Drag and drop file upload on TreeTable

I wish to drag and drop multiple files from outside the browser (from OS file system) on to a row in a TreeTable so that files get uploaded and get added as children to the row dropped on in the TreeTable.

I referred to below code sample which allows drag and drop of files onto a imageBox:
https://dev.vaadin.com/svn/demo/sampler/src/com/vaadin/demo/sampler/features/dragndrop/DragDropHtml5ToFromDesktopExample.java

How can I have drag and drop of files to a row in a TreeTable and handle the uploaded files?

Please help by providing some direction on how it can be done. Thanks in advance.

Thanks,
Nikhil