HTTP response serializer middleware for the middy framework, the stylish Node.js middleware engine for AWS Lambda
The Http Serializer middleware lets you define serialization mechanisms based on the current content negotiation.
## Install
To install this middleware you can use NPM:
```bash
npm install --save @middy/http-response-serializer
```
## Configuration
The middleware is configured by defining some `serializers`.
```
{
serializers: [
{
regex: /^application\/xml$/,
serializer: ({ body }) => `${body}`,
},
{
regex: /^application\/json$/,
serializer: ({ body }) => JSON.stringify(body)
},
{
regex: /^text\/plain$/,
serializer: ({ body }) => body
}
],
default: 'application/json'
}
```
The `default` (optional) option is used if the request and handler don't specify what type is wanted.
## Serializer Functions
When a matching serializer is found, the `Content-Type` header is set and the serializer function is run.
The function is passed the entire `response` object, and should return either a string or an object.
If a string is returned, the `body` attribute of the response is updated.
If an object with a `body` attribute is returned, the entire response object is replaced. This is useful if you want to manipulate headers or add additional attributes in the Lambda response.
## Content Type Negotiation
The header is not the only way the middleware decides which serializer to execute.
The content type is determined in the following order:
* `event.requiredContentType` -- allows the handler to override everything else
* The `Accept` header via [accept](https://www.npmjs.com/package/accept)
* `event.preferredContentType` -- allows the handler to override the default, but lets the request ask first
* `default` middleware configuration
All options allow for multiple types to be specified in your order of preference, and the first matching serializer will be executed.
## Sample usage
```javascript
import middy from '@middy/core'
import httpResponseSerializer from '@middy/http-response-serializer'
const handler = middy((event, context) => {
const body = 'Hello World'
return cb(null, {
statusCode: 200,
body
})
})
handler
.use(httpResponseSerializer({
serializers: [
{
regex: /^application\/xml$/,
serializer: ({ body }) => `${body}`,
},
{
regex: /^application\/json$/,
serializer: ({ body }) => JSON.stringify(body)
},
{
regex: /^text\/plain$/,
serializer: ({ body }) => body
}
],
default: 'application/json'
}))
const event = {
headers: {
'Accept': 'application/xml;q=0.9, text/x-dvi; q=0.8, text/x-c'
}
}
handler(event, {}, (_, response) => {
t.is(response.body,'Hello World')
})
```
## Middy documentation and examples
For more documentation and examples, refers to the main [Middy monorepo on GitHub](https://github.com/middyjs/middy) or [Middy official website](https://middy.js.org).
## Contributing
Everyone is very welcome to contribute to this repository. Feel free to [raise issues](https://github.com/middyjs/middy/issues) or to [submit Pull Requests](https://github.com/middyjs/middy/pulls).
## License
Licensed under [MIT License](LICENSE). Copyright (c) 2017-2021 Luciano Mammino, will Farrell, and the [Middy team](https://github.com/middyjs/middy/graphs/contributors).
