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Event validation middleware for Middy
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Event Validation Middleware for Middy

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Joi powered event validation middleware for Middy.

The middleware integrates Joi validation library to validate AWS Lambda events triggered by API Gateway.

Failed validations throw error of http-errors instance with status code 422.


import middy from 'middy';
import eventValidator from '@keboola/middy-event-validator';

export const handler = middy(() => {
  // ...

    path: {
      id: Joi.string().required()
    body: {
      size: Joi.number().integer()
    pagination: true

The configuration accepts following options:

  • headers - validation of HTTP headers
  • body - validation of HTTP body in JSON format
  • path - validation of path parameters (shortcut for API Gateway's pathParameters)
  • query - validation of query string (shortcut for API Gateway's queryStringParameters)
  • pagination: true - shortcut for two query string parameters offset and limit validated as numbers.
    • Default and maximum for limit is 1000. It can be changed by a definition: pagination: { max: 10 }

The module also offers a set of validation shortcuts using class Validation:

import middy from 'middy';
import eventValidator, { Validation } from '@keboola/middy-event-validator';

    path: {
      id: Validation.string('id').required()

List of available shortcuts:

  • getJoi() - returns Joi instance for custom validation
  • forbidden(param) - setting of the parameter is forbidden
  • boolean(param) - boolean value
  • string(param) - string. All string shortcuts promote trimming of trailing white spaces
  • stringMaxLength(param, length) - string with maximal length
  • integer(param)
  • object(param)
  • enum(param, values)
  • array(param)
  • arrayOfStrings(param)

All shortcuts create optional parameters, for required parameters add .required().

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