The Custom Encoder supports elements of binary data type, as well as String data type. Far an element field of binary data type, the data type of “hexBinary” or “base64Binary” can be specified in the XML schema using the XSD editor.
Note that, base64 encoded data expands by a factor of 1.33 times the original size, and hexadecimal encoded data expands by a factor of 2 times original size, assuming an underlying UTF-8 text encoding in both cases. If the underlying text encoding is UTF-16, then these numbers double.