Camunda 8.7 SaaS File Upload using REST Connector

[mbarni]

I’ve created a REST Connector Task that should send a file according to the documentation in base64 in the body in a JSON format.

The body in my REST Connector:

{
“someData”: “something”,
“fileName”: documents[1].metadata.fileName
“base64”: documents[1]
}

Instead of converting the “documents[1]” to base64 - documents is a variable coming out of a file picker in Camunda 8 Form - Camunda connector is sending just the JSON pointing to the file.

Camunda 8 Rest Connector documentation does not seem to be right.

[aravindhrs]

@mbarni , The Camunda 8 REST Connector does not automatically convert documents[1] (from File Picker or Webhook) to a base64-encoded string in the request body—even though the documentation implies it might.

Instead, documents[1] is just a reference object, containing the document ID and metadata, not the file content.

Why This Happens

When you use a File Picker in Camunda 8 or upload a file via Webhook:

• Camunda stores the file in its Document Store.
• The documents[1] variable looks like this:

{
  "id": "01HT...",
  "metadata": {
    "fileName": "test.pdf",
    ...
  }
}

This object does not include the binary content or a base64 string.

How to Actually Send the File Content via REST Connector

To send the file content in base64 as part of the JSON body, you must do the following manually:

Use a Webhook/Integration Layer (Recommended for SaaS)

If you’re using Camunda SaaS and can’t write custom workers, create a lightweight middleware:

1. Your REST Connector sends the document.id.
2. The middleware fetches and base64-encodes the file.
3. It sends the final request to the destination system.

You can implement this in a serverless function (e.g., AWS Lambda, Google Cloud Function) or Express/Flask service.

[mbarni]

Documentation does not “implies” anything. It states it.
So the documentation is wrong?!

When I use a local Camunda 8.7 Run, I am able to test this but then the Document Store is “in memory”, so reading the file gives me incident.

Thanks for the reply.