ADK60 How to specify signature of adapter service template


I would like to know how to specify the data type of the fields in the signature of an adapter service template.

The tutorial demonstrates the use of string fields:

new String { TutorialAdapterConstant.KEY_FIELD_TYPE });

public String getKeyFieldType(){
return “string”;

But I don’t see how to specify other types of data.
If possible I’d like to use a DocumentType in the signature ( like you can do in developer for any flow service ).

Thanks for your help
Arnaud Lenfant