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http-multipart-body-parser

Automatically parses HTTP requests with content type multipart/form-data and converts the body into an object. Also handles gracefully broken JSON as Unsupported Media Type (415 errors) if used in combination with httpErrorHandler.

It can also be used in combination with validator so that the content can be validated.

Note: by default this is going to parse only events that contain the header Content-Type (or content-type) set to multipart/form-data. If you want to support different casing for the header name (e.g. Content-type) then you should use the httpHeaderNormalizer middleware before this middleware.

Install​

To install this middleware you can use NPM:

npm install --save @middy/http-multipart-body-parser

Options​

  • busboy (object) (optional): defaults to {} and it can be used to pass extraparameters to the internal busboy instance at creation time. Checkout the official documentation for more information on the supported options.
  • charset (string) (default utf8): it can be used to change default charset. Set to binary when recieving images.
  • disableContentTypeError (boolean) (optional): Skip throwing 415 when Content-Type is invalid. Default: false.

Note: this middleware will buffer all the data as it is processed internally by busboy, so, if you are using this approach to parse significantly big volumes of data, keep in mind that all the data will be allocated in memory. This is somewhat inevitable with Lambdas (as the data is already encoded into the JSON in memory as Base64), but it's good to keep this in mind and evaluate the impact on you application. If you really have to deal with big files, then you might also want to consider to allowing your users to directly upload files to S3

Sample usage​

import middy from '@middy/core'
import httpHeaderNormalizer from '@middy/http-header-normalizer'
import httpMultipartBodyParser from '@middy/http-multipart-body-parser'

const lambdaHandler = (event, context) => {
  return {}
}

export const handler = middy()
  .use(httpHeaderNormalizer())
  .use(httpMultipartBodyParser())
  .handler(lambdaHandler)

// invokes the handler
const event = {
  headers: {
    'Content-Type':
      'multipart/form-data; boundary=----WebKitFormBoundaryppsQEwf2BVJeCe0M'
  },
  body: 'LS0tLS0tV2ViS2l0Rm9ybUJvdW5kYXJ5cHBzUUV3ZjJCVkplQ2UwTQ0KQ29udGVudC1EaXNwb3NpdGlvbjogZm9ybS1kYXRhOyBuYW1lPSJmb28iDQoNCmJhcg0KLS0tLS0tV2ViS2l0Rm9ybUJvdW5kYXJ5cHBzUUV3ZjJCVkplQ2UwTS0t',
  isBase64Encoded: true
}
handler(event, {}, (_, body) => {
  equal(body, { foo: 'bar' })
})