Uploading Files

In digital health, a common requirement is to upload PDFs or other files from one system to another. Examples include:

• Uploading pathology reports into a legacy EHR
• Uploading service requisitions into an SFTP server

In this guide, we will show you how to:

• Create and upload a PDF file from a Bot to an HTTP endpoint
• Upload a file form a to an SFTP server

You can find complete example bots for these examples in the Medplum Demo Bots repo

HTTP File Uploads

To upload to a file using http, you will have to submit an HTTP request with the Content-Type multipart/form-data. Medplum Bots ship with the npm form-data package to make it easier to create form data.

Let's take a look at an example. First, we'll create a pdf (see the Create a PDF tutorial for more details)

const binary = await medplum.createPdf({
  content: ['Hello Medplum'],
});
console.log('Binary result', JSON.stringify(binary, null, 2));

medplum.createPdf() creates a Binary resource and stores it on the Medplum server. Our next step will be to download the resulting PDF data, and convert it to a stream to send to our 3rd party API.

// Download the PDF
const pdfData = await medplum.download(binary.url);
const pdfStream = await pdfData.stream();

Next, we'll construct the request body using the form-data library

// Create a multipart form body
const form = new FormData();
form.append('otherValue', 'hello medplum');
form.append('testPdf', pdfStream);

And lastly, we'll post the form to the API (here, we're just using httpbin) as an example

// Post the form
const response = await fetch('https://httpbin.org/post', {
  method: 'POST',
  body: form,
  headers: form.getHeaders(),
});

This is what it looks like all put together. You can also see this example in our Medplum Demo Bots repo.

import { BotEvent, MedplumClient } from '@medplum/core';
import fetch from 'node-fetch';
import FormData from 'form-data';

export async function handler(medplum: MedplumClient, event: BotEvent): Promise<any> {
  // Create the PDF
  const binary = await medplum.createPdf({
    content: ['Hello Medplum'],
  });
  console.log('Binary result', JSON.stringify(binary, null, 2));

  if (!binary.url) {
    throw new Error('Binary is missing');
  }

  // Download the PDF
  const pdfData = await medplum.download(binary.url);
  const pdfStream = await pdfData.stream();

  // Create a multipart form body
  const form = new FormData();
  form.append('otherValue', 'hello medplum');
  form.append('testPdf', pdfStream);

  // Post the form
  const response = await fetch('https://httpbin.org/post', {
    method: 'POST',
    body: form,
    headers: form.getHeaders(),
  });

  // Show the JSON response
  const json = await response.json();
  console.log('response', json);
  return json;
}

SFTP Uploads

Medplum Bots provide the ssh2-sftp-client library to connect to SFTP servers. You can reference the library's github page for detailed documentation on how it works.

Below is an example bot that connects to an SFTP server and returns a list of all available files at the root directory.

import { BotEvent, MedplumClient } from '@medplum/core';
import Client from 'ssh2-sftp-client';

export async function handler(medplum: MedplumClient, event: BotEvent): Promise<any> {
  console.log('SFTP test');
  let data: any | undefined = undefined;
  try {
    const sftp = new Client();
    // Connect to the SFTP server
    // 'test.rebex.net' is a publicly available test server
    await sftp.connect({
      host: 'test.rebex.net',
      username: 'demo',
      password: 'password',
    });
    data = await sftp.list('.');
    console.log('data', data);
  } catch (err) {
    console.log('error', err);
    return false;
  }
  return data;
}