Missing HFS promise error: Drag and Drop from Apple Mail app to Java app works in Windows but not in OSX environment

Question

import java.awt.*;

import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.Transferable;
import java.awt.dnd.DnDConstants;
import java.awt.dnd.DropTarget;
import java.awt.dnd.DropTargetDragEvent;
import java.awt.dnd.DropTargetDropEvent;
import java.awt.dnd.DropTargetEvent;
import java.awt.dnd.DropTargetListener;
import java.io.File;
import java.util.ArrayList;

import javax.swing.*;

public class DragDropNewActivity extends JFrame implements DropTargetListener {

DropTarget dt;

public DragDropNewActivity()
{       
    setSize(400,300);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    JLabel lblDraganddrop = new JLabel("Drag And Drop here");
    lblDraganddrop.setHorizontalTextPosition(SwingConstants.CENTER);
    lblDraganddrop.setHorizontalAlignment(SwingConstants.CENTER);
    lblDraganddrop.setFont(new Font("Tahoma",Font.PLAIN,32));
    getContentPane().add(lblDraganddrop, BorderLayout.CENTER);


    dt = new DropTarget (lblDraganddrop, this);
    setVisible(true);

}
    @Override
    public void drop(DropTargetDropEvent dtde)
    {
    try
    {
        Transferable tr = dtde.getTransferable();
        DataFlavor[] flavors = tr.getTransferDataFlavors();
        ArrayList<File> fileNames = new ArrayList<File>();
        for (int i = 0; i < flavors.length; i++)
        {
        if (flavors[i].isFlavorJavaFileListType())
        {
            dtde.acceptDrop(DnDConstants.ACTION_COPY_OR_MOVE);
            @SuppressWarnings("unchecked")
            java.util.List<File> files = (java.util.List<File>) tr.getTransferData(flavors[i]);

            for (int k = 0; k < files.size(); k++)
            {
            fileNames.add(files.get(k));
            // Write the filename/s on console output.
             System.out.println(files.get(k));  

            //Parse through new file
            //new DragDropNewActivityParse().parseThroughFile(files.get(k));

            }

            dtde.dropComplete(true);
        }
        }

    }
    catch (Throwable t)
    {
        t.printStackTrace();
    }
    dtde.rejectDrop();

    }

    @Override
    public void dragEnter(DropTargetDragEvent dtde)
    {}

    @Override
    public void dragOver(DropTargetDragEvent dtde)
    {}

    @Override
    public void dropActionChanged(DropTargetDragEvent dtde)
    {}

    @Override
    public void dragExit(DropTargetEvent dte)
    {}

}

In windows it works without problem. In Mac OS HighSierra(13.4) it does not accept file from Apple Mail app. Missing HFS promise error is written in console everytime one tries to drop a file from Apple Mail app.

Console output: 2018-04-19 10:07:24.237 java[91646:4228080] Couldn't get a copy of an HFS Promise from the pasteboard 2018-04-19 10:07:24.238 java[91646:4228080] Looked for HFSPromises on the pasteboard, but found none.

File dropped from Desktop for example would be accepted. Any ideas?