REST file transfer.md

incomplete and barely proven comparison of file transfer methods with REST

JSON with base64

$ curl -X POST -d @content.json -H "Content-Type: application/json" -H "Accept: application/json" http://localhost/
$ cat content.json
{  
   "files":{  
      "main.tex":"XGRvY3VtZW50Y2xhc3N7YXJ0aWNsZX0KXGJlZ2lue2RvY3VtZW50fQpcaW5jbHVkZXt0ZXN0L3Rlc3R9ClxlbmR7ZG9jdW1lbnR9",
      "test/test.tex":"aGFsbG8gd2VsdA=="
   }
}

• One request for all files (might be easier handling on consumer side)
• Increases file size by about 33% (👎 bad for big files, 🤷‍ does not matter much for small files and low traffic)
• If POST transfers back a processed result, this might lead to a synchronous style which is not very REST-y. (But also might be acceptable, because it is easier; and does not matter if no scalability is required)
• With a synchronous style, server can just delete all files after processing (or only retain the result file).

Multiple POST

$ curl -X POST -d @file1 -H http://localhost/files/
$ curl -X POST -d @file2 -H http://localhost/files/

• Transfering each resource on its own is more REST-y
• If file processing is wanted, an additional GET is needed (and probably some description file which points to all previously uploaded files).
• If files are only needed temporarily, server has to handle some garbage collection.

Multipart

Content-Type: multipart/form-data; boundary=12345

--12345
Content-Disposition: form-data; name="sometext"

some text that you wrote in your html form ...
--12345
Content-Disposition: form-data; name="name_of_post_request" filename="filename.xyz"

content of filename.xyz that you upload in your form with input[type=file]
--12345
Content-Disposition: form-data; name="image" filename="picture_of_sunset.jpg"

content of picture_of_sunset.jpg ...
--12345--

• Sometimes badly supported by libraries.
• Not very intuitive and beautiful; rather error prone.
• No idea if a path separator in filename would be legal.
• A simple HTML page without JavaScript could be used to transfer data.