# ๐ฆ express-openapi-validator
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**An OpenApi validator for ExpressJS** that automatically validates **API** _**requests**_ and _**responses**_ using an **OpenAPI 3** specification.
[๐ฆexpress-openapi-validator](https://github.com/cdimascio/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](#example-express-api-server).
**Features:**
- โ๏ธ request validation
- โ๏ธ response validation (json only)
- ๐ฎ security validation / custom security functions
- ๐ฝ 3rd party / custom formats / custom data serialization-deserialization
- ๐งต optionally auto-map OpenAPI endpoints to Express handler functions
- โ๏ธ **\$ref** support; split specs over multiple files
- ๐ file upload
**Docs:**
- ๐ [documenation](https://github.com/cdimascio/express-openapi-validator/wiki)
[](https://GitHub.com/cdimascio/express-openapi-validator/stargazers/) [](https://twitter.com/intent/tweet?text=Check%20out%20express-openapi-validator%20by%20%40CarmineDiMascio%20https%3A%2F%2Fgithub.com%2Fcdimascio%2Fexpress-openapi-validator%20%F0%9F%91%8D)
[NestJS](https://github.com/cdimascio/express-openapi-validator/tree/master/examples/9-nestjs)
[Koa](https://github.com/cdimascio/express-openapi-validator/tree/lerna-fastify/packages/koa-openapi-validator) and [Fastify](https://github.com/cdimascio/express-openapi-validator/tree/lerna-fastify/packages/fastify-openapi-validator) now available! ๐
## Install
```shell
npm install express-openapi-validator
## latest beta
npm install express-openapi-validator@4.14.0-beta.1
```
## Usage
1. Require/import the openapi validator
```javascript
const OpenApiValidator = require('express-openapi-validator');
```
or
```javascript
import * as OpenApiValidator from 'express-openapi-validator';
```
2. Install the middleware
```javascript
app.use(
OpenApiValidator.middleware({
apiSpec: './openapi.yaml',
validateRequests: true, // (default)
validateResponses: true, // false by default
}),
);
```
3. Register an error handler
```javascript
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](#example-express-api-server)_.
## [Documentation](https://github.com/cdimascio/express-openapi-validator/wiki)
See the [wiki](https://github.com/cdimascio/express-openapi-validator/wiki) for complete documenation
## License
[MIT](LICENSE)
