JSP中Struts2映射条目的字段名称

I want to populate a map property on a Struts2 action from a JSP. What is the format of the data names that I should use? Initially I am interested in populating a Map<String, String> but in the future I would be interesting in populating a Map<String, DomainClass> where the DomainClass has properties of its own.I want to populate a map property on a Struts2