express-openapi-validator

What is express-openapi-validator?

express-openapi-validator is a middleware for Express.js that validates API requests and responses against an OpenAPI 3.0 specification. It helps ensure that your API adheres to the defined contract, improving reliability and maintainability.

What are express-openapi-validator's main functionalities?

Request Validation

This feature validates incoming requests against the OpenAPI specification. If a request does not conform to the spec, an error is returned.

const express = require('express');
const OpenApiValidator = require('express-openapi-validator');
const app = express();

app.use(express.json());

app.use(
  OpenApiValidator.middleware({
    apiSpec: './api.yaml',
    validateRequests: true,
  })
);

app.post('/pets', (req, res) => {
  res.json({ message: 'Pet added successfully' });
});

app.use((err, req, res, next) => {
  res.status(err.status || 500).json({ message: err.message });
});

app.listen(3000, () => console.log('Server running on port 3000'));

Response Validation

This feature validates outgoing responses against the OpenAPI specification. If a response does not conform to the spec, an error is returned.

const express = require('express');
const OpenApiValidator = require('express-openapi-validator');
const app = express();

app.use(express.json());

app.use(
  OpenApiValidator.middleware({
    apiSpec: './api.yaml',
    validateResponses: true,
  })
);

app.get('/pets', (req, res) => {
  res.json([{ id: 1, name: 'Fluffy' }]);
});

app.use((err, req, res, next) => {
  res.status(err.status || 500).json({ message: err.message });
});

app.listen(3000, () => console.log('Server running on port 3000'));

Security Validation

This feature validates security requirements defined in the OpenAPI specification. It ensures that requests meet the necessary security criteria, such as API keys or OAuth tokens.

const express = require('express');
const OpenApiValidator = require('express-openapi-validator');
const app = express();

app.use(express.json());

app.use(
  OpenApiValidator.middleware({
    apiSpec: './api.yaml',
    validateSecurity: true,
  })
);

app.get('/secure-endpoint', (req, res) => {
  res.json({ message: 'Secure data' });
});

app.use((err, req, res, next) => {
  res.status(err.status || 500).json({ message: err.message });
});

app.listen(3000, () => console.log('Server running on port 3000'));

Other packages similar to express-openapi-validator

swagger-express-middleware

swagger-express-middleware is a similar package that provides middleware for Express.js to handle Swagger (OpenAPI) documents. It offers request validation, mock responses, and more. Compared to express-openapi-validator, it is more focused on Swagger 2.0 and provides additional features like mock responses.

openapi-backend

openapi-backend is a framework-agnostic library for building and validating APIs based on OpenAPI specifications. It provides request validation, response validation, and routing. Unlike express-openapi-validator, it is not tied to Express.js and can be used with other frameworks or even standalone.

ajv

ajv (Another JSON Schema Validator) is a JSON schema validator that can be used to validate data against JSON schemas, including OpenAPI schemas. While it is not specifically designed for Express.js or OpenAPI, it can be integrated into an Express.js application for similar validation purposes. It offers high performance and extensive features for JSON schema validation.

README

🦋 express-openapi-validator

An OpenApi validator for ExpressJS that automatically validates API requests and responses using an OpenAPI 3 specification.

🦋express-openapi-validator is an unopinionated library that integrates with new and existing API applications. express-openapi-validator lets you write code the way you want; it does not impose any coding convention or project layout. Simply, install the validator onto your express app, point it to your OpenAPI 3 specification, then define and implement routes the way you prefer. See an example.

Features:

• ✔️ request validation
• ✔️ response validation (json only)
• 👮 security validation / custom security functions
• 👽 3rd party / custom formats / custom data serialization-deserialization
• 🧵 optionally auto-map OpenAPI endpoints to Express handler functions
• ✂️ $ref support; split specs over multiple files
• 🎈 file upload

Docs:

• 📖 documentation

NestJS Koa and Fastify now available! 🚀

OAS 3.1 (experimental)

Install

npm install express-openapi-validator

# experimental OAS 3.1 in alpha (contributions welcome - see branch `oas-3.1` and pr-882 
# please provide feedback on (issue-573)
npm install express-openapi-validator@6.0.0-alpha.3

Usage

1. Require/import the openapi validator

const OpenApiValidator = require('express-openapi-validator');

or

import * as OpenApiValidator from 'express-openapi-validator';

1. Install the middleware

app.use(
  OpenApiValidator.middleware({
    apiSpec: './openapi.yaml',
    validateRequests: true, // (default)
    validateResponses: true, // false by default
  }),
);

1. Register an error handler

app.use((err, req, res, next) => {
  // format error
  res.status(err.status || 500).json({
    message: err.message,
    errors: err.errors,
  });
});

Important: Ensure express is configured with all relevant body parsers. Body parser middleware functions must be specified prior to any validated routes. See an example.

Documentation

See the doc for complete documenation

deprecated legacy doc

License

MIT