Use Variable in Multipart Form-Data Attachment

atepe · November 22, 2021, 4:40pm

In a POST, I need to pass a pdf file and a JSON file to tell the application some details about the pdf file. One of the properties is an environment variable “ParticipantID” that I receive in a previous call:

{
  "executionType": "E-Sign",
  "name": "Retail Installment Contract2",
  "order": 1,
  "participants": [
    {
      "participantUid": "{{ParticipantID}}",
      "required": true
    }
  ]
}

I want to just use the “{{ParticipantID}}” notation in the attachment so that I don’t have to update this file every time I run my collection but this doesn’t seem to work.

I’m following this enhancement request which would probably fix this:

github.com/postmanlabs/postman-app-support

Ability to dynamically populate an environment variable value in a Postman attachment

opened 07:00PM - 23 Sep 21 UTC

pjdjr

feature Request request-sending product/runtime request-body-format

### Is there an existing request for this feature? - [X] I have searched the ex…isting issues for this feature request ### Is your feature request related to a problem? I need to use a value from an API response in my next API request. The trick is that the request is a multi-part message with an XML attachment, and the value from the response must be placed inside the XML file. Many of the API calls I make in the QA testing of my company's product require XML attachments and are thus multi-part messages. Postman allows for file attachments, but what it seemingly cannot do is dynamically populate an environment variable value in a Postman file attachment. A tangible example: I create a transaction in my first API call and a transaction ID is returned in the response. I have no problem taking the transaction ID from response #1 and placing it an environment variable, and I know how to use the environment variable in subsequent calls by placing my variable in the Body as form-data. But, I cannot take my transaction ID and use it inside XML that is an attachment to my API call. If I put a variable in the XML file (e.g., transactionSid="{{tSid}}") I receive an error when I call the API. I recently posed this problem as a question on Stackoverflow: https://stackoverflow.com/questions/69165679/how-to-dynamically-populate-an-environment-variable-value-in-a-postman-attachmen The answer offered is beyond my current technical ability, but in any case the solution seems somewhat cumbersome considering how many API tests I would need to implement this solution for. ReadyAPI has the ability to handle this scenario fairly gracefully, and I really wish Postman could, too. This is the single-largest hurdle for me to switching to use Postman as my primary API testing tool. ### Describe the solution you'd like The ideal solution would be to make it possible to use environment variables in an XML attachment that would be populated at run-time. ### Describe alternatives you've considered I received an answer to my question on Stackoverflow. I may yet attempt to use this solution, but it is beyond my current technical ability and also seems more complicated than it should be. ReadyAPI solves for this scenario in a user-friendly way. https://stackoverflow.com/questions/69165679/how-to-dynamically-populate-an-environment-variable-value-in-a-postman-attachmen ### Additional context _No response_

I’ve also looked on stackoverflow and there seem to be some pretty complicated ways (at least for me) where instead of actually attaching a file in Postman, I could submit a string of data and use a variable there.

I’m certainly doing several things wrong in the screenshot above, but the variable doesn’t seem to be recognized and I think there are other things I need to do for this JSON object to be compatible with the multipart format.

If I can’t use the variable notation in the attachment, could I dynamically set the value in the attachment if it’s in my working directory? Or could I convert my attachment to a text string and use a variable there?

Knowing that there’s an enhancement request for this, wondering if anyone has suggestions on workarounds in the meantime.

Thank you!

atepe · January 21, 2022, 5:41pm

It turns out that Postman has very simple support for this, but the option I needed to make this work was just in a hidden column in the multipart form-data page.

What worked for me:

Expose the “Content Type” Column in form-data and set to application/json

image1534×394 39.6 KB
Change the “file” option next to the KEY to “text” and then paste the raw JSON in the VALUE

image1536×402 43.5 KB

…Of course it would be as simple as exposing a hidden column