Question

How do you get the original filename uploaded on GAE?

Going based on the following example:

https://developers.google.com/appengine/docs/java/blobstore/overview#Uploading_a_Blob

Answer 1

Blobstore upload handler rewrites the request (removing body, adding blobkey) but leaves all other stuff untouched.

The POST mimetype is multipart/form-data, for which GAE/J offers no API to parse. So you need to use 3rd party library to parse parameters – Apache Commons-FileUpload (also as maven artifact).

Use it in your post() handler like this:

    ServletFileUpload upload = new ServletFileUpload();

    FileItemIterator iterator = null;
    try {
        iterator = upload.getItemIterator(request);
        while (iterator.hasNext()) {
            FileItemStream item = iterator.next();
            String filename = item.getName();
        }

    } catch (FileUploadException e) {
        // handle the error here
    }

Since it’s possible to upload multiple files at once you need to iterate through the set of parameters and get out the one you are interested in.