Question

I need to upload a file in GWT in the background, ie. not from a visual widget.

For this I’ve found the RequestBuilder class, but little documentation on how to use it for upload purposes.

The file content I need to upload is 100% plaintext.

My code so far looks like this:

final String filename = UUID.randomUUID().toString() + ".txt";

RequestBuilder rb = new RequestBuilder(RequestBuilder.POST, "http://localhost/upload");
rb.setRequestData(selected.getBody()); // getBody() is plain-text
rb.setHeader("Content-Type", "application/x-www-form-urlencodeddata");
rb.setCallback(new RequestCallback() {
    @Override
    public void onResponseReceived(Request request, Response response) {
        w.setUrl("http://localhost/magic.html?hide=status&open=" + filename);
        w.show();
        w.maximize();                            
    }

    @Override
    public void onError(Request request, Throwable exception) {
        exception.printStackTrace();
    }
});

// Checked Exceptions sucks *sigh*
try {
    rb.send();
}
catch (RequestException e) {
    e.printStackTrace();
}

I hope someone can give me some pointers towards solving this issue, thanks!

Answer 1

I think it’s not possible to upload files to the server without user interaction using JavaScript only. I think it’s blocked by the browser, because it would mean anybody could upload any file from your system when you visit a site, which would be a major security problem. I don’t know why you would want to do this, but I guess you need to look at another approach to what you are trying to do.