public static byte []
fromString(String str) {
	ByteArrayOutputStream bs = new ByteArrayOutputStream();
	byte [] raw = str.getBytes();
	for (int i = 0; i < raw.length; i++) {
		if (!Character.isWhitespace((char)raw[i]))
			bs.write(raw[i]);
	}
	byte [] in = bs.toByteArray();
	if (in.length % 2 != 0) {
		return null;
	}

	bs.reset();
	DataOutputStream ds = new DataOutputStream(bs);

	for (int i = 0; i < in.length; i += 2) {
		byte high = (byte) Base16.indexOf(Character.toUpperCase((char)in[i]));
		byte low = (byte) Base16.indexOf(Character.toUpperCase((char)in[i+1]));
		try {
			ds.writeByte((high << 4) + low);
		}
		catch (IOException e) {
		}
	}
	return bs.toByteArray();
}
Convert a hex-encoded String to binary data
@param str A String containing the encoded data
@return An array containing the binary data, or null if the string is invalid
src/main/java/core/org/xbill/DNS/utils/base16.java