
  }
};

export default worldsService;
```

Initialize your express app with express-openapi

We'll create our app file as usual and we'll initialize it with express-openapi:

// ./app.js
import express from 'express';
import openapi from 'express-openapi';
import v1WorldsService from './api-v1/services/worldsService';
import v1ApiDoc from './api-v1/api-doc';

const app = express();
openapi.initialize({
  app,
  // NOTE: If using yaml it's necessary to use "fs" e.g.
  // apiDoc: fs.readFilesync(path.resolve(__dirname, './api-v1/api-doc.yml'), 'utf8'),
  apiDoc: v1ApiDoc,
  dependencies: {
    worldsService: v1WorldsService
  },
  paths: './api-v1/paths'
});

app.listen(3000);

Our paths are now active and we can test them out with Swagger UI. This getting started guide didn't cover everything. For more examples see the sample projects used in our extensive test suite.

Vendor extensions

OpenAPI allows vendor extensions to be used throughout your api doc.

Operation parameters

'x-express-openapi-case-sensitive': false - Use this in parameter definitions to allow parameter names to be case insensitive. Use cases may include moving from a legacy application that didn't enforce case sensitivity (see #49).
```
GET.apiDoc = {
  ...
  parameters: [
    {
      name: 'paramName',
      in: 'query',
      type: 'string',
      required: true,
      'x-express-openapi-case-sensitive': false
    }
  ],
  ...
};
```
Calling this operation with paramname=5 will not affect the validity of the request and your path handler will receive paramName=5.

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.

'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 paths 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 or String	Y	This is an OpenAPI (swagger 2.0) compliant document. See the OpenAPI-Specification for more details.

args.apiDoc.paths can be an empty object. In that case express-openapi will populate this for you based on your operation level apiDocs. It is also possible to have just one central apiDoc.

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

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

You may pass a javascript object or a YAML string.

args.app

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

args.consumesMiddleware

Type	Required	Default Value	Description
Object	N	null	A key value map of mimeTypes and middleware.

Each key is the mime type from the consumes array of either the apiDoc or the operation doc.

var bodyParser = require('body-parser');
openapi.initialize({
  /*...*/
  consumesMiddleware: {
    'application/json': bodyParser.json(),
    'text/text': bodyParser.text()
  }
  /*...*/
});

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.dependencies

Type	Required	Description
Object	N	Mapping from keys to dependency objects that can be injected as named parameters into path handlers exported as functions

If not set, then all path handlers export an object. If set, then all path handlers export a constructor function whose signature may contain any of the keys in args.dependencies

Example

// ├── api-doc.js
// ├── api-paths1
// │   └── users.js
// ├── api-paths2
// │   └── location.js
// └── app.js

// app.js
// create some backend services. You can use typescript.

// a mock data provider, for testing or local development
var mockDataProvider = require("custom-mock-data-provider");

// a pretend geo service, as an example of allowing route handlers to perform external interactions
var geoService = require("awesome-geo-service")({url: "http.example.com/geoservice"});

openapi.initialize({
    apiDoc: require('./api-doc.js'),
    app: app,
    paths: [
        path.resolve(__dirname, 'api-paths'),
    ],

    // Provide a mapping of dependency names.
    // The keys of this object can be named parameters in the signature of
    // the functions exported from the modules in your paths directory.
    dependencies: {
        dataprovider: mockDataProvider(),
        geoservice: geoService
    }
});

// api-paths1/users.js
// inject both a dataprovider and geoservice dependency.
module.exports = function(geoservice, dataprovider) {
    var doc = {
        GET: function (req, res, next) {
            res.json({user: dataprovider.getUser(req.params.userid), location: geoservice.getUserLocation(req.params.userid)});
        }
    };
    doc.GET.apiDoc = {
        ...
    };
    return doc;
};


// api-paths2/location.js
// only inject a geoservice dependency.
module.exports = function(geoservice) {
    var doc = {
        GET: function (req, res, next) {
            res.json({location: geoservice.getUserLocation(req.session.user.id)});
        }
    };
    doc.GET.apiDoc = {
        ...
    };
    return doc;
};

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.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 */
  }
  /*...*/
});

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.externalSchemas

Type	Required	Default Value	Description
Object	N	null	Map id to pre-loaded external schema

This is used to resolve a schema reference $ref. Id can be a URL or relative path from args.docPath.

openapi.initialize({
  apiDoc: require('v3-api-doc'),
  /*...*/
  externalSchemas: {
    'http://example.com/schema': {
      description: "example schema",
      type: object,
      /*....*/
    },
    'http://example.com/another-schema': {
      /*....*/
    }
  }
  /*...*/
});

And then you can reference them in your api-doc file and route handlers.

{
  /*...*/
  parameters: {
    foo: {
      "in": "body",
      name: "foo",
      schema: { $ref: 'http://example.com/schema'}
    }
  },
  /*...*/
  definitions: {
   bar: { $ref: 'http://example.com/another-schema#/definitions/bar'}
  }
}

put.apiDoc = {
  /*...*/
  parameters: [
    {
      "in": "body",
      name: "foo",
      schema: { $ref: 'http://example.com/schema'}
    }
  ],
 /*...*/
}

args.pathSecurity

Type	Required	Default Value	Description
Array	N	null	An array of tuples.

Each tuple in the array consists of a RegExp to match paths, and a security definition (see security). The tuples are traversed in reverse order, so the bottom most matching RegExp wins. When a matching definition is found and the operation had no security defined, it is added to the operationDoc and security middleware is applied.

openapi.initialize({
  apiDoc: require('v3-api-doc'),
  /*...*/
  pathSecurity: [
    // here /some/{pathId} will get theirSecurity.
    [/^\/some/\{pathId\}/, [{mySecurity:[]}]],
    [/^\/some/\{pathId\}/, [{theirSecurity:[]}]]
  ]
  /*...*/
});

args.paths

Type	Required	Description
String or Array	Y	Relative path or paths to the directory or directories that contain your route files or route specifications.

Path 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 paths 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 paths directory as follows:

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

The contents of <project>/paths/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:
    GET
    DELETE
    PATCH
    OPTIONS
    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 = {
  /* ... */
};

Alternatively, args.paths may contain route specifications of the form { path: '/foo/{id}', module: require('./handlers/foo') }.

Modules under args.paths 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.pathsIgnore

Type	Required	Description
RegExp	N	Paths matching this regular expression will be ignored.

A common use for this is to ignore spec or test files located in the same folder than the paths, like:

openapi.initialize({
  apiDoc: apiDoc,
  app: app,
  paths: './api-v1/paths',
  pathsIgnore: new RegExp('\.(spec|test)$')
})

args.promiseMode

Type	Required	Default Value	Description
Boolean	N	false	Allows middleware and path handlers to return promises.

The following would then be supported:

export default function(worldsService) {
  const operations = {
    GET,
    PUT,
  };

  // If using node >= 7.6 you can use async/await.
  async function GET(req, res) {
    const worlds = await worldsService.getWorlds(req.query.worldName);
    if (!worlds.length) {
      throw {
        status: 404,
        message: 'No worlds were found',
      };
    }
    res.status(200).json(worlds);
  }

  // For node < 7.6 you can use plain promises.
  function PUT(req, res) {
    return worldsService.getWorlds(req.query.worldName)
      .then(function(worlds) {
        if (!worlds.length) {
          throw {
            status: 404,
            message: 'No worlds were found',
          };
        }
        res.status(200).json(worlds);
      });
  }

  /* apidocs removed for brevity's sake in this example. */

  return operations;
}

args.securityFilter

Type	Required	Default Value	Description
Function	N	null	Request handler for the api doc route.

req.apiDoc will be set to a copy of the generated api doc and the securityFilter is free to modify it. This is useful if you're implementing Security Filtering.

Note: You must end the request inside the filter.

openapi.initialize({
  /* ... */
  promiseMode: true,
  securityFilter: async (req, res) => {
    // do something, use await, whatever
    if (!req.user) {
      // only show paths to logged in users.
      req.apiDoc.paths = {};
    }
    res.status(200).json(req.apiDoc);
  }
});

args.securityHandlers

Type	Required	Default Value	Description
Object	N	null	Map name of security scheme name to a handler function.

If you'd like to support security, define your schemes in your apiDoc like so:

var apiDoc = {
  swagger: 2.0,
  /* ... */
  securityDefinitions: {
    keyScheme: {
      type: 'apiKey',
      name: 'api_key',
      in: 'header'
    },
    passwordScheme: {
      type: 'basic'
    }
  }
};

Next you can define your security handlers in the OpenAPI initialization args:

openapi.initialize({
  apiDoc: apiDoc,
  app: app,
  securityHandlers: {
    keyScheme: function(req, scopes, definition, cb) {
      /* do something.  You can assign values to req to make them available in
      operation handlers. */
      cb(null, true);
    },
    passwordScheme: function(req, scopes, definition, cb) {
      /* do something */
      cb({
        status: 401,
        challenge: 'Basic realm=foo',
        message: 'You must authenticate to access foo.'
      });
    }
  }
});

Now you can use security in your operation docs, or in the api doc.

module.exports = {
  post: post
};

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

post.apiDoc = {
  /* ... */
  security: [
    {
      passwordScheme: []
    },
    // if the previous set of security schemes fail, we move to the next block.
    {
      keyScheme: []
    }
  ]
};

See express-openapi-security for more details.

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`.

Using with TypeScript

This package includes definitions for TypeScript.

Prerequisites

Install definitions for express and body-parser(optional) via typings.

TypeScript Example

In server script:

import * as express from "express";
import * as bodyParser from "body-parser";
import * as openapi from "express-openapi";

var app = express();

app.use(bodyParser.json());

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

app.use(<express.ErrorRequestHandler>(err, req, res, next) => {
    res.status(err.status).json(err);
});

app.listen(3000);

In route handler file like <project>/src/api-paths/users/{id}.ts:

import {Operation} from "express-openapi";

export var parameters = [
  {
    in: 'path',
    name: 'id',
    required: true,
    type: 'integer'
  }
 ];

export var get: Operation = [
    /* business middleware not expressible by OpenAPI documentation goes here */
    (req, res, next) => {
        res.status(200).json(/* return the user */);
    }
];

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'
    }
  }
};

export var post: Operation = (req, res, next) => {
    /* ... */
}

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

Supported Versions of Node

node@<=0.12.x => express-openapi@<=1.3.x
node@>0.12.x => express-openapi@*

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.

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