express-joi-validation

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

• TypeScript support.
• Specify the order in which request inputs are validated.
• Replaces the incoming req.body, req.query, etc and with the validated result
• Retains the original req.body inside a new property named req.originalBody. . The same applies for headers, query, and params using the original prefix, e.g req.originalQuery
• Chooses sensible default Joi options for headers, params, query, and body.
• Uses peerDependencies to get a Joi instance of your choosing instead of using a fixed version.

Quick Links

• API
• Usage (JavaScript)
• Usage (TypeScript)
• Behaviours
  • Joi Versioning
  • Validation Ordering
  • Error Handling
  • Joi Options
  • Custom Express Error Handler

Install

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

npm i express-joi-validation joi --save

Example

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

Usage (JavaScript)

const Joi = require('joi')
const app = require('express')()
const validator = require('express-joi-validation').createValidator({})

const querySchema = Joi.object({
  name: Joi.string().required()
})

app.get('/orders', validator.query(querySchema), (req, res) => {
  // If we're in here then the query was valid!  
  res.end(`Hello ${req.query.name}!`)
})

Usage (TypeScript)

For TypeScript a helper ValidatedRequest and ValidatedRequestWithRawInputsAndFields type is provided. This extends the express.Request type and allows you to pass a schema using generics to ensure type safety in your handler function.

import * as Joi from 'joi'
import * as express from 'express'
import {
  ContainerTypes,
  // Use this as a replacement for express.Request
  ValidatedRequest,
  // Extend from this to define a valid schema type/interface
  ValidatedRequestSchema,
  // Creates a validator that generates middlewares
  createValidator
} from 'express-joi-validation'

const app = express()
const validator = createValidator()

const querySchema = Joi.object({
  name: Joi.string().required()
})

interface HelloRequestSchema extends ValidatedRequestSchema {
  [ContainerTypes.Query]: {
    name: string
  }
}

app.get(
  '/hello',
  validator.query(querySchema),
  (req: ValidatedRequest<HelloRequestSchema>, res) => {
    // Woohoo, type safety and intellisense for req.query!
    res.end(`Hello ${req.query.name}!`)
  }
)

You can minimise some duplication by using joi-extract-type.

NOTE: this does not work with Joi v16+ at the moment. See this issue.

import * as Joi from 'joi'
import * as express from 'express'
import {
  // Use this as a replacement for express.Request
  ValidatedRequest,
  // Extend from this to define a valid schema type/interface
  ValidatedRequestSchema,
  // Creates a validator that generates middlewares
  createValidator
} from 'express-joi-validation'

// This is optional, but without it you need to manually generate
// a type or interface for ValidatedRequestSchema members
import 'joi-extract-type'

const app = express()
const validator = createValidator()

const querySchema = Joi.object({
  name: Joi.string().required()
})

interface HelloRequestSchema extends ValidatedRequestSchema {
  [ContainerTypes.Query]: Joi.extractType<typeof querySchema>

  // Without Joi.extractType you would do this:
  // query: {
  //   name: string
  // }
}

app.get(
  '/hello',
  validator.query(querySchema),
  (req: ValidatedRequest<HelloRequestSchema>, res) => {
    // Woohoo, type safety and intellisense for req.query!
    res.end(`Hello ${req.query.name}!`)
  }
)

API

Structure

• module (express-joi-validation)
  • createValidator(config)
    • query(options)
    • body(options)
    • headers(options)
    • params(options)
    • response(options)
    • fields(options)

createValidator(config)

Creates a validator. Supports the following options:

• passError (default: false) - Passes validation errors to the express error hander using next(err) when true
• statusCode (default: 400) - The status code used when validation fails and passError is false.

validator.query(schema, [options])

Creates a middleware instance that will validate the req.query for an incoming request. Can be passed options that override the config passed when the validator was created.

Supported options are:

• joi - Custom options to pass to Joi.validate.
• passError - Same as above.
• statusCode - Same as above.

validator.body(schema, [options])

Creates a middleware instance that will validate the req.body for an incoming request. Can be passed options that override the options passed when the validator was created.

Supported options are the same as validator.query.

validator.headers(schema, [options])

Creates a middleware instance that will validate the req.headers for an incoming request. Can be passed options that override the options passed when the validator was created.

Supported options are the same as validator.query.

validator.params(schema, [options])

Creates a middleware instance that will validate the req.params for an incoming request. Can be passed options that override the options passed when the validator was created.

Supported options are the same as validator.query.

validator.response(schema, [options])

Creates a middleware instance that will validate the outgoing response. Can be passed options that override the options passed when the instance was created.

Supported options are the same as validator.query.

validator.fields(schema, [options])

Creates a middleware instance that will validate the fields for an incoming request. This is designed for use with express-formidable. Can be passed options that override the options passed when the validator was created.

The instance.params middleware is a little different to the others. It must be attached directly to the route it is related to. Here's a sample:

const schema = Joi.object({
  id: Joi.number().integer().required()
});

// INCORRECT
app.use(validator.params(schema));
app.get('/orders/:id', (req, res, next) => {
  // The "id" parameter will NOT have been validated here!
});

// CORRECT
app.get('/orders/:id', validator.params(schema), (req, res, next) => {
  // This WILL have a validated "id"
})

Supported options are the same as validator.query.

Behaviours

Joi Versioning

This module uses peerDependencies for the Joi version being used. This means whatever joi version is in the dependencies of your package.json will be used by this module.

Validation Ordering

Validation can be performed in a specific order using standard express middleware behaviour. Pass the middleware in the desired order.

Here's an example where the order is headers, body, query:

route.get(
  '/tickets',
  validator.headers(headerSchema),
  validator.body(bodySchema),
  validator.query(querySchema),
  routeHandler
);

Error Handling

When validation fails, this module will default to returning a HTTP 400 with the Joi validation error as a text/plain response type.

A passError option is supported to override this behaviour. This option forces the middleware to pass the error to the express error handler using the standard next function behaviour.

See the Custom Express Error Handler section for an example.

Joi Options

It is possible to pass specific Joi options to each validator like so:

route.get(
  '/tickets',
  validator.headers(
    headerSchema,
    {
      joi: {convert: true, allowUnknown: true}
    }
  ),
  validator.body(
    bodySchema,
    {
      joi: {convert: true, allowUnknown: false}
    }
  )
  routeHandler
);

The following sensible defaults for Joi are applied if none are passed:

Query

• convert: true
• allowUnknown: false
• abortEarly: false

Body

• convert: true
• allowUnknown: false
• abortEarly: false

Headers

• convert: true
• allowUnknown: true
• stripUnknown: false
• abortEarly: false

Route Params

• convert: true
• allowUnknown: false
• abortEarly: false

Fields (with express-formidable)

• convert: true
• allowUnknown: false
• abortEarly: false

Custom Express Error Handler

const validator = require('express-joi-validation').createValidator({
  // This options forces validation to pass any errors the express
  // error handler instead of generating a 400 error
  passError: true
});

const app = require('express')();
const orders = require('lib/orders');

app.get('/orders', validator.query(require('./query-schema')), (req, res, next) => {
  // if we're in here then the query was valid!
  orders.getForQuery(req.query)
    .then((listOfOrders) => res.json(listOfOrders))
    .catch(next);
});

// After your routes add a standard express error handler. This will be passed the Joi
// error, plus an extra "type" field so we can tell what type of validation failed
app.use((err, req, res, next) => {
  if (err && err.error && err.error.isJoi) {
    // we had a joi error, let's return a custom 400 json response
    res.status(400).json({
      type: err.type, // will be "query" here, but could be "headers", "body", or "params"
      message: err.error.toString()
    });
  } else {
    // pass on to another error handler
    next(err);
  }
});

In TypeScript environments err.type can be verified against the exported ContainerTypes:

import { ContainerTypes } from 'express-joi-validation'

app.use((err: any|ExpressJoiError, req: express.Request, res: express.Response, next: express.NextFunction) => {
  // ContainerTypes is an enum exported by this module. It contains strings
  // such as "body", "headers", "query"...
  if (err && err.type in ContainerTypes) {
    const e: ExpressJoiError = err
    // e.g "you submitted a bad query paramater"
    res.status(400).end(`You submitted a bad ${e.type} paramater`)
  } else {
    res.status(500).end('internal server error')
  }
})