swagger-http-router v4.2.1

swagger-http-router

A HTTP router based on your Swagger/OpenAPI definition.

Why write code when you have a Swagger/OpenAPI definition?

By taking part of the Swagger/OpenAPI standard and dependency injection patterns, swagger-http-router provides a convenient, highly modular and easily testable REST tool.

Usage

import { constant } from 'knifecycle';
import initDB from './services/db';
import {
  initWepApplication
} from 'swagger-http-router';

import API from './swagger.api.json';
import * as HANDLERS from './handlers';

run();

async function run() {
  try {
    // STEP 1: Spawn a Knifecycle instance and attach
    // it the API definition and its handlers
    const $ = initWepApplication(API, HANDLERS);

    // STEP 2: Register additional services
    // Override the build in `uniqueId` service
    // with the UUID v4 function
    $.register(constant('uniqueId', uuid.v4))
    // Provide the process environment
    .register(constant('ENV', process.env))
    // Register the database initializer
    .register(initDB);

    // STEP 3: Run your app!
    // Run the execution silo that encapsulates the app
    // Note that the `httpServer` and `process` services
    // are injected for their respective side effects:
    // creating the server and managing the process
    // lifecycle
    const { ENV, log, $destroy } = await $.run(['ENV', 'log', 'httpServer', 'process', '$destroy']);

    log('info', `On air 🚀🌕`);

    if(ENV.DRY_RUN) {
      await $destroy();
    }
  } catch(err) {
    console.error('💀 - Cannot launch the process:', err.stack);
    process.exit(1);
  }
)

In order to work, your Swagger definition endpoints must provide an operationId. This is how the router figures out which handler to run. Those ids have to be unique. Here is a sample Swagger definition you could use as is:

// file: ./my-swagger.json
{
  "host": "localhost:1337",
  "basePath": "/v1",
  "schemes": ["http"],
  // (...)
  "paths": {
    "GET": {
      "/users/{userId}": {
        "operationId": "getUser",
        "summary": "Retrieve a user.",
        "produces": [
          "application/json"
        ],
        "parameters": [{
          "in": "path",
          "name": "userId",
          "type": "number",
          "pattern": "^[0-9]+$"
        }, {
          "in": "query",
          "name": "extended",
          "type": "boolean"
        }, {
          "in": "header",
          "name": "Content-Type",
          "type": "string"
        }],
        "responses": {
          "200": {
            "description": "User found",
            "schema": {
              "type": "object",
              "properties": {
                "id": { "type": "number" },
                "name": { "type": "string" }
              }
            }
          },
          "404": {
            "description": "User not found"
          }
        }
      }
    }
  }
}

To bring to the router the logic that each endpoint implements, you have to create handlers for each operationId:

// file: ./handlers.js

// Knifecycle is the dependency injection tool
// we use. It provides decorators to declare
// which dependencies to inject in your handlers
import { initializer } from 'knifecycle/dist/util';

export default initializer(
  {
    name: 'getUser',
    type: 'service',
    inject: ['db'],
  },
  getUser
);

async function getUser({ db }) {
  return async ({ userId }) => {
    const user = await db.query('users', {
      id: userId,
    });

    return {
      status: 200,
      headers: {},
      body: {
        id: userId,
        name: user.name,
      }
    };
  }
}

As you can see, handlers are just asynchronous functions that takes the request parameters in input and provide a JSON serializable response in output.

This router is designed to be used with a DI system and is particularly useful with knifecycle.

That said, you could completely avoid using a DI system by simply using the initializers as functions and handle their initialization manually. See this alternate example.

Goal

This router is just my way to do things. It is nice if you use it and I'd be happy if you improve it.

To be honest, I think this is a better approach but I do not want to spend energy and fight with giants to make this a standard approach. It means that it will probably never be the next hype and if you use it you must feel confident with forking and maintaining it yourself. That said, the code is well documented and not that hard. Also, the handlers you will end with will be easily reusable in any framework with little to no changes.

You may wonder why I found that I'd better write my own router instead of using current solutions like ExpressJS or HapiJS:

• I want documentation first APIs. No documentation, no web service.
• I want my code to be clear and descriptive instead of binded to some cryptic middleware or plugin defined elsewhere. Here are some thoughts on middlewares that explain this statement in more depth.
• I want easily testable and reusable handlers just returning plain JSON. To be able to reuse it in multiple situations: a lambda/serverless back-end, when rendering server side React views or in my GraphQL server resolvers.
• I prefer functional programming: it just makes my code better. There are too many encapsulated states in existing frameworks. I just want my handlers to be pure and composable. For example, why adding a CORS middleware or plugin when you can just compose handlers?

import { reuseSpecialProps } from 'knifecycle/dist/util';

const CORS = {
  'Access-Control-Allow-Origin': '*',
  'Access-Control-Allow-Methods': 'GET, POST, OPTIONS',
  'Access-Control-Allow-Headers': 'Keep-Alive,User-Agent',
};

export function wrapWithCORS(initHandler) {
  // `reuseSpecialProps` create a new initializer
  // with the original initializer properties
  // applyed on it.
  return reuseSpecialProps(
    initHandler,
    initHandlerWithCORS.bind(null, initHandler)
  );
}

// This function is the actual initializer that
// wraps the handler initializer. It is executed
// once at startup.
async function initHandlerWithCORS(initHandler, services) => {
  const handler = await initHandler(services);

  return handleWithCors.bind(null, handler);
}

// And finally this one applies CORS to the
// response
async function handleWithCors(handler, parameters) {
  const response = await handler(parameters);

  return  {
    ...response,
    headers: {
      ...response.headers,
      ...CORS,
    }
  };
}

• and finally, I want to be able to instrument my code without having to do ugly hacks. This is why DI and Inversion of Control are at the core of my way to handle web services.

You may want to have a look at the architecture notes of this module to better grasp how it is built.

Recommendations

The above usage section shows you a very basic usage of this router. For larger apps:

• you may want to build you Swagger file to avoid repeating yourself. It won't change anything for swagger-http-router since it just assumes a Swagger file.
• you will probably end up by automating the handlers loading with a configuration file. At that point, the DI system will become very handy.
• you will certainly need some more services to make your app work. Please double check if one exists before creating your own. Also, handlers can be reused so feel free to publish yours and add your Swagger path objects to them in order for your users to add them to their own Swagger build.

API

Functions

initErrorHandler(services) ⇒ Promise

Initialize an error handler for the HTTP router

Kind: global function
Returns: Promise - A promise of a function to handle errors

initErrorHandler~errorHandler(transactionId, responseSpec, err) ⇒ Promise

Handle an HTTP transaction error an map it to a serializable response

Kind: inner method of initErrorHandler
Returns: Promise - A promise resolving when the operation completes

initWepApplication(API, HANDLERS, $) ⇒ Knifecycle

Initialize a web application

Kind: global function
Returns: Knifecycle - The passed in Knifecycle instance or the one created by default.

registerHandlers($, HANDLERS) ⇒ void

Register the handlers hash into the given Knifecycle instance

Kind: global function

initHTTPRouter(services) ⇒ Promise

Initialize an HTTP router

Kind: global function
Returns: Promise - A promise of a function to handle HTTP requests.

initHTTPServer(services) ⇒ Promise

Initialize an HTTP server

Kind: global function
Returns: Promise - A promise of an object with a NodeJS HTTP server in its service property.

initHTTPTransaction(services) ⇒ Promise.<function()>

Instantiate the httpTransaction service

Kind: global function
Returns: Promise.<function()> - A promise of the httpTransaction function

Example

import { initHTTPTransaction } from 'swagger-http-router';

const httpTransaction = await initHTTPTransaction({
  log: console.log.bind(console),
  time: Date.now.bind(Date),
});

initHTTPTransaction~httpTransaction(req, res) ⇒ Array

Create a new HTTP transaction

Kind: inner method of initHTTPTransaction
Returns: Array - The normalized request and the HTTP transaction created in an array.

flattenSwagger(API) ⇒ Object

Flatten the inputed Swagger file object

Kind: global function
Returns: Object - The flattened Swagger definition

getSwaggerOperations(API) ⇒ Array

Return a Swagger operation in a more convenient way to iterate onto its operations

Kind: global function
Returns: Array - An array of all the Swagger operations

Example

getSwaggerOperations(API)
.map((operation) => {
   const { path, method, operationId, parameters } = operation;

  // Do something with that operation
});

API

Functions

initErrorHandler(services) ⇒ Promise

Initialize an error handler for the HTTP router

Kind: global function
Returns: Promise - A promise of a function to handle errors

initErrorHandler~errorHandler(transactionId, responseSpec, err) ⇒ Promise

Handle an HTTP transaction error and map it to a serializable response

Kind: inner method of initErrorHandler
Returns: Promise - A promise resolving when the operation completes

initWepApplication(API, HANDLERS, $) ⇒ Knifecycle

Initialize a web application

Kind: global function
Returns: Knifecycle - The passed in Knifecycle instance or the one created by default.

initHTTPRouter(services) ⇒ Promise

Initialize an HTTP router

Kind: global function
Returns: Promise - A promise of a function to handle HTTP requests.

initHTTPServer(services) ⇒ Promise

Initialize an HTTP server

Kind: global function
Returns: Promise - A promise of an object with a NodeJS HTTP server in its service property.

initHTTPTransaction(services) ⇒ Promise.<function()>

Instantiate the httpTransaction service

Kind: global function
Returns: Promise.<function()> - A promise of the httpTransaction function

Example

import { initHTTPTransaction } from 'swagger-http-router';

const httpTransaction = await initHTTPTransaction({
  log: console.log.bind(console),
  time: Date.now.bind(Date),
});

initHTTPTransaction~httpTransaction(req, res) ⇒ Array

Create a new HTTP transaction

Kind: inner method of initHTTPTransaction
Returns: Array - The normalized request and the HTTP transaction created in an array.

flattenSwagger(API) ⇒ Object

Flatten the inputed Swagger file object

Kind: global function
Returns: Object - The flattened Swagger definition

getSwaggerOperations(API) ⇒ Array

Return a Swagger operation in a more convenient way to iterate onto its operations

Kind: global function
Returns: Array - An array of all the Swagger operations

Example

getSwaggerOperations(API)
.map((operation) => {
   const { path, method, operationId, parameters } = operation;

  // Do something with that operation
});

Authors

• Nicolas Froidure

License

MIT