We are using the Box Widget in our Salesforce client and this allows our users to easily upload files to Box' system. However, we also need to upload files that may have been added by users as attachments to various objects.
Every example I've seen so far shows a Rest service sending a form POST where the intended file was received from within the browser using tags (input Type=File). However, the apex method wasn't initiated by a browser form.
Certainly we can retrieve the Attachment object, and I know how to create a Rest Service to call Box's API, but I don't know how to simulate a file upload when we only have apex Blobs to send.