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Middleware

The HTTP middleware are a set of functions executed in sequence, one after the other. The concept of a sequential chain makes it powerful to transform the request or end it at any stage.

Features like sessions, authentication make extensive use of the middleware to add features to the framework.

Middleware can perform one/all of the following operations

  1. Decorate HTTP context and add values to it.

  2. Respond to a given request, without reaching the route action.

  3. Deny requests by throwing errors.

Using Middleware

All of the middleware are registered inside start/kernel.js file and separated into 2 different categories.

Global middleware

The global middleware are executed for each request that has a registered route and defined under the globalMiddleware array.

Middleware are executed in the sequence they are defined. 
const globalMiddleware = [
  'Adonis/Middleware/BodyParser'
]

Named middleware

Named middleware is an object of key/value pairs, and you can define the keys to individual routes or a group of routes to apply certain middleware.

Named middleware are used, when you want to perform certain actions on selected routes only.

const named = {
  auth: 'Adonis/Middleware/Auth'
}

Later you can use the auth key on your Routes.

Route
  .get('users/:id', 'UserController.show')
  .middleware(['auth'])

Also, you can apply multiple middleware to a route, and they are executed in the sequence they are passed.

Middleware Props

To keep middleware configurable at runtime. AdonisJs makes it possible to pass props to named middleware. For example: Using the auth middleware with different authentication scheme for different routes.

Middleware uses the pipe expression to define props. 
Route
  .post('users', 'UsersController.store')
  .middleware(['auth:session'])

And

Route
  .post('posts', 'PostsController.store')
  .middleware(['auth:jwt'])

Multiple props can be passed as auth:session,jwt.

Creating Middleware

You can also create middleware to add application specific logic to the HTTP lifecycle. All project related middleware are stored inside app/Middleware directory.

You can use the adonis command to create a middleware for you.

adonis make:middleware CountryDetector

Output

✔ create  app/Middleware/CountryDetector.js

Creating middleware

Now let’s say we want to use the user ip address and detect their country. We can write all that code inside the handle method of the middleware.

'use strict'

const geoip = use('geoip-lite')

class CountryDetector {
  async handle ({ request }, next) {
    const ip = request.ip()
    request.country = geoip.lookup(ip).country
    await next()
  }
}

module.exports = CountryDetector

Registering middleware

Let’s register this as a global middleware so that we can fetch country for all the users.

start/kernel.js
const globalMiddleware = [
  'App/Middleware/CountryDetector'
]

That is all 😎   Now all of your requests have the country property on it.