swagger-routes
Generate Express or Restify route handlers from a Swagger specification
Last updated 10 months ago by mikestead .
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Swagger Routes

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A tool to generate and register Restify or Express route handlers from a Swagger 2.0 (OpenAPI) specification.

Usage

Requires Node v4.0+

Express

const swaggerRoutes = require('swagger-routes')
const express = require('express')
const app = express()

swaggerRoutes(app, {
    api: './api.yml',
    handlers:  './src/handlers',
    authorizers: './src/handlers/security'
})
app.listen(8080)

Restify

const swaggerRoutes = require('swagger-routes')
const restify = require('restify')
const server = restify.createServer()

swaggerRoutes(server, {
    api: './api.yml',
    handlers:  './src/handlers',
    authorizers: './src/handlers/security'
})
server.listen(8080)
Options
  • api: path to your Swagger spec, or the loaded spec reference.
  • docsPath: url path to serve your swagger api json. Defaults to /api-docs.
  • docsMiddleware: An optional middleware function that can be used to secure the api docs endpoint.
  • handlers: directory where your handler files reside. Defaults to ./handlers. Can alternatively be a function to return a handler function given an operation.
  • authorizers: directory where your authorizer files reside. Defaults to ./security. Can alternatively be a function to return an authorizer middleware given a swagger security scheme.
  • maintainHeaders: Keeps your generated handler doc headers in sync with your Swagger api. Default is false.

Operation Handlers

You have the option to define and maintain a handler file for each Swagger operation, or alternatively provide a factory function which creates a handler function given an operation.

Handler Files

Using individual handler files is a good choice if each handler needs unique logic to deal with an operation request.

A handler file must be named after the Swagger operation it handles e.g. listPets.js.

All handler files must reside in the same directory, unless the group option is enabled, in which case the handler file should sit under a folder of its primary tag name (see Generating Handler Files below).

File Contents

A function called handler should be exported to deal with an incoming operation request.

exports.handler = function listPets(req, res, next) {

}

You also have the option to export a middleware function to be executed before the handler.

exports.middleware = preprocess

function preprocess(req, res, next) {
    next()
}

Middleware can be an ordered list.

exports.middleware = [
    function preprocess1(req, res, next) { next() },
    function preprocess2(req, res, next) { next() }
]
Generating Handler Files

To save you some time there's a bundled tool to generate handler files based on operations in your Swagger spec, together with a Mustache template.

This tool is on by default so check your handlers folder the first time you run swaggerRoutes and it should be poulated with handler stubs for each operation defined in your Swagger document.

Each time you start your app swaggerRoutes will see if you have any missing operation handlers and generate stub handler for any which are. If a handler file exists it won't be touched, i.e. this is non-destructive so you are free to edit them.

Note that if you turn on the syncHeaders option then the header of your handler files will be updated each run based on your Swagger api. This keeps your handler documentation up to date so you can easily see what parameters accompany a request for a given operation. It will overwrite any edits you make to the header so only turn on if you don't plan on manually editing them.

When a re-run finds handlers no longer in use they will be renamed with an _ prefix, so listPets.js would become _listPets.js. This allows you to identify handlers no longer in use and remove / rename them if you wish.

If you later enable a handler again in your spec and re-run, then the underscore will be removed.

Note that this feature of prefixing removed handlers is only currently supported when the group options is not enabled.

The default template is defined here but you can supply your own by expanding the handlers option e.g.

{
    ...
    handlers: {
        path: './src/handlers',
        template: './template/handler.mustache', // can also be set with a loaded template
        getTemplateView: operation => operation, // define the object to be rendered by your template
        create: operation => (req, res) => {}, // see Handler Factory section for details
        generate: true, // hander file generation on by default
        group: false // when true each handler file will be placed under a directory named after its primary tag
    }
}

Handler Factory

The factory function is a better option to a file if handlers are quite similar e.g. delegate their request processing onto service classes.

Creating a Handler Factory

You can define handlers as a function when registering your routes. It receives a Swagger operation and returns the request handler responsible for dealing with it.

const swaggerRoutes = require('swagger-routes')

swaggerRoutes(app, {
    api: './api.yml',
    handlers:  createHandler
})

function createHandler(operation) {
    return function handler(req, res, next) {
        res.send(operation.id)
    }
}

If a handler function is returned then it will take precedence over a handler file for the same operation.

Route Middleware

Just as a file handler can define route middleware, so can createHandler.

function createHandler(operation) {
    return {
        middleware: function preprocess(req, res, next) { next() },
        handler: function handler(req, res, next) { res.send(operation.id) }
    }
}

As before, route middleware can be an ordered list.

function createHandler(operation) {
    return {
        middleware: [
            function preprocess1(req, res, next) { next() },
            function preprocess2(req, res, next) { next() }
        ],
        handler: function handler(req, res, next) { res.send(operation.id) }
    }
}

Authorizers

When your Swagger api specifies one or more security schemes then routes which opt into one or more of these schemes can be protected by authorizer middleware.

Just like handlers, you can define an authorizer in a file or via a factory.

File Authorizer

The file should be named after the security scheme it protects e.g. petstore_auth.js, and reside in the directory path defined by the authorizers option. It should export a single middleware function to authorize a request.

module.exports = function petstore_auth(req, res, next) {
    const token = decodeToken(req.headers.authorization)
    if (token) {
        const scopes = getTokenScopes(token)
        next(req.verifyScopes(scopes))
    } else {
        const error = new Error('Unauthorized')
        error.status = error.statusCode = 401
        next(error)
    }
}

The above is one example of how this can work.

As you can see a verifyScopes function is supplied to the req if the security scheme is OAuth2. It takes an array of scopes you decode from the authenticated request and verifies that the required scope(s) defined be the scheme are present. If they're not a 403 Forbidden error is returned.

When multiple oauth scopes are defined for the security of an endpoint, Swagger expects all of them to be present for a call to proceed. As an extension to this, swagger-routes also supports the logical OR of token scopes, so if any exist then verifyScopes succeeds.

As an example, this definition below will pass the auth check if either a Catalog OR Playback scope exist.

  ...
  security:
    - accountAuth:
      - Catalog
      - Playback
  x-security:
    accountAuth:
      OR_scopes: true

Remember if no credentials are supplied a 401 Unauthorized should be returned.

Generating Authorizer Files

Much like handler files, authorizer file stubs will be generated and managed for you too.

The default template is defined here but you can supply your own by expanding the authorizers option e.g.

{
    ...
    authorizers: {
    	path: './src/handlers/security',
    	template: './template/authorizer.mustache', // can also be set with a loaded template
    	getTemplateView: operation => operation, // define the object to be rendered by your template
    	create: operation => (req, res) => {}, // see Authorizer Factory section for details
    	generate: true // authorizer file generation on by default
    }
}

Authorizer Factory

const swaggerRoutes = require('swagger-routes')

swaggerRoutes(app, {
    api: './api.yml',
    authorizers: createAuthorizer
})

function createAuthorizer(schemeId, securityScheme) {
    return function authorizer(req, res, next) {
        const token = decodeToken(req.headers.authorization)
        if (token) {
            const scopes = getTokenScopes(token)
            next(req.verifyScopes(scopes))
        } else {
            const error = new Error('Invalid access token')
            error.status = error.statusCode = 401
            next(error)
        }
    }
}

Request Validation

Each incoming request which makes it to a handler will be run through request validation middleware. This executes JSON Schema validation on the request to ensure it meets the Swagger specification you've defined. A failure to meet this requirement will cause the request to fail and the handler not to be executed.

Swagger Host

Statically setting the host property of your Swagger api can be error prone if you run the api in different environments (QA, Staging, Production), that's why I'd recommended removing its definition from your specification. This will by default then resolve to the host, including port, the spec is served from.

If this still isn't sufficient you have a couple of other options.

  1. Set API_HOST environment variable for your node instance. SwaggerRoutes will pick this up and use it.
  2. Set the app.swagger.host manually from within your app after you've called swaggerRoutes.
const server = app.listen(3000, '0.0.0.0', () => {
    app.swagger.host = `${server.address().address}:${server.address().port}`
})

Route Stack Execution Order

  1. authorizer middleware If there are security restrictions on a route then an authorizer for each will need to verify the rights attached to the request.
  2. custom middleware If the route defines one or more middleware these will be executed in order.
  3. validation middleware The incoming request will now be validated against the Swagger spec for the given operation.
  4. handler Assuming all previous steps pass, the handler is now executed.

Advanced Usage

Registering Multiple Swagger Apis

You may be in the situation where you have a Swagger definition for each major version of your api. If this is the case, and you want to handle each on the same server, then you are free to register more than one spec.

swaggerRoutes(server, {
    api: './api-v1.yml',
    handlers:  './src/handlers/v1',
    authorizers: './src/handlers/v1/security'
})

swaggerRoutes(server, {
    api: './api-v2.yml',
    handlers:  './src/handlers/v2',
    authorizers: './src/handlers/v2/security'
})

You'll need to ensure that there's no conflict in route paths between each. The best way to do that would be to add a unique basePath to each spec, say /v1, /v2 etc.

Operation Object

An operation object inherits its properties from those defined in the Swagger spec.

There are only a few differences / additions.

  • id: Replaces operationId.
  • path: The route path of this operation.
  • method: The http method
  • consumes: Populated with the top level consumes unless the operation defines its own.
  • produces: Populated with the top level produces unless the operation defines its own.
  • paramGroupSchemas: JSON Schema for each param group ('header', 'path', 'query', 'body', 'formData') relevant to the operation.

Acknowledgments

Inspiration for this library came primarily from time spent using swaggerize-express. It's a great library which you should check out.

My reasoning behind writing a new, alternate implementation was the wish to base all routing off operation ids and not paths. This aligns with how Swagger client code gen works, making it easier to see your client SDKs and server code base as a whole.

I also wanted to automate away much of the boilerplate code being written and support Restify and Express in a single library, given their similarities.

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