Is it possible to pass File Object to AWS Lambda through API Gataway in javascript?

user_13198934 0
Viewed 824

Is it possible to pass JavaScript File Object from browser to AWS Lambda through API Gateway (finally to S3). I am using TypeScript and React.

Environment

Frontend

  • TypeScript
  • React
  • AWS Amplify (to use API module)

Backend(AWS Lambda)

  • Node.js

What's expected

to pass File Object, which got from browser by <input type='file'>, to backend aws lambda through API Gateway.

What's happening

console.log(event) at backend, the log output was empty.

What I want to know

the way how to pass File Object(Blob) to lambda correctly. (Just a link to document, it'll also really help me.)

Code (Frontend)

import { API } from 'aws-amplify'
...
const file = { body: this.state.file }
console.log(file) // output was collect File Object at this time
API.post(<API_NAME>, <PATH>, file)
  .then(response => {
    console.log(response)
  }).catch(error => {
    console.log(error)
  })

Code (Backend)

exports.lambdaHandler = function (event, context, callback) {
  console.info(`event.body: ${event.body}`) // got `event.body: {}` at Cloud Watch Logs
  ...
}

Is it possible what I'm trying to do by setting Content-Type or something? (I couldn't find any documentation. I've been started programming just only for one year).

aws-lambda typescript reactjs javascript
2 Answers

I disagree with sidali's answer for many reasons (security, cost, ...). You would not want a publicly accessible S3 bucket.

It is recommended to request a presigned URL for S3 over your API Gateway + Lambda. With that URL only the specific user would be able to upload a file for a defined period of time (e.g., 1 minute or 5 hours).

const getSignedUrlForUpload = async () => {
  const params = {
    Bucket: BUCKET_NAME,
    Key: 'AWS_Cloud_Best_Practices.pdf',
    Expires: 60,
    ContentType: 'application/pdf',
  }


  const url = await new Promise((resolve, reject) => {
    s3.getSignedUrl('putObject', params, (err, url) => {
      if (err) reject(err)

      resolve(url)
    })
  })

  return url
}

uploadFileToS3()
  .then((res) => {
    console.log(res)
  }).catch((e) => {
    console.log(e)
  })

Source: https://arpadt.com/articles/presigned-urls-in-node#34-upload-link

user_63609550

You have to upload you file into s3 directly to a specific Bucket, and create lambda trigger event on s3 upload on this particular Bucket,

This way lambda will trigger each time you send a file, you can there read your file and do your process.

Please read https://docs.aws.amazon.com/lambda/latest/dg/with-s3.html

user_15543400
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