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3.2.3 • Public • Published

Hydra Promoted

npm version

This package wraps hydra express and it's all built in typescript it offers hydra and hydra express interfaces , controllers , middlewares and dependency injection capabilities

Installation and Prerequisites

First install it by this command

 npm i hydra-promoted

Dependency injection

also to be able to use dependency injection you will need to install inversify

 npm i inversify

After that please install this library for decorators dependency injection

npm i reflect-metadata

then don't forget to import it in your app.ts (assuming you are in a typescript project).

import  'reflect-metadata';

Tsconfig changes

Now make sure in your tsconfig.json you have enabled the decorators , emitted their metadata and added reflect-metadata to the types field

"experimentalDecorators":  true,
"emitDecoratorMetadata":  true,
"types":  ["reflect-metadata"],


Controllers and Middlewares

using hydra-promoted allows you to have controllers in express so , for example if your code is inside directory called src

create a folder called controllers and another folder called middlewares inside it. then assuming you are in a typescript project add those lines to your app.ts

In this version we have renewed how you can initialize the controllers and middlewares to prevent dynamic imports since it makes some problems if you are using something like webpack for example

so here is the new way to initialize the controllers and middlewares

import { Controllers , Middlewares } from 'hydra-promoted';
import { AuthMiddleware } from './middlewares';
import { ExampleController } from './controllers';

// use it like that
    { instance: ExampleController , name: 'TestController' }

    { instance: AuthMiddleware , name: 'TestMiddleware' }

the above lines registers your controllers and middlewares that are in those arrays so , they can be used later using the Routers.

IMPORTANT NOTE When putting the controller instance like that this will be it's name to be used in making the routers to them .

and note here this is another way to change the instance name if there are two middlewares with the same name you can use this way to change a middlewares name. by specifying the instance and the instance name to be used with in the Routers { instance: AuthMiddleware , name: 'TestMiddleware' }

also it's usually recommended to put the above controller and middleware providers in separate config files for example ControllerRegistery.ts and MiddlewaresRegistery.ts

Example controller

NOTE do not forget to register the controller in the controllers provider as explained above

A Controller should look like that for the provider to be able to use it.

import { injectable } from 'inversify';
import { AppRequest, AppResponse } from 'hydra-promoted';

export  class  ExampleController  {
    index(req:  AppRequest,  res:  AppResponse)  {
        // your code here

now how will you route to that controller open the file where your routes exist for example the index.ts file

Routing to controllers

this is how to use that controller

import { Router } from 'hydra-promoted';

// this will register the '/' to go to the example controller and run // the index function.
Router.get('/', 'ExampleController@index');

module.exports  =  Router.getRouter();

Example middleware

middlewares should look like that

import { injectable } from 'inversify';
import { AppRequest, AppResponse } from 'hydra-promoted';

export class TestMiddleware {
    handle(req:  AppRequest,  res:  AppResponse,  next:  Function)  {
        console.log('Hello world Middleware');
        return  next();

Using middlewares

NOTE don't forget to register your middleware using the middleware provider mentioned in the first section.

middlewares are used like that

import { Router } from 'hydra-promoted';

// this will register the '/' to go to the example controller and run // the index function.
Router.get('/', 'TestMiddleware','ExampleController@index');

module.exports  =  Router.getRouter();

Dependency injection

As you have noticed above there were some decorators above the controllers those helps the dependency injection DI inside hydra-promoted to make instances from those controllers and middlewares.

we will now see how to make services and inject them. you should also know that we are using inversify js to make all this possible.

Also you may refer to inversify docs if you have any difficulties understanding.

Example Service

First we will start making an example service

import { injectable } from 'inversify';

export  class  ExampleService  {
    testMe()  {
        console.log('Hello world is an Example service');

Register service in the DI container

now you should register the services in the bindings array create a file called DIManager.ts which will look like that

import { DIManager } from 'hydra-promoted';
import { ExampleService } from '../serviceProviders/ExampleService';


as you can notice we have imported the DIManager from the hydra-promoted which will put that service in the bindings container for inversify js.

How to inject the service in your controller or any other service

now you want to inject and use your service this is how you can do it in your controller also NOTE that any class with the @injectable can inject any service as long as it is registered in the DI container as in the above snippet.

import { injectable } from 'inversify';
import { AppRequest, AppResponse } from 'hydra-promoted';
import { ExampleService } from '../serviceProviders/ExampleService';

export  class  ExampleController  {
    // NOTICE here how we injected our service
    constructor(public  testService:  ExampleService)  {}

    index(req:  AppRequest,  res:  AppResponse)  {
        return  res.sendOk({
                hello:  'world'

as easy as that your service instance exists with you in the controller also a service can also be injected in another service.

Making API requests

This section will explain how to make api requests to other hydra services since hydra provide load balancing if we have multiple services of the same service.

we have two methods for making api requests


This method is the normal way of requesting we just give it a UMF message and then it will send the request

you can check the UMF message format docs here.


import { HydraApiRequest } from 'hydra-promoted';

let result = await HydraApiRequest({
    body:  { message: 'some data'},

and the response will just be a json object that looks like that

    headers:  { // response headers here},
    result:  { // response body },
    statusCode:  200, 
    statusDescription:  '',
    statusMessage:  'Ok'

NOTE: this is the response standard shape so , you will always receive something like the above json in any response from a hydra service


This is the second method which provides secure encrypted requests between the hydra services using the Rsa encryption.


it's usage is exactly similar to the above method but with additional required field which is the public key of the service you are going to call.

let  result  =  await  HydraSecureApiRequest({
    body:  { message : 'some data' },
    to:  'serviceName:[method]/path/to/router',
    publicKey:  './public.pem'

as you can see it is the same with the additional field the public key

responses from the HydraSecureApiRequest will be exactly the same as the above method as it will handle any decryption needed to be done on the responses.

Handling Hydra Secure request from the receiver side

Now you should be asking what if I am the receiver of the request should I handle everything myself in that case we are exposing a middleware which handles all the decryption logic for you as a receiver for the Rsa encrypted request

middleware is called HandleRsaRequest


this is a normal express middleware which can be used like that

import { HandleRsaRequest } from 'hydra-promoted';


as you can see it just requires the private key path or object which will handle all the decryption of the request needed for you and you will then receive a normal request as usual.

Example private key with passphrase

Sometimes the private key will have a passphrase so , in such a case the private key property will accept an object instead of a string

import { HandleRsaRequest } from 'hydra-promoted';

        path: './private.pem',
        passphrase: 'supersecretpassphrase'

also this is how you can use in the middleware that we provide

import { HandleRsaRequest, Middleware, AppRequest, AppResponse } from 'hydra-promoted';
import { injectable } from 'inversify';

export class HandleRsa implements Middleware {
    handle(req: AppRequest, res: AppResponse, next: Function) {
        return HandleRsaRequest('./private.pem')(req, res, next);

we are just calling the HandleRsaRequest which will return a middleware and we are just passing it the req , res and next that it needs it.

How the Receiver will respond an encrpyted response

the sender will be waiting for encrypted response too from the receiver so, we need to have a method too to encrypt the receiver response.

import { injectable } from 'inversify';
import { AppRequest, AppResponse, SendSecure } from 'hydra-promoted';

class ExampleController{

    securedFunction(req: AppRequest, res: AppResponse) {
        return SendSecure({
            body: "This response string will be encrypted",
                path: './privateKey.pem',
                passphrase: '123'
            res: res


as the example above this SendSecure function will handle all the encryption logic for you it just encrypts the response using the private key and the other requesting service will just use the receiving side public key to decrypt it.

Encryption helpers

hydra promoted also provide some helpers for encryption and decryption which ease out the Rsa encryption and decrpytion steps.

Rsa Encryption using private key

import { RsaEncryptWithPrivate } from 'hydra-promoted';

let encryptedString = await RsaEncryptWithPrivate("string you want to decrypt","./privatekey/path.pem");


let encryptedString = await RsaEncryptWithPrivate("string you want to decrypt",{
    path: "./privatekey/path.pem",
    passphrase: process.env.PASS_PHRASE

the return result is the encrypted is a promise which resolves to your encrpyted string in a base64 string format

Rsa Decryption using public key

import { RsaDecryptWithPublic } from 'hydra-promoted';

let yourString = await RsaDecryptWithPublic(encryptedString,"./publickey/path.pem");

the rsa decrypt just need your encrypted string and the public key path to decrypt

NOTE of course the the public key should be the other key pair for the encryption private key.

Some Important Helpers

Now if you were wondering where is the hydra part in this there you go hydra-promoted exposes the following variables which will let you use Hydra and hydra express with intellisense.


import { HydraExpress } from 'hydra-promoted';

This is the hydra express instance .


import { Hydra } from 'hydra-promoted';

This is the Hydra instance itself.


import { ServerResponse } from 'hydra-promoted'; This is a hydra utility for adding service responses.


import { ExpressInstance as Express } from 'hydra-promoted';

This is the express instance which is used inside hydra.

Release Notes


added feature that you can now not only send string handlers that target controllers now you can also put functions instead of strings exactly as express


    Router.get('/path',(req,res) => res.send('I can work with that'));


bug fix where the middleware handle functions were losing context of the middleware class

3.1.2 , 3.1.3

bug fix where the controller function error handler catch was not running in the case of a promise function controller now all controller functions are automatically handled


  • bug fix where HydraApiRequest was not working correctly from the controllers
  • adding a new function for sending an encrypted response back from an encrypted request
  • hydra does not accept string as body but this is handled inside the hydraMakeRequest function by including that string inside an object with a message as key and the string as the value.
  • fixed a bug where encryped and decrypted body were not parsed and they stayed on their string forms


exposed the Rsa encrypt private and decrypt using public functions


npm i hydra-promoted

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