Multipart/Form-Data File upload to Salesforce with APEX REST Service

Multipart/Form-Data File upload to Salesforce with APEX REST Service
Photo by Andrea De Santis / Unsplash

If you are building a client application and trying to upload a file to Salesforce using one a custom REST service, chances are you will encounter the error described in our previous article - Apex REST does not support multipart/form-data requests[SOLVED] - which discusses how multipart/form-data request handling works and the hack to build one in Salesforce. In this article we will discuss the possible options to design a REST service that can accept multipart/form-data request with files and upload to Salesforce.

All of the options that we are about to discuss will restrict the size of file that you can upload for reasons explained below in each of the option. So if you are looking for uploading heavy files (25 MB) then none of these options are suitable. You are still encouraged to read the hack so that you know what won't work and avoid re-trying these and similar options described somewhere else.

Option 1

If the client side application is setup by you yourself and you have complete control over the calling code, this hack follows our previous article and suggests to remove the content-type header and additionally pass the generated boundary as a URL parameter (to avoid discovering the boundary from the body in our apex code)

Option 2

If you have a middleware/API management tool viz. apigee and at max you can only remove the content-type header, you end up with 2 options:

Option 2.1

  • Read the incoming blob
  • Save it in a String (boom you might hit error if the attachment is so large that the EncodingUtil.base64Decode(bodyString) crosses the max string length). This applies to Option 1 as well
  • If you don't hit any limit in step#2 then go ahead and insert the content version - and optionally contentdocumentlink

Options 2.2

  • Read the incoming blob - don't save it in a String (escape the max string length error) - also do not insert the content version directly.
  • Call the standard content version api (and optionally contentdocumentlink api) - (but boom you might hit another limit error i.e.,System.CalloutException: Exceeded max size limit of 6000000 - yes the blob size counts against the HttpRequest size that has a limit of 6MB for synchronous and 12 MB for asynchronous).

Therefore to upload large size Files from a client application to Salesforce it is recommended to use and call the standard ContentVersion and optionally ContentDocumentLink API directly. Please let me know here if you are looking for an article on this.


Below are the code blocks for each of the options that we discussed above:


DZining the building blocks for Enterprise Applications


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