Casts the string representation of a value into a type recognized by
this type handler. This method is used to translate nullValue values
into types that can be appropriately compared. If your custom type handler
cannot support nullValues, or if there is no reasonable string representation
for this type (e.g. File type), you can simply return the String representation
as it was passed in. It is not recommended to return null, unless null was passed
in.
