express-joi-model

A middleware for validating express inputs using Joi schemas using classes. Features include:

• Classes for validating input and output
• Replaces the incoming req.body, req.query, etc and with the validated result object with specified class
• Retains the original req.body inside a new property named req.original-body.

Install

You need to install joi with this module since it relies on it in peerDependencies.

npm i express-joi-model joi --save

Example

A JavaScript example can be found in the example/ folder of this repository.

Usage (JavaScript)

const express = require('express')
const { BaseModel, putValidationMiddleware } = require('express-joi-model')
const Joi = require('joi')

const app = express()

class RequestModel extends BaseModel {
    static get __schema() {
        return {
            a: Joi.number(),
            b: Joi.string()
        }
    }
}

app.use(express.json())

app.post('/', putValidationMiddleware({ body: RequestModel }), function (req, res) {
    console.log(req.body)
    return res.json({ res: true })
})

app.listen(8080)

API

The library exports 3 variables - ValidationError, BaseModel, putValidationMiddleware.

1. ValidationError - the error thrown when validation of the object fails
2. BaseModel - the base class to inherit from when making your own model.
3. putValidationMiddleware - the function to generate the middleware using a config.

ValidationError

class ValidationError extends Error

It contains the error string

BaseModel

class BaseModel extends Object

The BaseModel class is to be used to create your own models. The class must have a static __schema property that must be overriden and must return an Object contains the appropriate keys and apt Joi values. Eg:

class RequestModel extends BaseModel {
    static get __schema() {
        return {
            res: Joi.boolean(),
        }
    }
}
const resObj = RequestModel({res: true}) // VALID
const resObj2 = RequestModel({res: "123"}) // INVALID: throws ValidationError

This ensures that the object passed to RequestModel class will follow the schema.

putValidationMiddleware

function putValidationMiddleware(cfg): function baseModelValidation(req, res, next)

Config can only have 4 keys that define what part of request has to be validated. The values have to be classes inherited from BaseModel:

1. body -> validates req.body and stores the validated object in req.body and the original body in req.original_body
2. query -> validates req.query and stores the validated object in req.query and the original body in req.query
3. params -> validates req.params and stores the validated object in req.params and the original body in req.original_params
4. response -> validates the response post return. The response has to be a json object. Returns 500 if response schema doesn't validate. The input validations return 400 if the input isn't valid.

Eg:

app.post('/correct', putValidationMiddleware({ body: RequestModel, response: ResponseModel }), function (req, res) {
    console.log(req.body)
    return res.json({ res: true })
})

Future TODO

• Better error handling + modification capabilities
• Better configurabilty for Joi in request and response