Fastify
## Middleware
From Fastify v3, middleware support does not come out of the box with the framework itself, but it's offered as an external plugin via [`fastify-express`](https://github.com/fastify/fastify-express) and [`middie`](https://github.com/fastify/middie).
If you need to use an express style middleware you can use one of the two plugins above:
```js
await fastify.register(require('fastify-express'))
fastify.use(require('cors')())
fastify.use(require('dns-prefetch-control')())
fastify.use(require('frameguard')())
fastify.use(require('hsts')())
fastify.use(require('ienoopen')())
fastify.use(require('x-xss-protection')())
```
You can also use [`middie`](https://github.com/fastify/middie), which provides support for simple Express-style middlewares but with improved performances:
```js
await fastify.register(require('middie'))
fastify.use(require('cors')())
```
Remember that middleware can be encapsulated, this means that you can decide where your middleware should run by using `register` as explained in the [plugins guide](./Plugins-Guide.md).
Fastify middleware also do not expose the `send` method or other methods specific to the Fastify [Reply](./Reply.md#reply) instance. This is because Fastify wraps the incoming `req` and `res` Node instances using the [Request](./Request.md#request) and [Reply](./Reply.md#reply) objects internally, but this is done after the middleware phase. If you need to create middleware, you have to use the Node `req` and `res` instances. Otherwise, you can use the `preHandler` hook which already has the [Request](./Request.md#request) and [Reply](./Reply.md#reply) Fastify instances. For more information, see [Hooks](./Hooks.md#hooks).
#### Restrict middleware execution to a certain path(s)
If you need to run a middleware only under certain path(s), just pass the path as first parameter to `use` and you are done!
*Note that this does not support routes with parameters, (eg: `/user/:id/comments`) and wildcards are not supported in multiple paths.*
```js
const path = require('path')
const serveStatic = require('serve-static')
// Single path
fastify.use('/css', serveStatic(path.join(__dirname, '/assets')))
// Wildcard path
fastify.use('/css/*', serveStatic(path.join(__dirname, '/assets')))
// Multiple paths
fastify.use(['/css', '/js'], serveStatic(path.join(__dirname, '/assets')))
```
### Alternatives
Fastify offers some alternatives to the most commonly used middlewares, such as [`fastify-helmet`](https://github.com/fastify/fastify-helmet) in case of [`helmet`](https://github.com/helmetjs/helmet), [`fastify-cors`](https://github.com/fastify/fastify-cors) for [`cors`](https://github.com/expressjs/cors) and [`fastify-static`](https://github.com/fastify/fastify-static) for [`serve-static`](https://github.com/expressjs/serve-static).