JTable, JList, and JTree were designed to give drag-over feedback when a drag operation occurs within their bounds. They are supposed to update their selection to show where a potential drop will occur.

Since JTable, JList, and JTree don't have built-in drop support, one must install a custom TransferHandler to support drop. We describe how to do this in our Swing DnD documentation. In fact, I came across this bug while trying to write a simple example for an article of how to implement DnD in a JList. Unfortunately, due to a bug, installing a custom TransferHandler clobbers the built-in drag-over feedback.