Hello

Can I collect data from the row flow into an array of object before calling a webservice?

Yes, you can define a array or list and store each row to the array or list on tJavaFlex component. For example:
tFileInputDelimited---row1-->tJavaFlex
     |
onsubjobok
     |
tWebserviceInput---tLogRow

on start code, define a list or array,
java.util.List<String> list=new java.util.ArrayList<String>();
on main code, store each to list or array,
list.add(row1.name);
on end code, put the list or array to global var,
  globalMap.put("list",list);

when using the list or array, you get the value by :
java.util.List list=(java.util.List)globalMap.get("list");


Best regards
Shong