Creating a custom ServiceProvider in your Adonis.js project

I recently found Nuxt, and by extension re-discovered a wonderful Node.js framework named Adonis. Since then I've been slowly developing a small project as a learning experience and I would like to share with you something I found to be missing from the Adonis documentation.

When you're using a third-party library such as Firebase in your project, usually you include the module and instantiate the module with configuration values each time you use it or you create a global. Adonis has two features called IoC and ServiceProviders to prevent you from having to do that and a centralized configuration directory to prevent configuration values being hardcoded into your codebase.

The problem is that Adonis doesn't describe where to put your custom services, when to use these features, or how to tell your Adonis application they exist to allow you to use them.

So I'd like to share with you what I've learned about creating a custom ServiceProvider in Adonis.

Creating the ServiceProvider

Service providers are placed within the providers/ directory in your Adonis application. The difference between a Simple Provider and a ServiceProvider is that the Simple Provider doesn't get hoisted onto the Adonis application and it doesn't have access to the Adonis application context object. Simple Providers are also stored in the providers/ directory and ServiceProviders can include them to hoist them onto the Adonis application.

First we create our Simple Provider for Firebase in a file named providers/firebaseService.js:

class FirebaseService {
  constructor (Config) {
    // Include our firebase-admin module
    // Find out more at: https://firebase.google.com/docs/admin/setup
    const FirebaseAdmin = require('firebase-admin')

    // Obtain Firebase configuration from config/services.js
    // Create the file if it doesn't exist and Adonis will pick it up
    const FirebaseConfig = Config.get('services.firebase') 

    // Initialize our priviledged firebase admin application
    FirebaseAdmin.initializeApp({
      credential: FirebaseAdmin.credential.cert({
        projectId: FirebaseConfig.credentials.projectId,
        clientEmail: FirebaseConfig.credentials.clientEmail,
        privateKey: FirebaseConfig.credentials.privateKey
      }),

      databaseURL: FirebaseConfig.databaseURL
    })

    // Return our FirebaseAdmin object
    return FirebaseAdmin
  }
}

module.exports = FirebaseService

Now we need to create our ServiceProvider that consumes our Simple Provider we just created in a new file named providers/firebaseServiceProvider.js:

const ServiceProvider = require('adonis-fold').ServiceProvider
const FirebaseService = require('./firebaseService')

class FirebaseProvider extends ServiceProvider {
  * register () {
    // Register our ServiceProvider on the namespace: Adonis/Services/Firebase
    // Obtain application reference: app
    this.app.bind('Adonis/Services/Firebase', (app) => {
      // Obtain application configuration in config/
      const Config = app.use('Adonis/Src/Config')

      // Export our service
      return new FirebaseService(Config)
    })
  }
}

module.exports = FirebaseProvider

Great, we now have our service provider, how do we tell our Adonis application how to use it?

Create our ServiceProvider definition in our Adonis application

Service definitions are setup in the bootstrap/app.js file on the providers array, you will have to require the path module should it not already be required, and provide a relative path to the ServiceProvider we created in the last step:

const path = require('path')

const providers = [
  // ...
  path.join(__dirname, '..', 'providers', 'firebaseServiceProvider')
  // ...
]

Start using our ServiceProvider

Now inside of our Controllers or Models we can use our Firebase ServiceProvider like so:

const Firebase = use('Adonis/Services/Firebase')

// Retrieve services from Firebase
const FirebaseAuth = Firebase.auth()
const FirebaseDatabase = Firebase.database()

// Initialize a second application
const SecondFirebaseApp = Firebase.initializeApp(/* ... config ... */, "second")

Want to learn more about firebase-admin? Just click that link.

Now you're ready to implement your own custom services, good luck and until next time... Stay safe!

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