XML signature is invalid if the XML contains French character

[Tsun Yu]

Hi all,
Currently I am working on signing XML file.
The signature is valid if it contains only English.
However, if I included French characters in the file, the signature will be invalid.

I use XMLBean to create XML file and use UTF-8 to write the string into XML then sign it.
However, it does not work for me.
XMLString.newInstance().newValue(new String("préférence".getByte("UTF-8"), "UTF-8"));

Does anyone know how to solve the problem or there is any work around?

Thanks
Tsun