uploading a file to Rails JSON API server with Paperclip and Multipart request

Question

I want to upload a file from an Android client to a Rails JSON API server.

I'm sending a Multipart/form request from the Android client which looks like that:

Content-Type: multipart/form-data; boundary=d99ArGa2SaAsrXaGL_AdkNlmGn2wuflo5
Host: 10.0.2.2:3000
Connection: Keep-Alive
User-Agent: Apache-HttpClient/UNAVAILABLE (java 1.4)

--d99ArGa2SaAsrXaGL_AdkNlmGn2wuflo5
Content-Disposition: form-data; name="POSTDATA"
Content-Type: application/json; charset=UTF-8
Content-Transfer-Encoding: 8bit

{"tags":["test"],"location_id":1,"post":{"content":"test"}}
--d99ArGa2SaAsrXaGL_AdkNlmGn2wuflo5
Content-Disposition: form-data; name="IMAGEDATA"; filename="testimage.jpg"
Content-Type: image/jpeg
Content-Transfer-Encoding: binary

<BINARY DATA?
--d99ArGa2SaAsrXaGL_AdkNlmGn2wuflo5--

in the rails controller i'm creating the new post with this code:

@parsed_json = JSON(params[:POSTDATA])
@post = @current_user.posts.new(@parsed_json["post"])

how do I make Paperclip save the attachment from the multipart form ?

I can do it with something like this:

if params.has_key?(:IMAGEDATA)
    photo = params[:IMAGEDATA]
    photo.rewind

    @filename = "/tmp/tempfile"
    File.open(@filename, "wb") do |file|
      file.write(photo.read)
    end

    @post.photo = File.open(@filename)
  end

but it doesn't look like the best solution, also, the filename that is being passed in ther multipart request is not used.

score 12 · Answer 1 · answered Mar 29 '13 at 16:49

The pure json way to do this is to not pass content-type multipart-form and pass the file as a base64 encoded string in the json.

I figured this out thanks this post: http://www.rqna.net/qna/xyxun-paperclip-throws-nohandlererror-with-base64-photo.html

Here's an example of the json:

"{\"account\":{\"first_name\":\"John\",\"last_name\":\"Smith\",\"email\":\"john@test.com\",\"password\":\"testtest\",\"avatar\":{\"data\":\"INSERT BASE64 ENCODED STRING OF FILE HERE\",\"filename\":\"avatar.jpg\",\"content_type\":\"image/jpg\"}}}"

Then in the controller process the incoming avatar like this before saving the model.

def process_avatar
  if params[:account] && params[:account][:avatar]
    data = StringIO.new(Base64.decode64(params[:account][:avatar][:data]))
    data.class.class_eval { attr_accessor :original_filename, :content_type }
    data.original_filename = params[:account][:avatar][:filename]
    data.content_type = params[:account][:avatar][:content_type]
    params[:account][:avatar] = data
  end
end

This is working so far. I am fine, but can somebody explain me how this can work, that we actually filling params[:account][:avatar] with StringIO class? — Jakub Kuchar, Nov 22 '13 at 09:44
This is half working for me, if the picture is too large and so is the base64 string then it crashes and raise the Errno::E2BIG exception. — Sylvain Kalache, Feb 03 '14 at 01:31
I think it's more clean to more this logic to the model as documented here: http://eggie5.com/54-ios-rails-image-uploads — eggie5, Aug 28 '14 at 18:39

score 4 · Answer 2 · edited May 23 '17 at 11:48

So, I'm guessing your Post model looks something like this:

class Post < ActiveRecord::Base
  has_attached_file :photo, :styles => { ... }
  ...
end

So you should be able to do something as simple as this:

@post.photo = params[:IMAGEDATA] if params[:IMAGEDATA].present?
@post.save if @post.valid?

And it should save the photo.

If you need to do something more complicated, try re-arranging the form data into the data that the format Paperclip expects. And if you need to dig deeper, take a look inside Paperclip's Paperclip::Attachment class.

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uploading a file to Rails JSON API server with Paperclip and Multipart request

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