Java Clipboard: Paste HTML from Firefox on Linux

Question

I have a strange problem when pasting HTML from Firefox into a Java6 app (only!) on Linux. Here is a minimal example:

import java.awt.Toolkit;
import java.awt.datatransfer.Clipboard;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.Transferable;
import java.io.Reader;
import java.nio.ByteBuffer;

class ClipboardPrinter {
    public static void main( String args[] ) throws Exception
    {
        Clipboard systemClipboard = Toolkit.getDefaultToolkit()
                .getSystemClipboard();
        Transferable transferData = systemClipboard.getContents(null);
        if (transferData == null) {
            System.out.println("no content");
            return;
        }

//      final DataFlavor htmlFlavorString = new DataFlavor("text/html;class=java.lang.String");
//      String html = (String)transferData.getTransferData(htmlFlavorString);
//      System.out.println("html = '" + html + "'");

        final DataFlavor htmlFlavor = new DataFlavor("text/html;class=java.nio.ByteBuffer;charset=US-ASCII");
        if (!transferData.isDataFlavorSupported(htmlFlavor)) {
            System.out.println("no text/html reader content");
            return;
        }

        ByteBuffer bb = (ByteBuffer)transferData.getTransferData(htmlFlavor);
        byte[] bytes = bb.array();
        for (byte b: bytes)
        {
            System.out.format("%02x", b);
        }
        System.out.println();
        final int cutoff = 2;
        byte[] bytes2 = new byte[bytes.length - cutoff];
        for (int i = cutoff; i < bytes.length; i++)
            bytes2[i-cutoff] = bytes[i];
        final String htmlContent = new String(bytes2, "UTF-16LE");


        System.out.println("htmlContent = '" + htmlContent + "'");
    }
}

First I tried to use new DataFlavor("text/html;class=java.lang.String"), (code commented out in above snippet), but this results in an unusable String with 2 chars with value 65533 at the beginning (and it does not help to cut off those two characters).

Next I used a ByteBuffer data flavor with charset=US-ASCII (I used ASCII on purpose!): charset=UTF-16LE (or UTF-16 or UTF-16BE) does not work at all. With the above charset=US-ASCII solution (along with new String(bytes2, "UTF-16LE")), 7bit characters work (but e.g. umlauts don't work, a '?' gets printed instead).

I cut off two bytes because there seem to be two boms at the beginning (not sure, could be something else)?

I get a similar result with a data flavor with charset=UTF-8 and cutoff=6 (two three-byte "replacement characters" 0xEFBFBD at the beginning and umlaut encoded as two wrong characters). In both cases I used new String(bytes2, "UTF-16LE").

Do you have any suggestions about how to:

• support non-ASCII characters in this solution (or find a better solution)?
• determine whether it's UTF-16LE or UTF-16BE?

Thank you! Any hints are appreciated!

BTW: Here are the supported data flavors on my (Linux) system (from transferable.getTransferDataFlavors()):

[java.awt.datatransfer.DataFlavor[mimetype=text/html;representationclass=java.io.Reader]
java.awt.datatransfer.DataFlavor[mimetype=text/html;representationclass=java.lang.String]
java.awt.datatransfer.DataFlavor[mimetype=text/html;representationclass=java.nio.CharBuffer]
java.awt.datatransfer.DataFlavor[mimetype=text/html;representationclass=[C]
java.awt.datatransfer.DataFlavor[mimetype=text/html;representationclass=java.io.InputStream;charset=UTF-16]
java.awt.datatransfer.DataFlavor[mimetype=text/html;representationclass=java.nio.ByteBuffer;charset=UTF-16]
java.awt.datatransfer.DataFlavor[mimetype=text/html;representationclass=[B;charset=UTF-16]
java.awt.datatransfer.DataFlavor[mimetype=text/html;representationclass=java.io.InputStream;charset=UTF-8]
java.awt.datatransfer.DataFlavor[mimetype=text/html;representationclass=java.nio.ByteBuffer;charset=UTF-8]
java.awt.datatransfer.DataFlavor[mimetype=text/html;representationclass=[B;charset=UTF-8]
java.awt.datatransfer.DataFlavor[mimetype=text/html;representationclass=java.io.InputStream;charset=UTF-16BE]
java.awt.datatransfer.DataFlavor[mimetype=text/html;representationclass=java.nio.ByteBuffer;charset=UTF-16BE]
java.awt.datatransfer.DataFlavor[mimetype=text/html;representationclass=[B;charset=UTF-16BE]
java.awt.datatransfer.DataFlavor[mimetype=text/html;representationclass=java.io.InputStream;charset=UTF-16LE]
java.awt.datatransfer.DataFlavor[mimetype=text/html;representationclass=java.nio.ByteBuffer;charset=UTF-16LE]
java.awt.datatransfer.DataFlavor[mimetype=text/html;representationclass=[B;charset=UTF-16LE]
java.awt.datatransfer.DataFlavor[mimetype=text/html;representationclass=java.io.InputStream;charset=ISO-8859-1]
java.awt.datatransfer.DataFlavor[mimetype=text/html;representationclass=java.nio.ByteBuffer;charset=ISO-8859-1]
java.awt.datatransfer.DataFlavor[mimetype=text/html;representationclass=[B;charset=ISO-8859-1]
java.awt.datatransfer.DataFlavor[mimetype=text/html;representationclass=java.io.InputStream;charset=US-ASCII]
java.awt.datatransfer.DataFlavor[mimetype=text/html;representationclass=java.nio.ByteBuffer;charset=US-ASCII]
java.awt.datatransfer.DataFlavor[mimetype=text/html;representationclass=[B;charset=US-ASCII]
java.awt.datatransfer.DataFlavor[mimetype=application/x-java-serialized-object;representationclass=java.lang.String]
java.awt.datatransfer.DataFlavor[mimetype=text/plain;representationclass=java.io.Reader]
java.awt.datatransfer.DataFlavor[mimetype=text/plain;representationclass=java.lang.String]
java.awt.datatransfer.DataFlavor[mimetype=text/plain;representationclass=java.nio.CharBuffer]
java.awt.datatransfer.DataFlavor[mimetype=text/plain;representationclass=[C]
java.awt.datatransfer.DataFlavor[mimetype=text/plain;representationclass=java.io.InputStream;charset=unicode]
java.awt.datatransfer.DataFlavor[mimetype=text/plain;representationclass=java.nio.ByteBuffer;charset=UTF-16]
java.awt.datatransfer.DataFlavor[mimetype=text/plain;representationclass=[B;charset=UTF-16]
java.awt.datatransfer.DataFlavor[mimetype=text/plain;representationclass=java.io.InputStream;charset=UTF-8]
java.awt.datatransfer.DataFlavor[mimetype=text/plain;representationclass=java.nio.ByteBuffer;charset=UTF-8]
java.awt.datatransfer.DataFlavor[mimetype=text/plain;representationclass=[B;charset=UTF-8]
java.awt.datatransfer.DataFlavor[mimetype=text/plain;representationclass=java.io.InputStream;charset=UTF-16BE]
java.awt.datatransfer.DataFlavor[mimetype=text/plain;representationclass=java.nio.ByteBuffer;charset=UTF-16BE]
java.awt.datatransfer.DataFlavor[mimetype=text/plain;representationclass=[B;charset=UTF-16BE]
java.awt.datatransfer.DataFlavor[mimetype=text/plain;representationclass=java.io.InputStream;charset=UTF-16LE]
java.awt.datatransfer.DataFlavor[mimetype=text/plain;representationclass=java.nio.ByteBuffer;charset=UTF-16LE]
java.awt.datatransfer.DataFlavor[mimetype=text/plain;representationclass=[B;charset=UTF-16LE]
java.awt.datatransfer.DataFlavor[mimetype=text/plain;representationclass=java.io.InputStream;charset=ISO-8859-1]
java.awt.datatransfer.DataFlavor[mimetype=text/plain;representationclass=java.nio.ByteBuffer;charset=ISO-8859-1]
java.awt.datatransfer.DataFlavor[mimetype=text/plain;representationclass=[B;charset=ISO-8859-1]
java.awt.datatransfer.DataFlavor[mimetype=text/plain;representationclass=java.io.InputStream;charset=US-ASCII]
java.awt.datatransfer.DataFlavor[mimetype=text/plain;representationclass=java.nio.ByteBuffer;charset=US-ASCII]
java.awt.datatransfer.DataFlavor[mimetype=text/plain;representationclass=[B;charset=US-ASCII]
java.awt.datatransfer.DataFlavor[mimetype=text/x-moz-url-priv;representationclass=java.io.InputStream]
java.awt.datatransfer.DataFlavor[mimetype=text/_moz_htmlinfo;representationclass=java.io.InputStream]
java.awt.datatransfer.DataFlavor[mimetype=text/_moz_htmlcontext;representationclass=java.io.InputStream]
java.awt.datatransfer.DataFlavor[mimetype=text/x-moz-url-priv;representationclass=java.nio.ByteBuffer]
java.awt.datatransfer.DataFlavor[mimetype=text/_moz_htmlinfo;representationclass=java.nio.ByteBuffer]
java.awt.datatransfer.DataFlavor[mimetype=text/_moz_htmlcontext;representationclass=java.nio.ByteBuffer]
java.awt.datatransfer.DataFlavor[mimetype=text/x-moz-url-priv;representationclass=[B]
java.awt.datatransfer.DataFlavor[mimetype=text/_moz_htmlinfo;representationclass=[B]
java.awt.datatransfer.DataFlavor[mimetype=text/_moz_htmlcontext;representationclass=[B]]

Answer 1

I belive the problem is related due to the fact that he read from clipboard as US-ASCII, then convert to unicode and expect to leave German umlauts intact. As US-ASCII is a 7-bit charset German umlauts are not included and already lost after reading the clipboard as US-ASCII.

public class CharsetDemo {
    public static void main(String[] args) throws Exception {
        byte[] bytes;

        // convert the German umlaut to bytes in US-ASCII charset
        bytes = "ö".getBytes("US-ASCII");
        System.out.println("US-ASCII");
        System.out.println("bytes : " + asHexString(bytes));
        System.out.println("string: " + new String(bytes, "US-ASCII"));
        System.out.println();

        // create a unicode string from the US-ASCII bytes
        String utf8String = new String(bytes, "UTF-8");
        bytes = utf8String.getBytes("UTF-8");
        System.out.println("UTF-8");
        System.out.println("bytes : " + asHexString(bytes));
        System.out.println("string: " + utf8String);
        System.out.println();

        // convert the German umlaut to bytes in ISO-8859-1 charset
        bytes = "ö".getBytes("ISO-8859-1");
        System.out.println("ISO 8859-1");
        System.out.println("bytes : " + asHexString(bytes));
        System.out.println("string: " + new String(bytes, "ISO-8859-1"));
        System.out.println();

        // create a unicode string from the ISO-8859-1 bytes
        utf8String = new String(bytes, "UTF-8");
        bytes = utf8String.getBytes("UTF-8");
        System.out.println("UTF-8");
        System.out.println("bytes : " + asHexString(bytes));
        System.out.println("string: " + utf8String);
        System.out.println();

        // bytes of the "REPLACEMET CHARACTER"
        System.out.println("replacement character bytes: " 
            + asHexString("\uFFFD".getBytes("UTF-8")));

    }

    static String asHexString(byte[] bytes) {
        StringBuilder sb = new StringBuilder();
        for (byte b : bytes) {
            sb.append(String.format("%X ", b));
        }
        return sb.toString();
    }
}

output

US-ASCII
bytes : 3F 
string: ?  <--- the question mark represents here the "REPLACEMENT CHARACTER"

UTF-8
bytes : 3F 
string: ?

ISO 8859-1
bytes : F6 
string: ö

UTF-8
bytes : EF BF BD  <-- the "REPLACEMENT CHARACTER", as "F6" is not a valid UTF-8 codepoint
string: �

replacement character bytes: EF BF BD