ADK6.0 : Specifying signature for an adapter service templat

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 developper for any flow service ).

Thanks for your help
Arnaud Lenfant

Did someone got the solution for this? I am almost there, but the ADK does not respond as expected.