In this blog post, we are going to discuss on how the feature to upload the avatar for a user was implemented on the SUSI.AI Server. The API endpoint by which a user can upload his/her avatar image is https://api.susi.ai/aaa/uploadAvatar.json.

• The endpoint is of POST type.
• It accepts two request parameters –
• image – It contains the entire image file sent from the client
• access_token – It is the access_token for the user

The minimalUserRole is set to USER for this API, as only logged-in users can use this API.

Going through the API development

• The image and access_token parameters are first extracted via the req object, that is passed to the main function. The  parameters are then stored in variables.

• There is a check if the access_token and image exists. It it doesn’t, an error is thrown.

• This code snippet discusses the above two points –

protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    Part imagePart = req.getPart("image");
    if (req.getParameter("access_token") != null) {
        if (imagePart == null) {
            result.put("accepted", false);
            result.put("message", "Image file not received");
        } else {
            ….
        }
    else{
        result.put("message","Access token are not given");
        result.put("accepted",false);
        resp.setContentType("application/json");
        resp.setCharacterEncoding("UTF-8");
        resp.getWriter().write(result.toString());
    }
}

• Then the input stream is extracted from the imagePart and stored. And post that the identity is checked if it is valid.

• The input stream is converted into the Image type using the ImageIO.read method.

• The image is eventually converted into a BufferedImage using a function, described below.

public static BufferedImage toBufferedImage(Image img)
{
    if (img instanceof BufferedImage)
        return (BufferedImage) img;

    // Create a buffered image with transparency
    BufferedImage bimage = new BufferedImage(img.getWidth(null),     
    img.getHeight(null), BufferedImage.TYPE_INT_ARGB);
    // Draw the image on to the buffered image
    Graphics2D bGr = bimage.createGraphics();
    bGr.drawImage(img, 0, 0, null);
    bGr.dispose();
    // Return the buffered image
    return bimage;
}

• After that, the file path and name is set. The avatar for each user is stored in the /data/avatar_uploads/<uuid of the user>.jpg.

• The avatar is written to the path using the ImageIO.write function. Once, the file is stored on the server, the success response is sent and the client side receives it.

Resources

• Source of the API – https://github.com/fossasia/susi_server/blob/development/src/ai/susi/server/api/aaa/UploadAvatarService.java