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Expressive

Fast, opinionated, minimalist, and conventional REST API framework for node. (With Typescript Support ⭐)

*Table of contents generated with markdown-toc

Introduction

Expressive is a NodeJS REST API framework built on ExpressJs and best practices for smooth development. Features include:

  • Templated Routing
    • Write APIs with declarative endpoints (including nested endpoints) easily
  • Pluggable middleware with built-ins
    • Inject own middleware just like Express
    • Built in middleware e.g. body-parser, cors, etc.
    • Security middleware i.e. helmet
  • Built in support for asynchronous request handlers and middleware
    • No need to wrap every controller with a try/catch block. Any error thrown will be sent to a central error handler
  • Implicit next function calls
    • If you do not declare the next variable in your handler function, then it will be called for you automatically after your handler executes. If you declare it as a function parameter, you can use it as you like.
  • API validation using celebrate with Joi schemas (Using Joi schemas also yields generated Swagger documentation!)
  • Centralized error handling
    • All errors thrown in controller functions will go into one user-defined error middleware function (can be defined with app constructor)
  • REST standard responses e.g. 200, 201, 404 built-in with the BaseController class methods
  • Centralized authorization
    • By defining authorizer function at any level - app, subroute, or route
    • Objective Authorization: By defining an authorizer object for each level, and centrally managing request authorization with one handler
  • Doc generation through Swagger https://swagger.io/
    • Request parameter docs are generated if validationSchema property is provided with Joi schemas!
    • Each endpoint can have an associated doc using Swagger syntax (JSON/JS), making doc writing easier and distributed.
    • Swagger doc can be viewed in development at http://localhost:8080/docs
  • Monitoring with express-status-monitor

Quickstart

Install the package: npm i -S @siddiqus/expressive

Here is a basic example: *It is required for controllers to extend BaseController. This also allows for dependencies to be instantiated inside the constructor, which can be useful for testing.

import { Route, ExpressApp, BaseController, ExpressiveRouter } from '@siddiqus/expressive';

class HelloGetController extends BaseController {
  handleRequest(req, res) {
    this.ok({
      hello: 'world'
    });
  }
}

const router: ExpressiveRouter = {
  routes: [Route.get('/hello', new HelloGetController())]
};

const app = new ExpressApp(router);
const port = Number(process.env.PORT || 8080);
app.listen(port, () => console.log('Listening on port ' + port));

Run this node script will start an Express app on port 8080. A GET request on [http://localhost:8080/hello] will return the following JSON response

{
  "hello": "world"
}

The ExpressJS app can be used from the express property of the app object e.g. app.express

*It is not recommended to write your whole application in one file like the one above. Please see the example folder for a sample folder structure for your application.

Migrating from V3 to V4

V4 has two main differences from V3:

  1. Controller classes need to be initialized when creating a Route object, which allows for dependency injection.
  2. Route properties e.g. validationSchema, middleware, authorizer, doc etc. need to be set as class properties of the controller.

V3 example

import { ExpressiveRouter, BaseController, Route } from '@siddiqus/expressive';

class HelloController extends BaseController {
    // some implementation of handleRequest
}
const router: ExpressiveRouter = {
    routes: [
        Route.get(
            '/hello',
            HelloController, // controller is not initialized here
            {
                validationSchema: { }, // some validation schema object
                authorizer: { }, // some authorizer object
                middleware: [(req, res) => {}], // some middleware functions
                doc: someDocJs // some swagger definition
            }
        )
    ]
}

V4 example

import { ExpressiveRouter, BaseController, Route } from '@siddiqus/expressive';

// declare validationSchema, middleware, etc. as class properties
class HelloController extends BaseController {
    validationSchema = { }, // some validation schema object
    authorizer = { }, // some authorizer object
    middleware = [(req, res) => {}], // some middleware functions
    doc = someDocJs // some swagger definition
    
    // some implementation of handleRequest
}
const router: ExpressiveRouter = {
    routes: [
        Route.get('/hello', new HelloController(dependencies)) // HelloController class needs to be initialized with dependencies if any
    ]
}

Routing

It is easy to create routes and nested routes using Expressive, with the focus being on each individual endpoint.

The BaseController

Each separate endpoint e.g. 'GET /users/:userId' is handled using a controller class, that extends the BaseController class provided by Expressive. There is an 'abstract' method called handleRequest that requires an implementation for your own controller. The Express request, response and next objects are available in this method using this. This handleRequest method can be used as an async function also. For example:

const { BaseController } = require('@siddiqus/expressive');

class GetUsersController extends BaseController {
  constructor(usersRepository) {
    this.usersRepository = usersRepository;
  }
  async handleRequest() {
    const userId = this.req.params.userId; // get an id from the path parameter
    const userData = await this.usersRepository.getUserById(userId);
    this.ok(userData); // base methods available for HTTP responses
  }
}

Here you'll notice that the request object is available with this.req and you can send a JSON response using the this.ok function. This function sends back the data with a 200 status code. There are more methods implemented for various HTTP actions e.g.

  • created (201)
  • accepted (202)
  • noContent (204)
  • badRequest (400)
  • unauthorized (401)
  • forbidden (403)
  • notFound (404)
  • tooMany (429)
  • internalServerError (500)
Wrapping request and response data

Sometimes you will want to always wrap your request/response data e.g. response: { data: someData } The BaseController class has static methods responseMapper and requestMapper which have the response data and request object as a parameter respectively. The responseMapper is used in the class methods e.g. this.ok(data) etc. to always wrap your response the way you define it. The requestMapper can be used to do any high level request mapping for your application. You can overwrite this in your startup files like app.ts like so:

import { BaseController, ExpressiveRouter, Route } from '@siddiqus/expressive'

BaseController.responseMapper = (data) => {
  return {
    body: data,
  }
}
BaseController.requestMapper = (req) => {
  // here normalizePhone is a utility function
  req.body.phoneNumber = normalizePhone(req.body.phoneNumber) || undefined;
  return req;
}

const router = {
    routes: [] // route list
}
const app = new ExpressApp(router);

Routes and subroutes

  • The ExpressApp class takes a 'router' parameter in its constructor's first parameter. This 'router' object looks like this:

    {
    routes: [],
    subroutes: []
}

  • Each object in the routes array is an instance of the Route class. For example, we can use the Route class's GET method to create a GET endpoint like so:

    const { Route } = require('@siddiqus/expressive');

const helloGetRoute = Route.get(
  '/some/path', // required - relative end path of endpoint
  new SomeController(), // required - a controller function or class
);

    Similarly, the class methods post, put, delete, patch, head, and options are available for the Route class e.g. Route.post.

  • Each object in the subroutes array can be constructed using the subroute function, like so:

    const { subroute } = require('@siddiqus/expressive');

const router = {
  subroutes: [
    subroute('/some/sub/path', someRouter) // 'someRouter' is another router object
  ]
};

Yes, the router object is recursive ;)

Routing Example

Let's say we want to create an API with the following routes:

  • GET /
  • GET /hello/
  • GET /hello/users
  • POST /hello/users

We need to define a router object as follows:

const { Route, subroute } = require('@siddiqus/expressive');

const helloRouter = {
  routes: [
    // with some predefined controller functions
    Route.get('/', new GetHelloController()),
    Route.get('/users', new GetUsersController()),
    Route.post('/users', new CreateUsersController())
  ]
};

const apiRouter = {
  routes: [
    Route.get('/', new ApiRootController()) // some predefined controller
  ],
  subroutes: [subroute('/hello', helloRouter)]
};

Express App Configuration

The ExpressApp class constructor's second parameter is a configuration object that looks like this:

{
  (swaggerInfo = null), // this is an optional JSON with the basic swagger info detailed later
    swaggerDefinitions, // this is an optional JSON for the swagger model definitions
    (allowCors = false), // this uses the 'cors' npm module to allow CORS in the express app, default false
    (corsConfig = null), // config for cors based on the 'cors' npm module, allows all origin by default
    (middleware = null), // Array of express middlewares can be provided (optional)
    (errorHandler = null), // express middleware function to handle errors e.g. function(err, req, res, next){}
    (basePath = '/'), // Root path of the api, default "/"
    (bodyLimit = '100kb'),
    (helmetOptions = null), // options for the 'helmet' middleware
    (celebrateErrorHandler = null), // optional, handler to replace default celebrate 'errors' middleware
    (notFoundHandler = null), // optional, handler that runs after all routes. By default it returns 404 status with a message.
    (authObjectHandler = null); // optional handler to manage authorization via authorizer objects. See 'Centralized authorization' below.
}

Middleware configuration

Expressive comes with some built-in middleware at the application level. Middlware can be defined at any level - the application level (top), the route level (individual endpoint), and the subroute level (group of endpoints). Bear in mind since the routes follow a hierarchical structure, the middleware will be executed in the order of:

  1. route level
  2. subroute level
  3. ExpressApp level

So please be aware of using the next() function accordingly inside your middleware.

Built-in Middleware

The Expressive app comes with the following built-in middleware:

  • cors - Allow CORS requests
  • express-request-id - Assign a unique ID for each request
  • helmet - Add various HTTP headers for basic security
  • json and urlencoded from the express module (previously deprecated from body-parser)

CORS

You can enable CORS through the cors module using Expressive like this:

const app = new ExpressApp(router, {
  allowCors: true
});

This will allow CORS for all origins. If you want to configure CORS as per the module's documentation, you can do so with the 'corsConfig' parameter:

const app = new ExpressApp(router, {
  allowCors: true,
  corsConfig: {
    origin: 'http://example.com',
    optionsSuccessStatus: 200 // some legacy browsers (IE11, various SmartTVs) choke on 204
  }
});

Security features with Helmet

The helmet middleware is enabled with default configuration, and can be configured manually through the ExpressApp constructor, like so:

const app = new ExpressApp(router, {
  helmetConfig: {
    // some helmet configuration, see https://www.npmjs.com/package/helmet
  }
});

Configuring your own middleware

These are examples on how to declare middleware accross the Expressive application.

At the route level

const { BaseController, ExpressApp } = require('@siddiqus/expressive');

class GetHelloController extends BaseController {
    middleware = [someMiddlewareForHello] // some array of middleware to execute for this particular endpoint
    handleRequest() {
        this.ok({
            hello: 'world'
        })
    }
}

const router = {
  routes: [
    Route.get('/hello', new GetHelloController())
  ]
};

const app = new ExpressApp(router);

At the sub route level

const { subroute } = require('@siddiqus/expressive');

const router = {
  subroutes: [
    subroute('/hello', someHelloRouter, {
      middleware: [] // some array of middleware to execute for all routes under /hello
    })
  ]
};

At the application level

const expressApp = new ExpressApp(router, {
  middleware: [] // some array of middleware
});

Point to note, these middleware functions run right before the main request handler for the given route

Centralized error handling

To catch an error from any controller, pass an error handling function using the 'errorHandler' property in the options parameter for the ExpressApp constructor. For example:

const { ExpressApp } = require("@siddiqus/expressive");

function centralizedErrorHandling (err, req, res, next) {
    res.status(500);
    res.json({
        message: "There was an internal error."
    });
}

const app = new ExpressApp(router, {
  errorMiddleware: centralizedErrorHandling // all errors go here, can also be an array
}

It is recommended that you define custom Error classes to throw from inside your controllers, and then handle them in a switch in your central error handler.

Asynchronous request handlers and middleware

Expressive does some work under the covers to manage async request handlers as well as async middleware.

Handling requests

In any controller (that extends the BaseController of course), you can declare the handleRequest function as async, but this is optional. So both of these are okay:

class SomeController extends BaseController {
  handleRequest(req, res, next) {
    // some non-async code
  }
}

And this is also okay:

class SomeController extends BaseController {
  async handleRequest(req, res, next) {
    // some async code
  }
}

Middleware

This example shows both async and non-async middleware being passed to multiple levels e.g. routes and subroutes.

const someMiddlewareForGetHello = [
  async (req, res, next) => console.log('from mid 1') || next(), // this works
  (req, res, next) => console.log('from mid 2') || next(), // this works too
  (req, res) => console.log('from mid 2') // this works too
]

class GetHelloController extends BaseController {
    middleware = someMiddlewareForGetHello
    handleRequest() {
        this.ok({
            hello: 'world'
        })
    }
}
const route = Route.get('/hello', new GetHelloController());

Notice how the three middleware functions are different:

  • One is async, another is a normal one, but the other one does not have the next function parameter used, but this is still okay because Expressive calls it internally
  • These cases are handled by Expressive internally and allows you to declare middleware in a flexible way

Request validation using Celebrate

Expressive uses celebrate for API endpoint validations. A schema can be added to any endpoint using the 'validationSchema' class property of a controller.

const { Route, Joi, BaseController } = require('@siddiqus/expressive');

class GetUserByIdController extends BaseController {
    validationSchema = {
      params: {
        userId: Joi.number().required()
      },
      body: {}, // keys with Joi schema
      query: {},
      headers: {} // and others based on celebrate's documentation
    }

    handleRequest() {
        this.ok({
            some: 'user'
        })
    }
}

const getUserById = Route.get('/users/:userId', new GetUserByIdController());

Centralized authorization

You can define an authorizer property at the app, subroute or route level (in case of multiple definitions, they will be executed in that order respectively). Here are the examples:

class SomeController extends BaseController {
    authorizer = (req, res) => {} // authorizer function for this particular route
    // handleRequest is implemented, assume
}

const expressiveRouter = {
  routes: [
    Route.get("/users", new SomeController()),
  ],
  subroutes: [
    {
      path: '/products',
      router: productRouter, // some other defined Expressive router
      authorizer: (req, res) => {} // authorizer function for all routes under /products/*
    }
  ]
}
const app = new ExpressApp(expressiveRouter, {
  authorizer: (req, res, next) => { // authorizer function for the whole app
})

While defining a function at every level gives you granular control over your endpoint authorization, Expressive gives you another way: authorizer objects

Objective authorization (with authorizer objects)

This implementation can be summarized as:

For an endpoint [x], there is a criteria [y] that describes who is authorized to access the endpoint.

You can use this authorization mechanism by defining an authObjectHandler function as a parameter in ExpressApp, with any authorizer property at any level being defined as an object, a string, or an array of those. Defining an authorizer property without declaring the authObjectHandler will throw an error while initializing the app. Here is an example.

  1. Let's say we define an endpoint with an authorizer
class SomeController extends BaseController {
    authorizer = {
        permissions: 'some-permission-criteria'
    }
}
const expressiveRouter = {
  routes: [
    Route.get('/hello', new SomeController())
  ]
};
  1. And we have declared our authObjectHandler in ExpressApp params
import { Handler } from '@siddiqus/expressive';

export const authObjectHandler: Handler = (req, res, next) => {
    const user = req.user; // this object is allowed for any user data
    if (!user) {
        return res.json(403).json({ message: 'unauthenticated' });
    }

    const authorizer = req.authorizer; // req.authorizer is a flattened array of all authorizer objects
    // in our case, req.authorizer = [{ some: 'permission-criteria' }]
    // some logic to authorize the user

    const requiredPermissions = new Set<string>();
    if (Array.isArray(authorizer)) {
        authorizer.forEach((a) => requiredPermissions.add(a));
    } else {
        requiredPermissions.add(authorizer);
    }

    const hasPermissions = user.permissions.some((p) =>
        requiredPermissions.has(p),
    );

    if (!hasPermissions) {
        return res.status(401).json({
            message: 'unauthorized',
        });
    }

    return next();
};


const app = new ExpressApp(expressiveRouter, {
  authObjectHandler,
});

If the authorizer object is declared at any level (app, subroute, or route), the authorizer object (or string) will be appended to a flattened array in req.authorizer.

So by declaring the authObjectHandler in a generic way, we can centrally manage authorization for the whole application at any level by simply defining the authorization criteria in the authorizer object.

Documentation with Swagger

Auto-generated documentation

Firstly, Expressive auto generates Swagger documentation from the declared routes, even if you do not provide any documentation of your own. Currently:

  • For any project, if you declare basic routes, then the swagger will at least show you the routes that are available on the server.
  • If you declare a request validation schema with celebrate syntax, then Swagger parameter definitions will also be auto-generated.

Swagger UI is accessible on the url /docs, and it requires basic authentication. The default value for both user and password is admin.

To set your own username and password, set the environment variables EXPRESS_SWAGGER_USER and EXPRESS_SWAGGER_PASSWORD respectively.

Swagger options

There are a few things you can configure for Swagger through the ExpressApp options parameter.

You can initialize your app with the basic swagger 'info' property as shown below:

const { ExpressApp } = require('@siddiqus/expressive');

const swaggerInfo = {
  version: '1.0.0',
  title: 'Example Expressive App',
  contact: {
    name: 'Sabbir Siddiqui',
    email: '[email protected]'
  }
};

const app = new ExpressApp(router, {
  swaggerInfo: swaggerInfo
});

You can configure whether to only show Swagger UI in development mode, or otherwise

const app = new ExpressApp(router, {
  showSwaggerOnlyInDev: false // default value is true, set to false to enable swagger for non-development environments
});

You can add API authentication using OpenAPI 2.0 specification. For example:

const app = new ExpressApp(router, {
  swaggerSecurityDefinitions: {
    authHeader: {
      type: 'apiKey',
      name: 'Authorization',
      in: 'header'
    }
  }
});

This will add Authorize option in Swagger UI to add an Authorization header value.

Declaring docs manually

Each API endpoint can be documented using Swagger syntax, simply by adding a 'doc' class property to the controller class. Example:

import getHelloDoc from './getHelloDoc'; // Swagger doc format for an endpoint, js or json

class GetHelloController extends BaseController {
    doc = getHelloDoc // Swagger doc format for an endpoint
    // assume handleRequest is implemented here
}

const getUserById = Route.get('/hello', new GetHelloController());

The 'getHelloDoc' JS or JSON could be an Open API 2.x specification JSON, for example:

{
    "tags": [
        "Hello"
    ],
    "description": "Say hello.",
    "responses": {
        "200": {
            "description": "Say hello.",
            "schema": {
                "type": "object",
                "properties": {
                    "hello": {
                        "type": "string",
                        "example": "world"
                    }
                }
            }
        }
    }
}

Writing Swagger specs to a JSON file

To create a swagger.json file, the function writeSwaggerJson can be used from the SwaggerUtils export. Example:

const { SwaggerUtils } = require('expressive');
...
SwaggerUtils.writeSwaggerJson({
  router, // expressive router configuration
  output, // absolute path of output file
  basePath, // api base path
  swaggerInfo, // basic Swagger info
  swaggerSecurityDefinitions // security definitions as per OpenAPI 2 specification
});

File upload

The recommended middleware for file uploads is multer. Currently Typescript support is available for req.file and req.files but you can declare your own req type if you need.

Here's an example using multer, with schema validation:

import { Route, Joi } from '@siddiqus/expressive';
import multer from 'multer';

const uploadFile = multer();

class FileUploadController extends BaseController {
  validationSchema = {
    fileUpload: {
      file: Joi.any().required() // use Joi.any() for any validations
    }
  }
  
  middleware = [uploadFile.single('file')], // adding multer middleware
  
  handleRequest (req, res) {
    const file = req.file;
    const filename = file.originalname;
    const content = file.buffer.toString();
    this.ok({
      filename,
      content  
    })
  }
};

const fileUploadRoute = Route.put('/file-upload', new FileUploadController());

This provides two benefits:

  1. Celebrate error handling with validate the form data according to the schema
  2. Generates swagger doc for file upload

*** Current limitation is the fileUpload in validationSchema is limited to file and files, which means the formData property has to be either file or files for this to work. You can use multer's other methods like fields, but in that case, you won't be able to name the field anything other than file or files.

Examples

  • See the 'example' folder in this repo for the Typescript sample project structure with example controllers and configs.
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