Express Joi Validators (EJV)

Introduction

This is a Joi validation wrapper middleware for validating express request headers and body. All data validated by express-joi-validators is passed to a context object 'ctx' which is set on the request object of express.

1. Getting Started

Here we will show you how to get started with express-joi-validators, through an example. Please follow the steps below to guide you through the process:

• create a new folder on your desktop
• navigate into the folder with your CLI. $ cd your_directory_path
• create a file called index.js
• copy and paste the example code into your index.js file
• run npm init -y
• run npm i express @hapi/joi express-joi-validators
• run node index.js
• open http://localhost:5000 in your browser
• you should now get a response similar to the one given in the example below.

Note: If your version of express is lower than 4.16.0 you will have to install the body-parser package and modify part 3 of the example accordingly.

// PART 1: Setting up express
const express = require('express') 
const app = express()
const server = require('http').createServer(app)
const port = 5000

// PART 2: Require in Joi and express-joi-validators
const Joi = require('@hapi/joi')
const { validateHeader, validateBody } = require('express-joi-validators')

// PART 3: Setting up request JSON and URL parsers. Note: if they are not called, joi will not call next(error)
app.use(express.json()) // This middleware is required for schemas validation to work.
app.use(express.urlencoded({ extended: true }))

// PART 4: Create Joi schema for validating request body
const schema = Joi.object().options({abortEarly: false}).keys({
    username: Joi.string().lowercase().required(),
    password: Joi.string().min(6).required(),
})

// PART 5: Create route with validatorBody mounted
const requestHandler = (req, res) => res.end()
app.use('/', validateBody(schema), requestHandler)


// PART 6: Mount an express errorHandler middleware to catch and handle the Joi validation Error
const errorHandler = (err, req, res, next) => res.status(422).json(err)
app.use(errorHandler) 

// PART 7: Set server to listen for requests
server.listen(port, () => {
    console.log(`server running at http://localhost:${port}`)
})

The code above would yield the response below:

{
    "_original": {},
    "details": [
        {
            "message": "\"username\" is required",
            "path": [
                "username"
            ],
            "type": "any.required",
            "context": {
                "label": "username",
                "key": "username"
            }
        },
        {
            "message": "\"password\" is required",
            "path": [
                "password"
            ],
            "type": "any.required",
            "context": {
                "label": "password",
                "key": "password"
            }
        }
    ]
}

2. Getting the Validated Response Body

If the request passes all validation rules, you access the validated body in your route through req.ctx.body.

example:

app.use('/login', validateBody(loginShema), (req, res) => {
    const { body } = req.ctx
    // your code ...
})

3. Getting the Validated Response Header

If the request passes all validation rules, you access the validated header in your route through req.ctx.header.

example:

app.use('/login', validateBody(loginShema), (req, res) => {
    const { header } = req.ctx
    // your code ...
})