Help with REST API on Multipart 'Content-Type'

Question

We have integrated our Salesforce instance with one of the third party app and now they want to send us a pdf file as a response in Multipart format. Below is the sample of incoming response. We want to use this Multipart 'Content-Type' data and create/upload a pdf file to the related object in Salesforce. I was wondering if someone has experience in parsing this and can help me to understand how can I process this Multipart 'Content-Type' in Apex REST or REST API. Any help is much appreciated.

Header
Content-Length=161143&Content-Type=multipart%2fform-data%3b+boundary%3d----------------------------6d848496489849&Expect=100-continue&Host=localhost%3a1251

POST DATA


05003000000D8cuI251515afagwgagaw
------------------------------6d848496489849
Content-Disposition: form-data; name="WidgetID";

Hello
------------------------------6d848496489849
Content-Disposition: form-data; name="Widgetname";

World
------------------------------6d848496489849
Content-Disposition: form-data; name="jsonData"; filename="jsonData"
Content-Type: application/json


{"widget":{"debug":"on","window":{"title":"Sample Konfabulator Widget","name":"main_window","width":500,"height":500},"image":{"src":"Images/Sun.png","name":"sun1","hOffset":250,"vOffset":250,"alignment":"center"},"text":{"data":"Click Here","size":36,"style":"bold","name":"text1","hOffset":250,"vOffset":100,"alignment":"center","onMouseUp":"sun1.opacity = (sun1.opacity / 100) * 90;"}}}
------------------------------6d848496489849


Content-Disposition: form-data; name="pdffile"; filename="pdffile"
Content-Type: application/pdf

%PDF-1.0
… PDF file…
------------------------------6d848496489849

Answer 1

The REST API does support multipart requests, but you would need to follow their requirements for inserting new records - Insert or Update Blob Data.

Apex REST Methods don't currently (Summer '17) support multipart:

Apex REST currently doesn't support requests of Content-Type multipart/form-data. Source

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One option for a custom form would be to use a Visualforce page to handle the POST request and decode the multipart data for you.

UPDATE: Unfortunately this is unable to access the actual PDF blob.

I made a very rough Visualforce page that dumped the contents of ApexPages.currentPage().getParameters() back to the page.

Visualforce page

<apex:page controller="Multipart_Controller" cache="false" showHeader="false" sidebar="false">
    <!-- Just dump the contents to show it works. 
         escape="false" is otherwise not a good idea here! -->
    <pre>
        <apex:outputText escape="false" value="{!parameterDetails}"></apex:outputText>
    </pre>
</apex:page>

Controller

public without sharing class Multipart_Controller {

    public String parameterDetails {
        get {

            if(parameterDetails == null) {
                parameterDetails = '';

                if (ApexPages.currentPage() != null){

                    Map<String, String> formData = ApexPages.currentPage().getParameters();
                    for (string key : formData.keySet()){
                        if (formData.get(key) != null){
                            parameterDetails += key + ' = ' + formData.get(key) + '\n';
                        }
                    }

                }
            }
            return parameterDetails;
        }
        private set;
    }

}

I did a test post and could see most of the POSTed form data. Note that this is a browser based tool which would have included my active cookies with sid in the request as well.

From there you could extend the Visualforce page with an init call to a controller method that would store the form data on a Custom Object with the required fields. You could then process the form data as required. Assuming you couldn't just process it directly in the controller within the heap limits.