swing.edt {
            frame(  id: 'mainFrame',
                    title: 'title',
                    defaultCloseOperation: JFrame.EXIT_ON_CLOSE,
                    show: true,
                    size: [300, 300]) {
                textLabel = label(text:"Drag file here", constraints:BL.NORTH)
                mainFrame.dropTarget = [
                        drop: { dtde ->
                            def t = dtde.transferable
                            if (t.isDataFlavorSupported(DataFlavor.javaFileListFlavor)) {
                                dtde.acceptDrop(DnDConstants.ACTION_REFERENCE)
                                t.getTransferData(DataFlavor.javaFileListFlavor).each {
                                    println it
                                }
                            }
                        }
                ] as DropTarget
            }
        }